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Overview
Comment: | Remove dead code from the pager. |
---|---|
Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | mistake |
Files: | files | file ages | folders |
SHA1: |
7cbe175a69738499f9218ec56f1a39f0 |
User & Date: | drh 2010-07-03 12:26:33.000 |
Original Comment: | Remove code accidently appended to pager.c. |
Context
2010-07-03
| ||
13:45 | Fix an assert in pager.c. And various test cases that fail with the in-memory journal permutation. (Closed-Leaf check-in: 78fc35ff4b user: dan tags: mistake) | |
12:31 | Cherry-pick the correct changes out of the recent "mistake" branch while omitting the bugs. (check-in: 48bf309391 user: drh tags: trunk) | |
12:26 | Remove dead code from the pager. (check-in: 7cbe175a69 user: drh tags: mistake) | |
12:00 | Print the SQLite source_id() string when running speed tests. (check-in: 6d7640edcd user: drh tags: mistake) | |
Changes
Added src/pager.c.
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> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 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> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 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> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 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2001 September 15 ** ** The author disclaims copyright to this source code. In place of ** a legal notice, here is a blessing: ** ** May you do good and not evil. ** May you find forgiveness for yourself and forgive others. ** May you share freely, never taking more than you give. ** ************************************************************************* ** This is the implementation of the page cache subsystem or "pager". ** ** The pager is used to access a database disk file. It implements ** atomic commit and rollback through the use of a journal file that ** is separate from the database file. The pager also implements file ** locking to prevent two processes from writing the same database ** file simultaneously, or one process from reading the database while ** another is writing. */ #ifndef SQLITE_OMIT_DISKIO #include "sqliteInt.h" #include "wal.h" /* ******************** NOTES ON THE DESIGN OF THE PAGER ************************ ** ** Within this comment block, a page is deemed to have been synced ** automatically as soon as it is written when PRAGMA synchronous=OFF. ** Otherwise, the page is not synced until the xSync method of the VFS ** is called successfully on the file containing the page. ** ** Definition: A page of the database file is said to be "overwriteable" if ** one or more of the following are true about the page: ** ** (a) The original content of the page as it was at the beginning of ** the transaction has been written into the rollback journal and ** synced. ** ** (b) The page was a freelist leaf page at the start of the transaction. ** ** (c) The page number is greater than the largest page that existed in ** the database file at the start of the transaction. ** ** (1) A page of the database file is never overwritten unless one of the ** following are true: ** ** (a) The page and all other pages on the same sector are overwriteable. ** ** (b) The atomic page write optimization is enabled, and the entire ** transaction other than the update of the transaction sequence ** number consists of a single page change. ** ** (2) The content of a page written into the rollback journal exactly matches ** both the content in the database when the rollback journal was written ** and the content in the database at the beginning of the current ** transaction. ** ** (3) Writes to the database file are an integer multiple of the page size ** in length and are aligned to a page boundary. ** ** (4) Reads from the database file are either aligned on a page boundary and ** an integer multiple of the page size in length or are taken from the ** first 100 bytes of the database file. ** ** (5) All writes to the database file are synced prior to the rollback journal ** being deleted, truncated, or zeroed. ** ** (6) If a master journal file is used, then all writes to the database file ** are synced prior to the master journal being deleted. ** ** Definition: Two databases (or the same database at two points it time) ** are said to be "logically equivalent" if they give the same answer to ** all queries. Note in particular the the content of freelist leaf ** pages can be changed arbitarily without effecting the logical equivalence ** of the database. ** ** (7) At any time, if any subset, including the empty set and the total set, ** of the unsynced changes to a rollback journal are removed and the ** journal is rolled back, the resulting database file will be logical ** equivalent to the database file at the beginning of the transaction. ** ** (8) When a transaction is rolled back, the xTruncate method of the VFS ** is called to restore the database file to the same size it was at ** the beginning of the transaction. (In some VFSes, the xTruncate ** method is a no-op, but that does not change the fact the SQLite will ** invoke it.) ** ** (9) Whenever the database file is modified, at least one bit in the range ** of bytes from 24 through 39 inclusive will be changed prior to releasing ** the EXCLUSIVE lock. ** ** (10) The pattern of bits in bytes 24 through 39 shall not repeat in less ** than one billion transactions. ** ** (11) A database file is well-formed at the beginning and at the conclusion ** of every transaction. ** ** (12) An EXCLUSIVE lock is held on the database file when writing to ** the database file. ** ** (13) A SHARED lock is held on the database file while reading any ** content out of the database file. */ /* ** Macros for troubleshooting. Normally turned off */ #if 0 int sqlite3PagerTrace=1; /* True to enable tracing */ #define sqlite3DebugPrintf printf #define PAGERTRACE(X) if( sqlite3PagerTrace ){ sqlite3DebugPrintf X; } #else #define PAGERTRACE(X) #endif /* ** The following two macros are used within the PAGERTRACE() macros above ** to print out file-descriptors. ** ** PAGERID() takes a pointer to a Pager struct as its argument. The ** associated file-descriptor is returned. FILEHANDLEID() takes an sqlite3_file ** struct as its argument. */ #define PAGERID(p) ((int)(p->fd)) #define FILEHANDLEID(fd) ((int)fd) /* ** The page cache as a whole is always in one of the following ** states: ** ** PAGER_UNLOCK The page cache is not currently reading or ** writing the database file. There is no ** data held in memory. This is the initial ** state. ** ** PAGER_SHARED The page cache is reading the database. ** Writing is not permitted. There can be ** multiple readers accessing the same database ** file at the same time. ** ** PAGER_RESERVED This process has reserved the database for writing ** but has not yet made any changes. Only one process ** at a time can reserve the database. The original ** database file has not been modified so other ** processes may still be reading the on-disk ** database file. ** ** PAGER_EXCLUSIVE The page cache is writing the database. ** Access is exclusive. No other processes or ** threads can be reading or writing while one ** process is writing. ** ** PAGER_SYNCED The pager moves to this state from PAGER_EXCLUSIVE ** after all dirty pages have been written to the ** database file and the file has been synced to ** disk. All that remains to do is to remove or ** truncate the journal file and the transaction ** will be committed. ** ** The page cache comes up in PAGER_UNLOCK. The first time a ** sqlite3PagerGet() occurs, the state transitions to PAGER_SHARED. ** After all pages have been released using sqlite_page_unref(), ** the state transitions back to PAGER_UNLOCK. The first time ** that sqlite3PagerWrite() is called, the state transitions to ** PAGER_RESERVED. (Note that sqlite3PagerWrite() can only be ** called on an outstanding page which means that the pager must ** be in PAGER_SHARED before it transitions to PAGER_RESERVED.) ** PAGER_RESERVED means that there is an open rollback journal. ** The transition to PAGER_EXCLUSIVE occurs before any changes ** are made to the database file, though writes to the rollback ** journal occurs with just PAGER_RESERVED. After an sqlite3PagerRollback() ** or sqlite3PagerCommitPhaseTwo(), the state can go back to PAGER_SHARED, ** or it can stay at PAGER_EXCLUSIVE if we are in exclusive access mode. */ #define PAGER_UNLOCK 0 #define PAGER_SHARED 1 /* same as SHARED_LOCK */ #define PAGER_RESERVED 2 /* same as RESERVED_LOCK */ #define PAGER_EXCLUSIVE 4 /* same as EXCLUSIVE_LOCK */ #define PAGER_SYNCED 5 /* ** A macro used for invoking the codec if there is one */ #ifdef SQLITE_HAS_CODEC # define CODEC1(P,D,N,X,E) \ if( P->xCodec && P->xCodec(P->pCodec,D,N,X)==0 ){ E; } # define CODEC2(P,D,N,X,E,O) \ if( P->xCodec==0 ){ O=(char*)D; }else \ if( (O=(char*)(P->xCodec(P->pCodec,D,N,X)))==0 ){ E; } #else # define CODEC1(P,D,N,X,E) /* NO-OP */ # define CODEC2(P,D,N,X,E,O) O=(char*)D #endif /* ** The maximum allowed sector size. 64KiB. If the xSectorsize() method ** returns a value larger than this, then MAX_SECTOR_SIZE is used instead. ** This could conceivably cause corruption following a power failure on ** such a system. This is currently an undocumented limit. */ #define MAX_SECTOR_SIZE 0x10000 /* ** An instance of the following structure is allocated for each active ** savepoint and statement transaction in the system. All such structures ** are stored in the Pager.aSavepoint[] array, which is allocated and ** resized using sqlite3Realloc(). ** ** When a savepoint is created, the PagerSavepoint.iHdrOffset field is ** set to 0. If a journal-header is written into the main journal while ** the savepoint is active, then iHdrOffset is set to the byte offset ** immediately following the last journal record written into the main ** journal before the journal-header. This is required during savepoint ** rollback (see pagerPlaybackSavepoint()). */ typedef struct PagerSavepoint PagerSavepoint; struct PagerSavepoint { i64 iOffset; /* Starting offset in main journal */ i64 iHdrOffset; /* See above */ Bitvec *pInSavepoint; /* Set of pages in this savepoint */ Pgno nOrig; /* Original number of pages in file */ Pgno iSubRec; /* Index of first record in sub-journal */ #ifndef SQLITE_OMIT_WAL u32 aWalData[WAL_SAVEPOINT_NDATA]; /* WAL savepoint context */ #endif }; /* ** A open page cache is an instance of the following structure. ** ** errCode ** ** Pager.errCode may be set to SQLITE_IOERR, SQLITE_CORRUPT, or ** or SQLITE_FULL. Once one of the first three errors occurs, it persists ** and is returned as the result of every major pager API call. The ** SQLITE_FULL return code is slightly different. It persists only until the ** next successful rollback is performed on the pager cache. Also, ** SQLITE_FULL does not affect the sqlite3PagerGet() and sqlite3PagerLookup() ** APIs, they may still be used successfully. ** ** dbSizeValid, dbSize, dbOrigSize, dbFileSize ** ** Managing the size of the database file in pages is a little complicated. ** The variable Pager.dbSize contains the number of pages that the database ** image currently contains. As the database image grows or shrinks this ** variable is updated. The variable Pager.dbFileSize contains the number ** of pages in the database file. This may be different from Pager.dbSize ** if some pages have been appended to the database image but not yet written ** out from the cache to the actual file on disk. Or if the image has been ** truncated by an incremental-vacuum operation. The Pager.dbOrigSize variable ** contains the number of pages in the database image when the current ** transaction was opened. The contents of all three of these variables is ** only guaranteed to be correct if the boolean Pager.dbSizeValid is true. ** ** TODO: Under what conditions is dbSizeValid set? Cleared? ** ** changeCountDone ** ** This boolean variable is used to make sure that the change-counter ** (the 4-byte header field at byte offset 24 of the database file) is ** not updated more often than necessary. ** ** It is set to true when the change-counter field is updated, which ** can only happen if an exclusive lock is held on the database file. ** It is cleared (set to false) whenever an exclusive lock is ** relinquished on the database file. Each time a transaction is committed, ** The changeCountDone flag is inspected. If it is true, the work of ** updating the change-counter is omitted for the current transaction. ** ** This mechanism means that when running in exclusive mode, a connection ** need only update the change-counter once, for the first transaction ** committed. ** ** dbModified ** ** The dbModified flag is set whenever a database page is dirtied. ** It is cleared at the end of each transaction. ** ** It is used when committing or otherwise ending a transaction. If ** the dbModified flag is clear then less work has to be done. ** ** journalStarted ** ** This flag is set whenever the the main journal is opened and ** initialized ** ** The point of this flag is that it must be set after the ** first journal header in a journal file has been synced to disk. ** After this has happened, new pages appended to the database ** do not need the PGHDR_NEED_SYNC flag set, as they do not need ** to wait for a journal sync before they can be written out to ** the database file (see function pager_write()). ** ** setMaster ** ** This variable is used to ensure that the master journal file name ** (if any) is only written into the journal file once. ** ** When committing a transaction, the master journal file name (if any) ** may be written into the journal file while the pager is still in ** PAGER_RESERVED state (see CommitPhaseOne() for the action). It ** then attempts to upgrade to an exclusive lock. If this attempt ** fails, then SQLITE_BUSY may be returned to the user and the user ** may attempt to commit the transaction again later (calling ** CommitPhaseOne() again). This flag is used to ensure that the ** master journal name is only written to the journal file the first ** time CommitPhaseOne() is called. ** ** doNotSpill, doNotSyncSpill ** ** When enabled, cache spills are prohibited. The doNotSpill variable ** inhibits all cache spill and doNotSyncSpill inhibits those spills that ** would require a journal sync. The doNotSyncSpill is set and cleared ** by sqlite3PagerWrite() in order to prevent a journal sync from happening ** in between the journalling of two pages on the same sector. The ** doNotSpill value set to prevent pagerStress() from trying to use ** the journal during a rollback. ** ** needSync ** ** TODO: It might be easier to set this variable in writeJournalHdr() ** and writeMasterJournal() only. Change its meaning to "unsynced data ** has been written to the journal". ** ** subjInMemory ** ** This is a boolean variable. If true, then any required sub-journal ** is opened as an in-memory journal file. If false, then in-memory ** sub-journals are only used for in-memory pager files. */ struct Pager { sqlite3_vfs *pVfs; /* OS functions to use for IO */ u8 exclusiveMode; /* Boolean. True if locking_mode==EXCLUSIVE */ u8 journalMode; /* On of the PAGER_JOURNALMODE_* values */ u8 useJournal; /* Use a rollback journal on this file */ u8 noReadlock; /* Do not bother to obtain readlocks */ u8 noSync; /* Do not sync the journal if true */ u8 fullSync; /* Do extra syncs of the journal for robustness */ u8 sync_flags; /* One of SYNC_NORMAL or SYNC_FULL */ u8 tempFile; /* zFilename is a temporary file */ u8 readOnly; /* True for a read-only database */ u8 memDb; /* True to inhibit all file I/O */ /* The following block contains those class members that are dynamically ** modified during normal operations. The other variables in this structure ** are either constant throughout the lifetime of the pager, or else ** used to store configuration parameters that affect the way the pager ** operates. ** ** The 'state' variable is described in more detail along with the ** descriptions of the values it may take - PAGER_UNLOCK etc. Many of the ** other variables in this block are described in the comment directly ** above this class definition. */ u8 state; /* PAGER_UNLOCK, _SHARED, _RESERVED, etc. */ u8 dbModified; /* True if there are any changes to the Db */ u8 needSync; /* True if an fsync() is needed on the journal */ u8 journalStarted; /* True if header of journal is synced */ u8 changeCountDone; /* Set after incrementing the change-counter */ u8 setMaster; /* True if a m-j name has been written to jrnl */ u8 doNotSpill; /* Do not spill the cache when non-zero */ u8 doNotSyncSpill; /* Do not do a spill that requires jrnl sync */ u8 dbSizeValid; /* Set when dbSize is correct */ u8 subjInMemory; /* True to use in-memory sub-journals */ Pgno dbSize; /* Number of pages in the database */ Pgno dbOrigSize; /* dbSize before the current transaction */ Pgno dbFileSize; /* Number of pages in the database file */ int errCode; /* One of several kinds of errors */ int nRec; /* Pages journalled since last j-header written */ u32 cksumInit; /* Quasi-random value added to every checksum */ u32 nSubRec; /* Number of records written to sub-journal */ Bitvec *pInJournal; /* One bit for each page in the database file */ sqlite3_file *fd; /* File descriptor for database */ sqlite3_file *jfd; /* File descriptor for main journal */ sqlite3_file *sjfd; /* File descriptor for sub-journal */ i64 journalOff; /* Current write offset in the journal file */ i64 journalHdr; /* Byte offset to previous journal header */ i64 journalSizeLimit; /* Size limit for persistent journal files */ PagerSavepoint *aSavepoint; /* Array of active savepoints */ int nSavepoint; /* Number of elements in aSavepoint[] */ char dbFileVers[16]; /* Changes whenever database file changes */ u32 sectorSize; /* Assumed sector size during rollback */ u16 nExtra; /* Add this many bytes to each in-memory page */ i16 nReserve; /* Number of unused bytes at end of each page */ u32 vfsFlags; /* Flags for sqlite3_vfs.xOpen() */ int pageSize; /* Number of bytes in a page */ Pgno mxPgno; /* Maximum allowed size of the database */ char *zFilename; /* Name of the database file */ char *zJournal; /* Name of the journal file */ int (*xBusyHandler)(void*); /* Function to call when busy */ void *pBusyHandlerArg; /* Context argument for xBusyHandler */ #ifdef SQLITE_TEST int nHit, nMiss; /* Cache hits and missing */ int nRead, nWrite; /* Database pages read/written */ #endif void (*xReiniter)(DbPage*); /* Call this routine when reloading pages */ #ifdef SQLITE_HAS_CODEC void *(*xCodec)(void*,void*,Pgno,int); /* Routine for en/decoding data */ void (*xCodecSizeChng)(void*,int,int); /* Notify of page size changes */ void (*xCodecFree)(void*); /* Destructor for the codec */ void *pCodec; /* First argument to xCodec... methods */ #endif char *pTmpSpace; /* Pager.pageSize bytes of space for tmp use */ PCache *pPCache; /* Pointer to page cache object */ sqlite3_backup *pBackup; /* Pointer to list of ongoing backup processes */ #ifndef SQLITE_OMIT_WAL Wal *pWal; /* Write-ahead log used by "journal_mode=wal" */ #endif }; /* ** The following global variables hold counters used for ** testing purposes only. These variables do not exist in ** a non-testing build. These variables are not thread-safe. */ #ifdef SQLITE_TEST int sqlite3_pager_readdb_count = 0; /* Number of full pages read from DB */ int sqlite3_pager_writedb_count = 0; /* Number of full pages written to DB */ int sqlite3_pager_writej_count = 0; /* Number of pages written to journal */ # define PAGER_INCR(v) v++ #else # define PAGER_INCR(v) #endif /* ** Journal files begin with the following magic string. The data ** was obtained from /dev/random. It is used only as a sanity check. ** ** Since version 2.8.0, the journal format contains additional sanity ** checking information. If the power fails while the journal is being ** written, semi-random garbage data might appear in the journal ** file after power is restored. If an attempt is then made ** to roll the journal back, the database could be corrupted. The additional ** sanity checking data is an attempt to discover the garbage in the ** journal and ignore it. ** ** The sanity checking information for the new journal format consists ** of a 32-bit checksum on each page of data. The checksum covers both ** the page number and the pPager->pageSize bytes of data for the page. ** This cksum is initialized to a 32-bit random value that appears in the ** journal file right after the header. The random initializer is important, ** because garbage data that appears at the end of a journal is likely ** data that was once in other files that have now been deleted. If the ** garbage data came from an obsolete journal file, the checksums might ** be correct. But by initializing the checksum to random value which ** is different for every journal, we minimize that risk. */ static const unsigned char aJournalMagic[] = { 0xd9, 0xd5, 0x05, 0xf9, 0x20, 0xa1, 0x63, 0xd7, }; /* ** The size of the of each page record in the journal is given by ** the following macro. */ #define JOURNAL_PG_SZ(pPager) ((pPager->pageSize) + 8) /* ** The journal header size for this pager. This is usually the same ** size as a single disk sector. See also setSectorSize(). */ #define JOURNAL_HDR_SZ(pPager) (pPager->sectorSize) /* ** The macro MEMDB is true if we are dealing with an in-memory database. ** We do this as a macro so that if the SQLITE_OMIT_MEMORYDB macro is set, ** the value of MEMDB will be a constant and the compiler will optimize ** out code that would never execute. */ #ifdef SQLITE_OMIT_MEMORYDB # define MEMDB 0 #else # define MEMDB pPager->memDb #endif /* ** The maximum legal page number is (2^31 - 1). */ #define PAGER_MAX_PGNO 2147483647 #ifndef NDEBUG /* ** Usage: ** ** assert( assert_pager_state(pPager) ); */ static int assert_pager_state(Pager *pPager){ /* A temp-file is always in PAGER_EXCLUSIVE or PAGER_SYNCED state. */ assert( pPager->tempFile==0 || pPager->state>=PAGER_EXCLUSIVE ); /* The changeCountDone flag is always set for temp-files */ assert( pPager->tempFile==0 || pPager->changeCountDone ); return 1; } #endif /* ** Return true if it is necessary to write page *pPg into the sub-journal. ** A page needs to be written into the sub-journal if there exists one ** or more open savepoints for which: ** ** * The page-number is less than or equal to PagerSavepoint.nOrig, and ** * The bit corresponding to the page-number is not set in ** PagerSavepoint.pInSavepoint. */ static int subjRequiresPage(PgHdr *pPg){ Pgno pgno = pPg->pgno; Pager *pPager = pPg->pPager; int i; for(i=0; i<pPager->nSavepoint; i++){ PagerSavepoint *p = &pPager->aSavepoint[i]; if( p->nOrig>=pgno && 0==sqlite3BitvecTest(p->pInSavepoint, pgno) ){ return 1; } } return 0; } /* ** Return true if the page is already in the journal file. */ static int pageInJournal(PgHdr *pPg){ return sqlite3BitvecTest(pPg->pPager->pInJournal, pPg->pgno); } /* ** Read a 32-bit integer from the given file descriptor. Store the integer ** that is read in *pRes. Return SQLITE_OK if everything worked, or an ** error code is something goes wrong. ** ** All values are stored on disk as big-endian. */ static int read32bits(sqlite3_file *fd, i64 offset, u32 *pRes){ unsigned char ac[4]; int rc = sqlite3OsRead(fd, ac, sizeof(ac), offset); if( rc==SQLITE_OK ){ *pRes = sqlite3Get4byte(ac); } return rc; } /* ** Write a 32-bit integer into a string buffer in big-endian byte order. */ #define put32bits(A,B) sqlite3Put4byte((u8*)A,B) /* ** Write a 32-bit integer into the given file descriptor. Return SQLITE_OK ** on success or an error code is something goes wrong. */ static int write32bits(sqlite3_file *fd, i64 offset, u32 val){ char ac[4]; put32bits(ac, val); return sqlite3OsWrite(fd, ac, 4, offset); } /* ** The argument to this macro is a file descriptor (type sqlite3_file*). ** Return 0 if it is not open, or non-zero (but not 1) if it is. ** ** This is so that expressions can be written as: ** ** if( isOpen(pPager->jfd) ){ ... ** ** instead of ** ** if( pPager->jfd->pMethods ){ ... */ #define isOpen(pFd) ((pFd)->pMethods) /* ** If file pFd is open, call sqlite3OsUnlock() on it. */ static int osUnlock(sqlite3_file *pFd, int eLock){ if( !isOpen(pFd) ){ return SQLITE_OK; } return sqlite3OsUnlock(pFd, eLock); } /* ** This function determines whether or not the atomic-write optimization ** can be used with this pager. The optimization can be used if: ** ** (a) the value returned by OsDeviceCharacteristics() indicates that ** a database page may be written atomically, and ** (b) the value returned by OsSectorSize() is less than or equal ** to the page size. ** ** The optimization is also always enabled for temporary files. It is ** an error to call this function if pPager is opened on an in-memory ** database. ** ** If the optimization cannot be used, 0 is returned. If it can be used, ** then the value returned is the size of the journal file when it ** contains rollback data for exactly one page. */ #ifdef SQLITE_ENABLE_ATOMIC_WRITE static int jrnlBufferSize(Pager *pPager){ assert( !MEMDB ); if( !pPager->tempFile ){ int dc; /* Device characteristics */ int nSector; /* Sector size */ int szPage; /* Page size */ assert( isOpen(pPager->fd) ); dc = sqlite3OsDeviceCharacteristics(pPager->fd); nSector = pPager->sectorSize; szPage = pPager->pageSize; assert(SQLITE_IOCAP_ATOMIC512==(512>>8)); assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8)); if( 0==(dc&(SQLITE_IOCAP_ATOMIC|(szPage>>8)) || nSector>szPage) ){ return 0; } } return JOURNAL_HDR_SZ(pPager) + JOURNAL_PG_SZ(pPager); } #endif /* ** If SQLITE_CHECK_PAGES is defined then we do some sanity checking ** on the cache using a hash function. This is used for testing ** and debugging only. */ #ifdef SQLITE_CHECK_PAGES /* ** Return a 32-bit hash of the page data for pPage. */ static u32 pager_datahash(int nByte, unsigned char *pData){ u32 hash = 0; int i; for(i=0; i<nByte; i++){ hash = (hash*1039) + pData[i]; } return hash; } static u32 pager_pagehash(PgHdr *pPage){ return pager_datahash(pPage->pPager->pageSize, (unsigned char *)pPage->pData); } static void pager_set_pagehash(PgHdr *pPage){ pPage->pageHash = pager_pagehash(pPage); } /* ** The CHECK_PAGE macro takes a PgHdr* as an argument. If SQLITE_CHECK_PAGES ** is defined, and NDEBUG is not defined, an assert() statement checks ** that the page is either dirty or still matches the calculated page-hash. */ #define CHECK_PAGE(x) checkPage(x) static void checkPage(PgHdr *pPg){ Pager *pPager = pPg->pPager; assert( !pPg->pageHash || pPager->errCode || (pPg->flags&PGHDR_DIRTY) || pPg->pageHash==pager_pagehash(pPg) ); } #else #define pager_datahash(X,Y) 0 #define pager_pagehash(X) 0 #define CHECK_PAGE(x) #endif /* SQLITE_CHECK_PAGES */ /* ** When this is called the journal file for pager pPager must be open. ** This function attempts to read a master journal file name from the ** end of the file and, if successful, copies it into memory supplied ** by the caller. See comments above writeMasterJournal() for the format ** used to store a master journal file name at the end of a journal file. ** ** zMaster must point to a buffer of at least nMaster bytes allocated by ** the caller. This should be sqlite3_vfs.mxPathname+1 (to ensure there is ** enough space to write the master journal name). If the master journal ** name in the journal is longer than nMaster bytes (including a ** nul-terminator), then this is handled as if no master journal name ** were present in the journal. ** ** If a master journal file name is present at the end of the journal ** file, then it is copied into the buffer pointed to by zMaster. A ** nul-terminator byte is appended to the buffer following the master ** journal file name. ** ** If it is determined that no master journal file name is present ** zMaster[0] is set to 0 and SQLITE_OK returned. ** ** If an error occurs while reading from the journal file, an SQLite ** error code is returned. */ static int readMasterJournal(sqlite3_file *pJrnl, char *zMaster, u32 nMaster){ int rc; /* Return code */ u32 len; /* Length in bytes of master journal name */ i64 szJ; /* Total size in bytes of journal file pJrnl */ u32 cksum; /* MJ checksum value read from journal */ u32 u; /* Unsigned loop counter */ unsigned char aMagic[8]; /* A buffer to hold the magic header */ zMaster[0] = '\0'; if( SQLITE_OK!=(rc = sqlite3OsFileSize(pJrnl, &szJ)) || szJ<16 || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-16, &len)) || len>=nMaster || SQLITE_OK!=(rc = read32bits(pJrnl, szJ-12, &cksum)) || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, aMagic, 8, szJ-8)) || memcmp(aMagic, aJournalMagic, 8) || SQLITE_OK!=(rc = sqlite3OsRead(pJrnl, zMaster, len, szJ-16-len)) ){ return rc; } /* See if the checksum matches the master journal name */ for(u=0; u<len; u++){ cksum -= zMaster[u]; } if( cksum ){ /* If the checksum doesn't add up, then one or more of the disk sectors ** containing the master journal filename is corrupted. This means ** definitely roll back, so just return SQLITE_OK and report a (nul) ** master-journal filename. */ len = 0; } zMaster[len] = '\0'; return SQLITE_OK; } /* ** Return the offset of the sector boundary at or immediately ** following the value in pPager->journalOff, assuming a sector ** size of pPager->sectorSize bytes. ** ** i.e for a sector size of 512: ** ** Pager.journalOff Return value ** --------------------------------------- ** 0 0 ** 512 512 ** 100 512 ** 2000 2048 ** */ static i64 journalHdrOffset(Pager *pPager){ i64 offset = 0; i64 c = pPager->journalOff; if( c ){ offset = ((c-1)/JOURNAL_HDR_SZ(pPager) + 1) * JOURNAL_HDR_SZ(pPager); } assert( offset%JOURNAL_HDR_SZ(pPager)==0 ); assert( offset>=c ); assert( (offset-c)<JOURNAL_HDR_SZ(pPager) ); return offset; } /* ** The journal file must be open when this function is called. ** ** This function is a no-op if the journal file has not been written to ** within the current transaction (i.e. if Pager.journalOff==0). ** ** If doTruncate is non-zero or the Pager.journalSizeLimit variable is ** set to 0, then truncate the journal file to zero bytes in size. Otherwise, ** zero the 28-byte header at the start of the journal file. In either case, ** if the pager is not in no-sync mode, sync the journal file immediately ** after writing or truncating it. ** ** If Pager.journalSizeLimit is set to a positive, non-zero value, and ** following the truncation or zeroing described above the size of the ** journal file in bytes is larger than this value, then truncate the ** journal file to Pager.journalSizeLimit bytes. The journal file does ** not need to be synced following this operation. ** ** If an IO error occurs, abandon processing and return the IO error code. ** Otherwise, return SQLITE_OK. */ static int zeroJournalHdr(Pager *pPager, int doTruncate){ int rc = SQLITE_OK; /* Return code */ assert( isOpen(pPager->jfd) ); if( pPager->journalOff ){ const i64 iLimit = pPager->journalSizeLimit; /* Local cache of jsl */ IOTRACE(("JZEROHDR %p\n", pPager)) if( doTruncate || iLimit==0 ){ rc = sqlite3OsTruncate(pPager->jfd, 0); }else{ static const char zeroHdr[28] = {0}; rc = sqlite3OsWrite(pPager->jfd, zeroHdr, sizeof(zeroHdr), 0); } if( rc==SQLITE_OK && !pPager->noSync ){ rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_DATAONLY|pPager->sync_flags); } /* At this point the transaction is committed but the write lock ** is still held on the file. If there is a size limit configured for ** the persistent journal and the journal file currently consumes more ** space than that limit allows for, truncate it now. There is no need ** to sync the file following this operation. */ if( rc==SQLITE_OK && iLimit>0 ){ i64 sz; rc = sqlite3OsFileSize(pPager->jfd, &sz); if( rc==SQLITE_OK && sz>iLimit ){ rc = sqlite3OsTruncate(pPager->jfd, iLimit); } } } return rc; } /* ** The journal file must be open when this routine is called. A journal ** header (JOURNAL_HDR_SZ bytes) is written into the journal file at the ** current location. ** ** The format for the journal header is as follows: ** - 8 bytes: Magic identifying journal format. ** - 4 bytes: Number of records in journal, or -1 no-sync mode is on. ** - 4 bytes: Random number used for page hash. ** - 4 bytes: Initial database page count. ** - 4 bytes: Sector size used by the process that wrote this journal. ** - 4 bytes: Database page size. ** ** Followed by (JOURNAL_HDR_SZ - 28) bytes of unused space. */ static int writeJournalHdr(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ char *zHeader = pPager->pTmpSpace; /* Temporary space used to build header */ u32 nHeader = pPager->pageSize; /* Size of buffer pointed to by zHeader */ u32 nWrite; /* Bytes of header sector written */ int ii; /* Loop counter */ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */ if( nHeader>JOURNAL_HDR_SZ(pPager) ){ nHeader = JOURNAL_HDR_SZ(pPager); } /* If there are active savepoints and any of them were created ** since the most recent journal header was written, update the ** PagerSavepoint.iHdrOffset fields now. */ for(ii=0; ii<pPager->nSavepoint; ii++){ if( pPager->aSavepoint[ii].iHdrOffset==0 ){ pPager->aSavepoint[ii].iHdrOffset = pPager->journalOff; } } pPager->journalHdr = pPager->journalOff = journalHdrOffset(pPager); /* ** Write the nRec Field - the number of page records that follow this ** journal header. Normally, zero is written to this value at this time. ** After the records are added to the journal (and the journal synced, ** if in full-sync mode), the zero is overwritten with the true number ** of records (see syncJournal()). ** ** A faster alternative is to write 0xFFFFFFFF to the nRec field. When ** reading the journal this value tells SQLite to assume that the ** rest of the journal file contains valid page records. This assumption ** is dangerous, as if a failure occurred whilst writing to the journal ** file it may contain some garbage data. There are two scenarios ** where this risk can be ignored: ** ** * When the pager is in no-sync mode. Corruption can follow a ** power failure in this case anyway. ** ** * When the SQLITE_IOCAP_SAFE_APPEND flag is set. This guarantees ** that garbage data is never appended to the journal file. */ assert( isOpen(pPager->fd) || pPager->noSync ); if( (pPager->noSync) || (pPager->journalMode==PAGER_JOURNALMODE_MEMORY) || (sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND) ){ memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic)); put32bits(&zHeader[sizeof(aJournalMagic)], 0xffffffff); }else{ memset(zHeader, 0, sizeof(aJournalMagic)+4); } /* The random check-hash initialiser */ sqlite3_randomness(sizeof(pPager->cksumInit), &pPager->cksumInit); put32bits(&zHeader[sizeof(aJournalMagic)+4], pPager->cksumInit); /* The initial database size */ put32bits(&zHeader[sizeof(aJournalMagic)+8], pPager->dbOrigSize); /* The assumed sector size for this process */ put32bits(&zHeader[sizeof(aJournalMagic)+12], pPager->sectorSize); /* The page size */ put32bits(&zHeader[sizeof(aJournalMagic)+16], pPager->pageSize); /* Initializing the tail of the buffer is not necessary. Everything ** works find if the following memset() is omitted. But initializing ** the memory prevents valgrind from complaining, so we are willing to ** take the performance hit. */ memset(&zHeader[sizeof(aJournalMagic)+20], 0, nHeader-(sizeof(aJournalMagic)+20)); /* In theory, it is only necessary to write the 28 bytes that the ** journal header consumes to the journal file here. Then increment the ** Pager.journalOff variable by JOURNAL_HDR_SZ so that the next ** record is written to the following sector (leaving a gap in the file ** that will be implicitly filled in by the OS). ** ** However it has been discovered that on some systems this pattern can ** be significantly slower than contiguously writing data to the file, ** even if that means explicitly writing data to the block of ** (JOURNAL_HDR_SZ - 28) bytes that will not be used. So that is what ** is done. ** ** The loop is required here in case the sector-size is larger than the ** database page size. Since the zHeader buffer is only Pager.pageSize ** bytes in size, more than one call to sqlite3OsWrite() may be required ** to populate the entire journal header sector. */ for(nWrite=0; rc==SQLITE_OK&&nWrite<JOURNAL_HDR_SZ(pPager); nWrite+=nHeader){ IOTRACE(("JHDR %p %lld %d\n", pPager, pPager->journalHdr, nHeader)) rc = sqlite3OsWrite(pPager->jfd, zHeader, nHeader, pPager->journalOff); assert( pPager->journalHdr <= pPager->journalOff ); pPager->journalOff += nHeader; } return rc; } /* ** The journal file must be open when this is called. A journal header file ** (JOURNAL_HDR_SZ bytes) is read from the current location in the journal ** file. The current location in the journal file is given by ** pPager->journalOff. See comments above function writeJournalHdr() for ** a description of the journal header format. ** ** If the header is read successfully, *pNRec is set to the number of ** page records following this header and *pDbSize is set to the size of the ** database before the transaction began, in pages. Also, pPager->cksumInit ** is set to the value read from the journal header. SQLITE_OK is returned ** in this case. ** ** If the journal header file appears to be corrupted, SQLITE_DONE is ** returned and *pNRec and *PDbSize are undefined. If JOURNAL_HDR_SZ bytes ** cannot be read from the journal file an error code is returned. */ static int readJournalHdr( Pager *pPager, /* Pager object */ int isHot, i64 journalSize, /* Size of the open journal file in bytes */ u32 *pNRec, /* OUT: Value read from the nRec field */ u32 *pDbSize /* OUT: Value of original database size field */ ){ int rc; /* Return code */ unsigned char aMagic[8]; /* A buffer to hold the magic header */ i64 iHdrOff; /* Offset of journal header being read */ assert( isOpen(pPager->jfd) ); /* Journal file must be open. */ /* Advance Pager.journalOff to the start of the next sector. If the ** journal file is too small for there to be a header stored at this ** point, return SQLITE_DONE. */ pPager->journalOff = journalHdrOffset(pPager); if( pPager->journalOff+JOURNAL_HDR_SZ(pPager) > journalSize ){ return SQLITE_DONE; } iHdrOff = pPager->journalOff; /* Read in the first 8 bytes of the journal header. If they do not match ** the magic string found at the start of each journal header, return ** SQLITE_DONE. If an IO error occurs, return an error code. Otherwise, ** proceed. */ if( isHot || iHdrOff!=pPager->journalHdr ){ rc = sqlite3OsRead(pPager->jfd, aMagic, sizeof(aMagic), iHdrOff); if( rc ){ return rc; } if( memcmp(aMagic, aJournalMagic, sizeof(aMagic))!=0 ){ return SQLITE_DONE; } } /* Read the first three 32-bit fields of the journal header: The nRec ** field, the checksum-initializer and the database size at the start ** of the transaction. Return an error code if anything goes wrong. */ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+8, pNRec)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+12, &pPager->cksumInit)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+16, pDbSize)) ){ return rc; } if( pPager->journalOff==0 ){ u32 iPageSize; /* Page-size field of journal header */ u32 iSectorSize; /* Sector-size field of journal header */ u16 iPageSize16; /* Copy of iPageSize in 16-bit variable */ /* Read the page-size and sector-size journal header fields. */ if( SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+20, &iSectorSize)) || SQLITE_OK!=(rc = read32bits(pPager->jfd, iHdrOff+24, &iPageSize)) ){ return rc; } /* Check that the values read from the page-size and sector-size fields ** are within range. To be 'in range', both values need to be a power ** of two greater than or equal to 512 or 32, and not greater than their ** respective compile time maximum limits. */ if( iPageSize<512 || iSectorSize<32 || iPageSize>SQLITE_MAX_PAGE_SIZE || iSectorSize>MAX_SECTOR_SIZE || ((iPageSize-1)&iPageSize)!=0 || ((iSectorSize-1)&iSectorSize)!=0 ){ /* If the either the page-size or sector-size in the journal-header is ** invalid, then the process that wrote the journal-header must have ** crashed before the header was synced. In this case stop reading ** the journal file here. */ return SQLITE_DONE; } /* Update the page-size to match the value read from the journal. ** Use a testcase() macro to make sure that malloc failure within ** PagerSetPagesize() is tested. */ iPageSize16 = (u16)iPageSize; rc = sqlite3PagerSetPagesize(pPager, &iPageSize16, -1); testcase( rc!=SQLITE_OK ); assert( rc!=SQLITE_OK || iPageSize16==(u16)iPageSize ); /* Update the assumed sector-size to match the value used by ** the process that created this journal. If this journal was ** created by a process other than this one, then this routine ** is being called from within pager_playback(). The local value ** of Pager.sectorSize is restored at the end of that routine. */ pPager->sectorSize = iSectorSize; } pPager->journalOff += JOURNAL_HDR_SZ(pPager); return rc; } /* ** Write the supplied master journal name into the journal file for pager ** pPager at the current location. The master journal name must be the last ** thing written to a journal file. If the pager is in full-sync mode, the ** journal file descriptor is advanced to the next sector boundary before ** anything is written. The format is: ** ** + 4 bytes: PAGER_MJ_PGNO. ** + N bytes: Master journal filename in utf-8. ** + 4 bytes: N (length of master journal name in bytes, no nul-terminator). ** + 4 bytes: Master journal name checksum. ** + 8 bytes: aJournalMagic[]. ** ** The master journal page checksum is the sum of the bytes in the master ** journal name, where each byte is interpreted as a signed 8-bit integer. ** ** If zMaster is a NULL pointer (occurs for a single database transaction), ** this call is a no-op. */ static int writeMasterJournal(Pager *pPager, const char *zMaster){ int rc; /* Return code */ int nMaster; /* Length of string zMaster */ i64 iHdrOff; /* Offset of header in journal file */ i64 jrnlSize; /* Size of journal file on disk */ u32 cksum = 0; /* Checksum of string zMaster */ if( !zMaster || pPager->setMaster || pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->journalMode==PAGER_JOURNALMODE_OFF ){ return SQLITE_OK; } pPager->setMaster = 1; assert( isOpen(pPager->jfd) ); assert( pPager->journalHdr <= pPager->journalOff ); /* Calculate the length in bytes and the checksum of zMaster */ for(nMaster=0; zMaster[nMaster]; nMaster++){ cksum += zMaster[nMaster]; } /* If in full-sync mode, advance to the next disk sector before writing ** the master journal name. This is in case the previous page written to ** the journal has already been synced. */ if( pPager->fullSync ){ pPager->journalOff = journalHdrOffset(pPager); } iHdrOff = pPager->journalOff; /* Write the master journal data to the end of the journal file. If ** an error occurs, return the error code to the caller. */ if( (0 != (rc = write32bits(pPager->jfd, iHdrOff, PAGER_MJ_PGNO(pPager)))) || (0 != (rc = sqlite3OsWrite(pPager->jfd, zMaster, nMaster, iHdrOff+4))) || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster, nMaster))) || (0 != (rc = write32bits(pPager->jfd, iHdrOff+4+nMaster+4, cksum))) || (0 != (rc = sqlite3OsWrite(pPager->jfd, aJournalMagic, 8, iHdrOff+4+nMaster+8))) ){ return rc; } pPager->journalOff += (nMaster+20); pPager->needSync = !pPager->noSync; /* If the pager is in peristent-journal mode, then the physical ** journal-file may extend past the end of the master-journal name ** and 8 bytes of magic data just written to the file. This is ** dangerous because the code to rollback a hot-journal file ** will not be able to find the master-journal name to determine ** whether or not the journal is hot. ** ** Easiest thing to do in this scenario is to truncate the journal ** file to the required size. */ if( SQLITE_OK==(rc = sqlite3OsFileSize(pPager->jfd, &jrnlSize)) && jrnlSize>pPager->journalOff ){ rc = sqlite3OsTruncate(pPager->jfd, pPager->journalOff); } return rc; } /* ** Find a page in the hash table given its page number. Return ** a pointer to the page or NULL if the requested page is not ** already in memory. */ static PgHdr *pager_lookup(Pager *pPager, Pgno pgno){ PgHdr *p; /* Return value */ /* It is not possible for a call to PcacheFetch() with createFlag==0 to ** fail, since no attempt to allocate dynamic memory will be made. */ (void)sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &p); return p; } /* ** Unless the pager is in error-state, discard all in-memory pages. If ** the pager is in error-state, then this call is a no-op. ** ** TODO: Why can we not reset the pager while in error state? */ static void pager_reset(Pager *pPager){ if( SQLITE_OK==pPager->errCode ){ sqlite3BackupRestart(pPager->pBackup); sqlite3PcacheClear(pPager->pPCache); pPager->dbSizeValid = 0; } } /* ** Free all structures in the Pager.aSavepoint[] array and set both ** Pager.aSavepoint and Pager.nSavepoint to zero. Close the sub-journal ** if it is open and the pager is not in exclusive mode. */ static void releaseAllSavepoints(Pager *pPager){ int ii; /* Iterator for looping through Pager.aSavepoint */ for(ii=0; ii<pPager->nSavepoint; ii++){ sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint); } if( !pPager->exclusiveMode || sqlite3IsMemJournal(pPager->sjfd) ){ sqlite3OsClose(pPager->sjfd); } sqlite3_free(pPager->aSavepoint); pPager->aSavepoint = 0; pPager->nSavepoint = 0; pPager->nSubRec = 0; } /* ** Set the bit number pgno in the PagerSavepoint.pInSavepoint ** bitvecs of all open savepoints. Return SQLITE_OK if successful ** or SQLITE_NOMEM if a malloc failure occurs. */ static int addToSavepointBitvecs(Pager *pPager, Pgno pgno){ int ii; /* Loop counter */ int rc = SQLITE_OK; /* Result code */ for(ii=0; ii<pPager->nSavepoint; ii++){ PagerSavepoint *p = &pPager->aSavepoint[ii]; if( pgno<=p->nOrig ){ rc |= sqlite3BitvecSet(p->pInSavepoint, pgno); testcase( rc==SQLITE_NOMEM ); assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); } } return rc; } /* ** Return true if this pager uses a write-ahead log instead of the usual ** rollback journal. Otherwise false. */ #ifndef SQLITE_OMIT_WAL static int pagerUseWal(Pager *pPager){ return (pPager->pWal!=0); } #else # define pagerUseWal(x) 0 # define pagerRollbackWal(x) 0 # define pagerWalFrames(v,w,x,y,z) 0 # define pagerOpenWalIfPresent(z) SQLITE_OK # define pagerBeginReadTransaction(z) SQLITE_OK #endif /* ** Unlock the database file. This function is a no-op if the pager ** is in exclusive mode. ** ** If the pager is currently in error state, discard the contents of ** the cache and reset the Pager structure internal state. If there is ** an open journal-file, then the next time a shared-lock is obtained ** on the pager file (by this or any other process), it will be ** treated as a hot-journal and rolled back. */ static void pager_unlock(Pager *pPager){ if( !pPager->exclusiveMode ){ int rc = SQLITE_OK; /* Return code */ int iDc = isOpen(pPager->fd)?sqlite3OsDeviceCharacteristics(pPager->fd):0; /* If the operating system support deletion of open files, then ** close the journal file when dropping the database lock. Otherwise ** another connection with journal_mode=delete might delete the file ** out from under us. */ assert( (PAGER_JOURNALMODE_MEMORY & 5)!=1 ); assert( (PAGER_JOURNALMODE_OFF & 5)!=1 ); assert( (PAGER_JOURNALMODE_WAL & 5)!=1 ); assert( (PAGER_JOURNALMODE_DELETE & 5)!=1 ); assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 ); assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 ); if( 0==(iDc & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN) || 1!=(pPager->journalMode & 5) ){ sqlite3OsClose(pPager->jfd); } sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; releaseAllSavepoints(pPager); /* If the file is unlocked, somebody else might change it. The ** values stored in Pager.dbSize etc. might become invalid if ** this happens. One can argue that this doesn't need to be cleared ** until the change-counter check fails in PagerSharedLock(). ** Clearing the page size cache here is being conservative. */ pPager->dbSizeValid = 0; if( pagerUseWal(pPager) ){ sqlite3WalEndReadTransaction(pPager->pWal); }else{ rc = osUnlock(pPager->fd, NO_LOCK); } if( rc ){ pPager->errCode = rc; } IOTRACE(("UNLOCK %p\n", pPager)) /* If Pager.errCode is set, the contents of the pager cache cannot be ** trusted. Now that the pager file is unlocked, the contents of the ** cache can be discarded and the error code safely cleared. */ if( pPager->errCode ){ if( rc==SQLITE_OK ){ pPager->errCode = SQLITE_OK; } pager_reset(pPager); } pPager->changeCountDone = 0; pPager->state = PAGER_UNLOCK; pPager->dbModified = 0; } } /* ** This function should be called when an IOERR, CORRUPT or FULL error ** may have occurred. The first argument is a pointer to the pager ** structure, the second the error-code about to be returned by a pager ** API function. The value returned is a copy of the second argument ** to this function. ** ** If the second argument is SQLITE_IOERR, SQLITE_CORRUPT, or SQLITE_FULL ** the error becomes persistent. Until the persistent error is cleared, ** subsequent API calls on this Pager will immediately return the same ** error code. ** ** A persistent error indicates that the contents of the pager-cache ** cannot be trusted. This state can be cleared by completely discarding ** the contents of the pager-cache. If a transaction was active when ** the persistent error occurred, then the rollback journal may need ** to be replayed to restore the contents of the database file (as if ** it were a hot-journal). */ static int pager_error(Pager *pPager, int rc){ int rc2 = rc & 0xff; assert( rc==SQLITE_OK || !MEMDB ); assert( pPager->errCode==SQLITE_FULL || pPager->errCode==SQLITE_OK || (pPager->errCode & 0xff)==SQLITE_IOERR ); if( rc2==SQLITE_FULL || rc2==SQLITE_IOERR ){ pPager->errCode = rc; } return rc; } /* ** Execute a rollback if a transaction is active and unlock the ** database file. ** ** If the pager has already entered the error state, do not attempt ** the rollback at this time. Instead, pager_unlock() is called. The ** call to pager_unlock() will discard all in-memory pages, unlock ** the database file and clear the error state. If this means that ** there is a hot-journal left in the file-system, the next connection ** to obtain a shared lock on the pager (which may be this one) will ** roll it back. ** ** If the pager has not already entered the error state, but an IO or ** malloc error occurs during a rollback, then this will itself cause ** the pager to enter the error state. Which will be cleared by the ** call to pager_unlock(), as described above. */ static void pagerUnlockAndRollback(Pager *pPager){ if( pPager->errCode==SQLITE_OK && pPager->state>=PAGER_RESERVED ){ sqlite3BeginBenignMalloc(); sqlite3PagerRollback(pPager); sqlite3EndBenignMalloc(); } pager_unlock(pPager); } /* ** This routine ends a transaction. A transaction is usually ended by ** either a COMMIT or a ROLLBACK operation. This routine may be called ** after rollback of a hot-journal, or if an error occurs while opening ** the journal file or writing the very first journal-header of a ** database transaction. ** ** If the pager is in PAGER_SHARED or PAGER_UNLOCK state when this ** routine is called, it is a no-op (returns SQLITE_OK). ** ** Otherwise, any active savepoints are released. ** ** If the journal file is open, then it is "finalized". Once a journal ** file has been finalized it is not possible to use it to roll back a ** transaction. Nor will it be considered to be a hot-journal by this ** or any other database connection. Exactly how a journal is finalized ** depends on whether or not the pager is running in exclusive mode and ** the current journal-mode (Pager.journalMode value), as follows: ** ** journalMode==MEMORY ** Journal file descriptor is simply closed. This destroys an ** in-memory journal. ** ** journalMode==TRUNCATE ** Journal file is truncated to zero bytes in size. ** ** journalMode==PERSIST ** The first 28 bytes of the journal file are zeroed. This invalidates ** the first journal header in the file, and hence the entire journal ** file. An invalid journal file cannot be rolled back. ** ** journalMode==DELETE ** The journal file is closed and deleted using sqlite3OsDelete(). ** ** If the pager is running in exclusive mode, this method of finalizing ** the journal file is never used. Instead, if the journalMode is ** DELETE and the pager is in exclusive mode, the method described under ** journalMode==PERSIST is used instead. ** ** After the journal is finalized, if running in non-exclusive mode, the ** pager moves to PAGER_SHARED state (and downgrades the lock on the ** database file accordingly). ** ** If the pager is running in exclusive mode and is in PAGER_SYNCED state, ** it moves to PAGER_EXCLUSIVE. No locks are downgraded when running in ** exclusive mode. ** ** SQLITE_OK is returned if no error occurs. If an error occurs during ** any of the IO operations to finalize the journal file or unlock the ** database then the IO error code is returned to the user. If the ** operation to finalize the journal file fails, then the code still ** tries to unlock the database file if not in exclusive mode. If the ** unlock operation fails as well, then the first error code related ** to the first error encountered (the journal finalization one) is ** returned. */ static int pager_end_transaction(Pager *pPager, int hasMaster){ int rc = SQLITE_OK; /* Error code from journal finalization operation */ int rc2 = SQLITE_OK; /* Error code from db file unlock operation */ if( pPager->state<PAGER_RESERVED ){ return SQLITE_OK; } releaseAllSavepoints(pPager); assert( isOpen(pPager->jfd) || pPager->pInJournal==0 ); if( isOpen(pPager->jfd) ){ assert( !pagerUseWal(pPager) ); /* Finalize the journal file. */ if( sqlite3IsMemJournal(pPager->jfd) ){ assert( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ); sqlite3OsClose(pPager->jfd); }else if( pPager->journalMode==PAGER_JOURNALMODE_TRUNCATE ){ if( pPager->journalOff==0 ){ rc = SQLITE_OK; }else{ rc = sqlite3OsTruncate(pPager->jfd, 0); } pPager->journalOff = 0; pPager->journalStarted = 0; }else if( pPager->journalMode==PAGER_JOURNALMODE_PERSIST || (pPager->exclusiveMode && pPager->journalMode!=PAGER_JOURNALMODE_WAL) ){ rc = zeroJournalHdr(pPager, hasMaster); pager_error(pPager, rc); pPager->journalOff = 0; pPager->journalStarted = 0; }else{ /* This branch may be executed with Pager.journalMode==MEMORY if ** a hot-journal was just rolled back. In this case the journal ** file should be closed and deleted. If this connection writes to ** the database file, it will do so using an in-memory journal. */ assert( pPager->journalMode==PAGER_JOURNALMODE_DELETE || pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->journalMode==PAGER_JOURNALMODE_WAL ); sqlite3OsClose(pPager->jfd); if( !pPager->tempFile ){ rc = sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0); } } #ifdef SQLITE_CHECK_PAGES sqlite3PcacheIterateDirty(pPager->pPCache, pager_set_pagehash); #endif } sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; pPager->nRec = 0; sqlite3PcacheCleanAll(pPager->pPCache); if( pagerUseWal(pPager) ){ rc2 = sqlite3WalEndWriteTransaction(pPager->pWal); assert( rc2==SQLITE_OK ); pPager->state = PAGER_SHARED; /* If the connection was in locking_mode=exclusive mode but is no longer, ** drop the EXCLUSIVE lock held on the database file. */ if( !pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, 0) ){ rc2 = osUnlock(pPager->fd, SHARED_LOCK); } }else if( !pPager->exclusiveMode ){ rc2 = osUnlock(pPager->fd, SHARED_LOCK); pPager->state = PAGER_SHARED; pPager->changeCountDone = 0; }else if( pPager->state==PAGER_SYNCED ){ pPager->state = PAGER_EXCLUSIVE; } pPager->setMaster = 0; pPager->needSync = 0; pPager->dbModified = 0; /* TODO: Is this optimal? Why is the db size invalidated here ** when the database file is not unlocked? */ pPager->dbOrigSize = 0; sqlite3PcacheTruncate(pPager->pPCache, pPager->dbSize); if( !MEMDB ){ pPager->dbSizeValid = 0; } return (rc==SQLITE_OK?rc2:rc); } /* ** Parameter aData must point to a buffer of pPager->pageSize bytes ** of data. Compute and return a checksum based ont the contents of the ** page of data and the current value of pPager->cksumInit. ** ** This is not a real checksum. It is really just the sum of the ** random initial value (pPager->cksumInit) and every 200th byte ** of the page data, starting with byte offset (pPager->pageSize%200). ** Each byte is interpreted as an 8-bit unsigned integer. ** ** Changing the formula used to compute this checksum results in an ** incompatible journal file format. ** ** If journal corruption occurs due to a power failure, the most likely ** scenario is that one end or the other of the record will be changed. ** It is much less likely that the two ends of the journal record will be ** correct and the middle be corrupt. Thus, this "checksum" scheme, ** though fast and simple, catches the mostly likely kind of corruption. */ static u32 pager_cksum(Pager *pPager, const u8 *aData){ u32 cksum = pPager->cksumInit; /* Checksum value to return */ int i = pPager->pageSize-200; /* Loop counter */ while( i>0 ){ cksum += aData[i]; i -= 200; } return cksum; } /* ** Read a single page from either the journal file (if isMainJrnl==1) or ** from the sub-journal (if isMainJrnl==0) and playback that page. ** The page begins at offset *pOffset into the file. The *pOffset ** value is increased to the start of the next page in the journal. ** ** The isMainJrnl flag is true if this is the main rollback journal and ** false for the statement journal. The main rollback journal uses ** checksums - the statement journal does not. ** ** If the page number of the page record read from the (sub-)journal file ** is greater than the current value of Pager.dbSize, then playback is ** skipped and SQLITE_OK is returned. ** ** If pDone is not NULL, then it is a record of pages that have already ** been played back. If the page at *pOffset has already been played back ** (if the corresponding pDone bit is set) then skip the playback. ** Make sure the pDone bit corresponding to the *pOffset page is set ** prior to returning. ** ** If the page record is successfully read from the (sub-)journal file ** and played back, then SQLITE_OK is returned. If an IO error occurs ** while reading the record from the (sub-)journal file or while writing ** to the database file, then the IO error code is returned. If data ** is successfully read from the (sub-)journal file but appears to be ** corrupted, SQLITE_DONE is returned. Data is considered corrupted in ** two circumstances: ** ** * If the record page-number is illegal (0 or PAGER_MJ_PGNO), or ** * If the record is being rolled back from the main journal file ** and the checksum field does not match the record content. ** ** Neither of these two scenarios are possible during a savepoint rollback. ** ** If this is a savepoint rollback, then memory may have to be dynamically ** allocated by this function. If this is the case and an allocation fails, ** SQLITE_NOMEM is returned. */ static int pager_playback_one_page( Pager *pPager, /* The pager being played back */ i64 *pOffset, /* Offset of record to playback */ Bitvec *pDone, /* Bitvec of pages already played back */ int isMainJrnl, /* 1 -> main journal. 0 -> sub-journal. */ int isSavepnt /* True for a savepoint rollback */ ){ int rc; PgHdr *pPg; /* An existing page in the cache */ Pgno pgno; /* The page number of a page in journal */ u32 cksum; /* Checksum used for sanity checking */ char *aData; /* Temporary storage for the page */ sqlite3_file *jfd; /* The file descriptor for the journal file */ int isSynced; /* True if journal page is synced */ assert( (isMainJrnl&~1)==0 ); /* isMainJrnl is 0 or 1 */ assert( (isSavepnt&~1)==0 ); /* isSavepnt is 0 or 1 */ assert( isMainJrnl || pDone ); /* pDone always used on sub-journals */ assert( isSavepnt || pDone==0 ); /* pDone never used on non-savepoint */ aData = pPager->pTmpSpace; assert( aData ); /* Temp storage must have already been allocated */ assert( pagerUseWal(pPager)==0 || (!isMainJrnl && isSavepnt) ); /* Read the page number and page data from the journal or sub-journal ** file. Return an error code to the caller if an IO error occurs. */ jfd = isMainJrnl ? pPager->jfd : pPager->sjfd; rc = read32bits(jfd, *pOffset, &pgno); if( rc!=SQLITE_OK ) return rc; rc = sqlite3OsRead(jfd, (u8*)aData, pPager->pageSize, (*pOffset)+4); if( rc!=SQLITE_OK ) return rc; *pOffset += pPager->pageSize + 4 + isMainJrnl*4; /* Sanity checking on the page. This is more important that I originally ** thought. If a power failure occurs while the journal is being written, ** it could cause invalid data to be written into the journal. We need to ** detect this invalid data (with high probability) and ignore it. */ if( pgno==0 || pgno==PAGER_MJ_PGNO(pPager) ){ assert( !isSavepnt ); return SQLITE_DONE; } if( pgno>(Pgno)pPager->dbSize || sqlite3BitvecTest(pDone, pgno) ){ return SQLITE_OK; } if( isMainJrnl ){ rc = read32bits(jfd, (*pOffset)-4, &cksum); if( rc ) return rc; if( !isSavepnt && pager_cksum(pPager, (u8*)aData)!=cksum ){ return SQLITE_DONE; } } if( pDone && (rc = sqlite3BitvecSet(pDone, pgno))!=SQLITE_OK ){ return rc; } assert( pPager->state==PAGER_RESERVED || pPager->state>=PAGER_EXCLUSIVE ); /* If the pager is in RESERVED state, then there must be a copy of this ** page in the pager cache. In this case just update the pager cache, ** not the database file. The page is left marked dirty in this case. ** ** An exception to the above rule: If the database is in no-sync mode ** and a page is moved during an incremental vacuum then the page may ** not be in the pager cache. Later: if a malloc() or IO error occurs ** during a Movepage() call, then the page may not be in the cache ** either. So the condition described in the above paragraph is not ** assert()able. ** ** If in EXCLUSIVE state, then we update the pager cache if it exists ** and the main file. The page is then marked not dirty. ** ** Ticket #1171: The statement journal might contain page content that is ** different from the page content at the start of the transaction. ** This occurs when a page is changed prior to the start of a statement ** then changed again within the statement. When rolling back such a ** statement we must not write to the original database unless we know ** for certain that original page contents are synced into the main rollback ** journal. Otherwise, a power loss might leave modified data in the ** database file without an entry in the rollback journal that can ** restore the database to its original form. Two conditions must be ** met before writing to the database files. (1) the database must be ** locked. (2) we know that the original page content is fully synced ** in the main journal either because the page is not in cache or else ** the page is marked as needSync==0. ** ** 2008-04-14: When attempting to vacuum a corrupt database file, it ** is possible to fail a statement on a database that does not yet exist. ** Do not attempt to write if database file has never been opened. */ if( pagerUseWal(pPager) ){ pPg = 0; }else{ pPg = pager_lookup(pPager, pgno); } assert( pPg || !MEMDB ); PAGERTRACE(("PLAYBACK %d page %d hash(%08x) %s\n", PAGERID(pPager), pgno, pager_datahash(pPager->pageSize, (u8*)aData), (isMainJrnl?"main-journal":"sub-journal") )); if( isMainJrnl ){ isSynced = pPager->noSync || (*pOffset <= pPager->journalHdr); }else{ isSynced = (pPg==0 || 0==(pPg->flags & PGHDR_NEED_SYNC)); } if( (pPager->state>=PAGER_EXCLUSIVE) && isOpen(pPager->fd) && isSynced ){ i64 ofst = (pgno-1)*(i64)pPager->pageSize; testcase( !isSavepnt && pPg!=0 && (pPg->flags&PGHDR_NEED_SYNC)!=0 ); assert( !pagerUseWal(pPager) ); rc = sqlite3OsWrite(pPager->fd, (u8*)aData, pPager->pageSize, ofst); if( pgno>pPager->dbFileSize ){ pPager->dbFileSize = pgno; } if( pPager->pBackup ){ CODEC1(pPager, aData, pgno, 3, rc=SQLITE_NOMEM); sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)aData); CODEC2(pPager, aData, pgno, 7, rc=SQLITE_NOMEM, aData); } }else if( !isMainJrnl && pPg==0 ){ /* If this is a rollback of a savepoint and data was not written to ** the database and the page is not in-memory, there is a potential ** problem. When the page is next fetched by the b-tree layer, it ** will be read from the database file, which may or may not be ** current. ** ** There are a couple of different ways this can happen. All are quite ** obscure. When running in synchronous mode, this can only happen ** if the page is on the free-list at the start of the transaction, then ** populated, then moved using sqlite3PagerMovepage(). ** ** The solution is to add an in-memory page to the cache containing ** the data just read from the sub-journal. Mark the page as dirty ** and if the pager requires a journal-sync, then mark the page as ** requiring a journal-sync before it is written. */ assert( isSavepnt ); assert( pPager->doNotSpill==0 ); pPager->doNotSpill++; rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1); assert( pPager->doNotSpill==1 ); pPager->doNotSpill--; if( rc!=SQLITE_OK ) return rc; pPg->flags &= ~PGHDR_NEED_READ; sqlite3PcacheMakeDirty(pPg); } if( pPg ){ /* No page should ever be explicitly rolled back that is in use, except ** for page 1 which is held in use in order to keep the lock on the ** database active. However such a page may be rolled back as a result ** of an internal error resulting in an automatic call to ** sqlite3PagerRollback(). */ void *pData; pData = pPg->pData; memcpy(pData, (u8*)aData, pPager->pageSize); pPager->xReiniter(pPg); if( isMainJrnl && (!isSavepnt || *pOffset<=pPager->journalHdr) ){ /* If the contents of this page were just restored from the main ** journal file, then its content must be as they were when the ** transaction was first opened. In this case we can mark the page ** as clean, since there will be no need to write it out to the ** database. ** ** There is one exception to this rule. If the page is being rolled ** back as part of a savepoint (or statement) rollback from an ** unsynced portion of the main journal file, then it is not safe ** to mark the page as clean. This is because marking the page as ** clean will clear the PGHDR_NEED_SYNC flag. Since the page is ** already in the journal file (recorded in Pager.pInJournal) and ** the PGHDR_NEED_SYNC flag is cleared, if the page is written to ** again within this transaction, it will be marked as dirty but ** the PGHDR_NEED_SYNC flag will not be set. It could then potentially ** be written out into the database file before its journal file ** segment is synced. If a crash occurs during or following this, ** database corruption may ensue. */ assert( !pagerUseWal(pPager) ); sqlite3PcacheMakeClean(pPg); } #ifdef SQLITE_CHECK_PAGES pPg->pageHash = pager_pagehash(pPg); #endif /* If this was page 1, then restore the value of Pager.dbFileVers. ** Do this before any decoding. */ if( pgno==1 ){ memcpy(&pPager->dbFileVers, &((u8*)pData)[24],sizeof(pPager->dbFileVers)); } /* Decode the page just read from disk */ CODEC1(pPager, pData, pPg->pgno, 3, rc=SQLITE_NOMEM); sqlite3PcacheRelease(pPg); } return rc; } /* ** Parameter zMaster is the name of a master journal file. A single journal ** file that referred to the master journal file has just been rolled back. ** This routine checks if it is possible to delete the master journal file, ** and does so if it is. ** ** Argument zMaster may point to Pager.pTmpSpace. So that buffer is not ** available for use within this function. ** ** When a master journal file is created, it is populated with the names ** of all of its child journals, one after another, formatted as utf-8 ** encoded text. The end of each child journal file is marked with a ** nul-terminator byte (0x00). i.e. the entire contents of a master journal ** file for a transaction involving two databases might be: ** ** "/home/bill/a.db-journal\x00/home/bill/b.db-journal\x00" ** ** A master journal file may only be deleted once all of its child ** journals have been rolled back. ** ** This function reads the contents of the master-journal file into ** memory and loops through each of the child journal names. For ** each child journal, it checks if: ** ** * if the child journal exists, and if so ** * if the child journal contains a reference to master journal ** file zMaster ** ** If a child journal can be found that matches both of the criteria ** above, this function returns without doing anything. Otherwise, if ** no such child journal can be found, file zMaster is deleted from ** the file-system using sqlite3OsDelete(). ** ** If an IO error within this function, an error code is returned. This ** function allocates memory by calling sqlite3Malloc(). If an allocation ** fails, SQLITE_NOMEM is returned. Otherwise, if no IO or malloc errors ** occur, SQLITE_OK is returned. ** ** TODO: This function allocates a single block of memory to load ** the entire contents of the master journal file. This could be ** a couple of kilobytes or so - potentially larger than the page ** size. */ static int pager_delmaster(Pager *pPager, const char *zMaster){ sqlite3_vfs *pVfs = pPager->pVfs; int rc; /* Return code */ sqlite3_file *pMaster; /* Malloc'd master-journal file descriptor */ sqlite3_file *pJournal; /* Malloc'd child-journal file descriptor */ char *zMasterJournal = 0; /* Contents of master journal file */ i64 nMasterJournal; /* Size of master journal file */ char *zJournal; /* Pointer to one journal within MJ file */ char *zMasterPtr; /* Space to hold MJ filename from a journal file */ int nMasterPtr; /* Amount of space allocated to zMasterPtr[] */ /* Allocate space for both the pJournal and pMaster file descriptors. ** If successful, open the master journal file for reading. */ pMaster = (sqlite3_file *)sqlite3MallocZero(pVfs->szOsFile * 2); pJournal = (sqlite3_file *)(((u8 *)pMaster) + pVfs->szOsFile); if( !pMaster ){ rc = SQLITE_NOMEM; }else{ const int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MASTER_JOURNAL); rc = sqlite3OsOpen(pVfs, zMaster, pMaster, flags, 0); } if( rc!=SQLITE_OK ) goto delmaster_out; /* Load the entire master journal file into space obtained from ** sqlite3_malloc() and pointed to by zMasterJournal. Also obtain ** sufficient space (in zMasterPtr) to hold the names of master ** journal files extracted from regular rollback-journals. */ rc = sqlite3OsFileSize(pMaster, &nMasterJournal); if( rc!=SQLITE_OK ) goto delmaster_out; nMasterPtr = pVfs->mxPathname+1; zMasterJournal = sqlite3Malloc((int)nMasterJournal + nMasterPtr + 1); if( !zMasterJournal ){ rc = SQLITE_NOMEM; goto delmaster_out; } zMasterPtr = &zMasterJournal[nMasterJournal+1]; rc = sqlite3OsRead(pMaster, zMasterJournal, (int)nMasterJournal, 0); if( rc!=SQLITE_OK ) goto delmaster_out; zMasterJournal[nMasterJournal] = 0; zJournal = zMasterJournal; while( (zJournal-zMasterJournal)<nMasterJournal ){ int exists; rc = sqlite3OsAccess(pVfs, zJournal, SQLITE_ACCESS_EXISTS, &exists); if( rc!=SQLITE_OK ){ goto delmaster_out; } if( exists ){ /* One of the journals pointed to by the master journal exists. ** Open it and check if it points at the master journal. If ** so, return without deleting the master journal file. */ int c; int flags = (SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL); rc = sqlite3OsOpen(pVfs, zJournal, pJournal, flags, 0); if( rc!=SQLITE_OK ){ goto delmaster_out; } rc = readMasterJournal(pJournal, zMasterPtr, nMasterPtr); sqlite3OsClose(pJournal); if( rc!=SQLITE_OK ){ goto delmaster_out; } c = zMasterPtr[0]!=0 && strcmp(zMasterPtr, zMaster)==0; if( c ){ /* We have a match. Do not delete the master journal file. */ goto delmaster_out; } } zJournal += (sqlite3Strlen30(zJournal)+1); } sqlite3OsClose(pMaster); rc = sqlite3OsDelete(pVfs, zMaster, 0); delmaster_out: sqlite3_free(zMasterJournal); if( pMaster ){ sqlite3OsClose(pMaster); assert( !isOpen(pJournal) ); sqlite3_free(pMaster); } return rc; } /* ** This function is used to change the actual size of the database ** file in the file-system. This only happens when committing a transaction, ** or rolling back a transaction (including rolling back a hot-journal). ** ** If the main database file is not open, or an exclusive lock is not ** held, this function is a no-op. Otherwise, the size of the file is ** changed to nPage pages (nPage*pPager->pageSize bytes). If the file ** on disk is currently larger than nPage pages, then use the VFS ** xTruncate() method to truncate it. ** ** Or, it might might be the case that the file on disk is smaller than ** nPage pages. Some operating system implementations can get confused if ** you try to truncate a file to some size that is larger than it ** currently is, so detect this case and write a single zero byte to ** the end of the new file instead. ** ** If successful, return SQLITE_OK. If an IO error occurs while modifying ** the database file, return the error code to the caller. */ static int pager_truncate(Pager *pPager, Pgno nPage){ int rc = SQLITE_OK; if( pPager->state>=PAGER_EXCLUSIVE && isOpen(pPager->fd) ){ i64 currentSize, newSize; /* TODO: Is it safe to use Pager.dbFileSize here? */ rc = sqlite3OsFileSize(pPager->fd, ¤tSize); newSize = pPager->pageSize*(i64)nPage; if( rc==SQLITE_OK && currentSize!=newSize ){ if( currentSize>newSize ){ rc = sqlite3OsTruncate(pPager->fd, newSize); }else{ rc = sqlite3OsWrite(pPager->fd, "", 1, newSize-1); } if( rc==SQLITE_OK ){ pPager->dbFileSize = nPage; } } } return rc; } /* ** Set the value of the Pager.sectorSize variable for the given ** pager based on the value returned by the xSectorSize method ** of the open database file. The sector size will be used used ** to determine the size and alignment of journal header and ** master journal pointers within created journal files. ** ** For temporary files the effective sector size is always 512 bytes. ** ** Otherwise, for non-temporary files, the effective sector size is ** the value returned by the xSectorSize() method rounded up to 32 if ** it is less than 32, or rounded down to MAX_SECTOR_SIZE if it ** is greater than MAX_SECTOR_SIZE. */ static void setSectorSize(Pager *pPager){ assert( isOpen(pPager->fd) || pPager->tempFile ); if( !pPager->tempFile ){ /* Sector size doesn't matter for temporary files. Also, the file ** may not have been opened yet, in which case the OsSectorSize() ** call will segfault. */ pPager->sectorSize = sqlite3OsSectorSize(pPager->fd); } if( pPager->sectorSize<32 ){ pPager->sectorSize = 512; } if( pPager->sectorSize>MAX_SECTOR_SIZE ){ assert( MAX_SECTOR_SIZE>=512 ); pPager->sectorSize = MAX_SECTOR_SIZE; } } /* ** Playback the journal and thus restore the database file to ** the state it was in before we started making changes. ** ** The journal file format is as follows: ** ** (1) 8 byte prefix. A copy of aJournalMagic[]. ** (2) 4 byte big-endian integer which is the number of valid page records ** in the journal. If this value is 0xffffffff, then compute the ** number of page records from the journal size. ** (3) 4 byte big-endian integer which is the initial value for the ** sanity checksum. ** (4) 4 byte integer which is the number of pages to truncate the ** database to during a rollback. ** (5) 4 byte big-endian integer which is the sector size. The header ** is this many bytes in size. ** (6) 4 byte big-endian integer which is the page size. ** (7) zero padding out to the next sector size. ** (8) Zero or more pages instances, each as follows: ** + 4 byte page number. ** + pPager->pageSize bytes of data. ** + 4 byte checksum ** ** When we speak of the journal header, we mean the first 7 items above. ** Each entry in the journal is an instance of the 8th item. ** ** Call the value from the second bullet "nRec". nRec is the number of ** valid page entries in the journal. In most cases, you can compute the ** value of nRec from the size of the journal file. But if a power ** failure occurred while the journal was being written, it could be the ** case that the size of the journal file had already been increased but ** the extra entries had not yet made it safely to disk. In such a case, ** the value of nRec computed from the file size would be too large. For ** that reason, we always use the nRec value in the header. ** ** If the nRec value is 0xffffffff it means that nRec should be computed ** from the file size. This value is used when the user selects the ** no-sync option for the journal. A power failure could lead to corruption ** in this case. But for things like temporary table (which will be ** deleted when the power is restored) we don't care. ** ** If the file opened as the journal file is not a well-formed ** journal file then all pages up to the first corrupted page are rolled ** back (or no pages if the journal header is corrupted). The journal file ** is then deleted and SQLITE_OK returned, just as if no corruption had ** been encountered. ** ** If an I/O or malloc() error occurs, the journal-file is not deleted ** and an error code is returned. ** ** The isHot parameter indicates that we are trying to rollback a journal ** that might be a hot journal. Or, it could be that the journal is ** preserved because of JOURNALMODE_PERSIST or JOURNALMODE_TRUNCATE. ** If the journal really is hot, reset the pager cache prior rolling ** back any content. If the journal is merely persistent, no reset is ** needed. */ static int pager_playback(Pager *pPager, int isHot){ sqlite3_vfs *pVfs = pPager->pVfs; i64 szJ; /* Size of the journal file in bytes */ u32 nRec; /* Number of Records in the journal */ u32 u; /* Unsigned loop counter */ Pgno mxPg = 0; /* Size of the original file in pages */ int rc; /* Result code of a subroutine */ int res = 1; /* Value returned by sqlite3OsAccess() */ char *zMaster = 0; /* Name of master journal file if any */ int needPagerReset; /* True to reset page prior to first page rollback */ /* Figure out how many records are in the journal. Abort early if ** the journal is empty. */ assert( isOpen(pPager->jfd) ); rc = sqlite3OsFileSize(pPager->jfd, &szJ); if( rc!=SQLITE_OK || szJ==0 ){ goto end_playback; } /* Read the master journal name from the journal, if it is present. ** If a master journal file name is specified, but the file is not ** present on disk, then the journal is not hot and does not need to be ** played back. ** ** TODO: Technically the following is an error because it assumes that ** buffer Pager.pTmpSpace is (mxPathname+1) bytes or larger. i.e. that ** (pPager->pageSize >= pPager->pVfs->mxPathname+1). Using os_unix.c, ** mxPathname is 512, which is the same as the minimum allowable value ** for pageSize. */ zMaster = pPager->pTmpSpace; rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1); if( rc==SQLITE_OK && zMaster[0] ){ rc = sqlite3OsAccess(pVfs, zMaster, SQLITE_ACCESS_EXISTS, &res); } zMaster = 0; if( rc!=SQLITE_OK || !res ){ goto end_playback; } pPager->journalOff = 0; needPagerReset = isHot; /* This loop terminates either when a readJournalHdr() or ** pager_playback_one_page() call returns SQLITE_DONE or an IO error ** occurs. */ while( 1 ){ /* Read the next journal header from the journal file. If there are ** not enough bytes left in the journal file for a complete header, or ** it is corrupted, then a process must of failed while writing it. ** This indicates nothing more needs to be rolled back. */ rc = readJournalHdr(pPager, isHot, szJ, &nRec, &mxPg); if( rc!=SQLITE_OK ){ if( rc==SQLITE_DONE ){ rc = SQLITE_OK; } goto end_playback; } /* If nRec is 0xffffffff, then this journal was created by a process ** working in no-sync mode. This means that the rest of the journal ** file consists of pages, there are no more journal headers. Compute ** the value of nRec based on this assumption. */ if( nRec==0xffffffff ){ assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ); nRec = (int)((szJ - JOURNAL_HDR_SZ(pPager))/JOURNAL_PG_SZ(pPager)); } /* If nRec is 0 and this rollback is of a transaction created by this ** process and if this is the final header in the journal, then it means ** that this part of the journal was being filled but has not yet been ** synced to disk. Compute the number of pages based on the remaining ** size of the file. ** ** The third term of the test was added to fix ticket #2565. ** When rolling back a hot journal, nRec==0 always means that the next ** chunk of the journal contains zero pages to be rolled back. But ** when doing a ROLLBACK and the nRec==0 chunk is the last chunk in ** the journal, it means that the journal might contain additional ** pages that need to be rolled back and that the number of pages ** should be computed based on the journal file size. */ if( nRec==0 && !isHot && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){ nRec = (int)((szJ - pPager->journalOff) / JOURNAL_PG_SZ(pPager)); } /* If this is the first header read from the journal, truncate the ** database file back to its original size. */ if( pPager->journalOff==JOURNAL_HDR_SZ(pPager) ){ rc = pager_truncate(pPager, mxPg); if( rc!=SQLITE_OK ){ goto end_playback; } pPager->dbSize = mxPg; } /* Copy original pages out of the journal and back into the ** database file and/or page cache. */ for(u=0; u<nRec; u++){ if( needPagerReset ){ pager_reset(pPager); needPagerReset = 0; } rc = pager_playback_one_page(pPager,&pPager->journalOff,0,1,0); if( rc!=SQLITE_OK ){ if( rc==SQLITE_DONE ){ rc = SQLITE_OK; pPager->journalOff = szJ; break; }else if( rc==SQLITE_IOERR_SHORT_READ ){ /* If the journal has been truncated, simply stop reading and ** processing the journal. This might happen if the journal was ** not completely written and synced prior to a crash. In that ** case, the database should have never been written in the ** first place so it is OK to simply abandon the rollback. */ rc = SQLITE_OK; goto end_playback; }else{ /* If we are unable to rollback, quit and return the error ** code. This will cause the pager to enter the error state ** so that no further harm will be done. Perhaps the next ** process to come along will be able to rollback the database. */ goto end_playback; } } } } /*NOTREACHED*/ assert( 0 ); end_playback: /* Following a rollback, the database file should be back in its original ** state prior to the start of the transaction, so invoke the ** SQLITE_FCNTL_DB_UNCHANGED file-control method to disable the ** assertion that the transaction counter was modified. */ assert( pPager->fd->pMethods==0 || sqlite3OsFileControl(pPager->fd,SQLITE_FCNTL_DB_UNCHANGED,0)>=SQLITE_OK ); /* If this playback is happening automatically as a result of an IO or ** malloc error that occurred after the change-counter was updated but ** before the transaction was committed, then the change-counter ** modification may just have been reverted. If this happens in exclusive ** mode, then subsequent transactions performed by the connection will not ** update the change-counter at all. This may lead to cache inconsistency ** problems for other processes at some point in the future. So, just ** in case this has happened, clear the changeCountDone flag now. */ pPager->changeCountDone = pPager->tempFile; if( rc==SQLITE_OK ){ zMaster = pPager->pTmpSpace; rc = readMasterJournal(pPager->jfd, zMaster, pPager->pVfs->mxPathname+1); testcase( rc!=SQLITE_OK ); } if( rc==SQLITE_OK && pPager->noSync==0 && pPager->state>=PAGER_EXCLUSIVE ){ rc = sqlite3OsSync(pPager->fd, pPager->sync_flags); } if( rc==SQLITE_OK && pPager->noSync==0 && pPager->state>=PAGER_EXCLUSIVE ){ rc = sqlite3OsSync(pPager->fd, pPager->sync_flags); } if( rc==SQLITE_OK ){ rc = pager_end_transaction(pPager, zMaster[0]!='\0'); testcase( rc!=SQLITE_OK ); } if( rc==SQLITE_OK && zMaster[0] && res ){ /* If there was a master journal and this routine will return success, ** see if it is possible to delete the master journal. */ rc = pager_delmaster(pPager, zMaster); testcase( rc!=SQLITE_OK ); } /* The Pager.sectorSize variable may have been updated while rolling ** back a journal created by a process with a different sector size ** value. Reset it to the correct value for this process. */ setSectorSize(pPager); return rc; } /* ** Read the content for page pPg out of the database file and into ** pPg->pData. A shared lock or greater must be held on the database ** file before this function is called. ** ** If page 1 is read, then the value of Pager.dbFileVers[] is set to ** the value read from the database file. ** ** If an IO error occurs, then the IO error is returned to the caller. ** Otherwise, SQLITE_OK is returned. */ static int readDbPage(PgHdr *pPg){ Pager *pPager = pPg->pPager; /* Pager object associated with page pPg */ Pgno pgno = pPg->pgno; /* Page number to read */ int rc = SQLITE_OK; /* Return code */ int isInWal = 0; /* True if page is in log file */ int pgsz = pPager->pageSize; /* Number of bytes to read */ assert( pPager->state>=PAGER_SHARED && !MEMDB ); assert( isOpen(pPager->fd) ); if( NEVER(!isOpen(pPager->fd)) ){ assert( pPager->tempFile ); memset(pPg->pData, 0, pPager->pageSize); return SQLITE_OK; } if( pagerUseWal(pPager) ){ /* Try to pull the page from the write-ahead log. */ rc = sqlite3WalRead(pPager->pWal, pgno, &isInWal, pgsz, pPg->pData); } if( rc==SQLITE_OK && !isInWal ){ i64 iOffset = (pgno-1)*(i64)pPager->pageSize; rc = sqlite3OsRead(pPager->fd, pPg->pData, pgsz, iOffset); if( rc==SQLITE_IOERR_SHORT_READ ){ rc = SQLITE_OK; } } if( pgno==1 ){ if( rc ){ /* If the read is unsuccessful, set the dbFileVers[] to something ** that will never be a valid file version. dbFileVers[] is a copy ** of bytes 24..39 of the database. Bytes 28..31 should always be ** zero or the size of the database in page. Bytes 32..35 and 35..39 ** should be page numbers which are never 0xffffffff. So filling ** pPager->dbFileVers[] with all 0xff bytes should suffice. ** ** For an encrypted database, the situation is more complex: bytes ** 24..39 of the database are white noise. But the probability of ** white noising equaling 16 bytes of 0xff is vanishingly small so ** we should still be ok. */ memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers)); }else{ u8 *dbFileVers = &((u8*)pPg->pData)[24]; memcpy(&pPager->dbFileVers, dbFileVers, sizeof(pPager->dbFileVers)); } } CODEC1(pPager, pPg->pData, pgno, 3, rc = SQLITE_NOMEM); PAGER_INCR(sqlite3_pager_readdb_count); PAGER_INCR(pPager->nRead); IOTRACE(("PGIN %p %d\n", pPager, pgno)); PAGERTRACE(("FETCH %d page %d hash(%08x)\n", PAGERID(pPager), pgno, pager_pagehash(pPg))); return rc; } #ifndef SQLITE_OMIT_WAL /* ** This function is invoked once for each page that has already been ** written into the log file when a WAL transaction is rolled back. ** Parameter iPg is the page number of said page. The pCtx argument ** is actually a pointer to the Pager structure. ** ** If page iPg is present in the cache, and has no outstanding references, ** it is discarded. Otherwise, if there are one or more outstanding ** references, the page content is reloaded from the database. If the ** attempt to reload content from the database is required and fails, ** return an SQLite error code. Otherwise, SQLITE_OK. */ static int pagerUndoCallback(void *pCtx, Pgno iPg){ int rc = SQLITE_OK; Pager *pPager = (Pager *)pCtx; PgHdr *pPg; pPg = sqlite3PagerLookup(pPager, iPg); if( pPg ){ if( sqlite3PcachePageRefcount(pPg)==1 ){ sqlite3PcacheDrop(pPg); }else{ rc = readDbPage(pPg); if( rc==SQLITE_OK ){ pPager->xReiniter(pPg); } sqlite3PagerUnref(pPg); } } /* Normally, if a transaction is rolled back, any backup processes are ** updated as data is copied out of the rollback journal and into the ** database. This is not generally possible with a WAL database, as ** rollback involves simply truncating the log file. Therefore, if one ** or more frames have already been written to the log (and therefore ** also copied into the backup databases) as part of this transaction, ** the backups must be restarted. */ sqlite3BackupRestart(pPager->pBackup); return rc; } /* ** This function is called to rollback a transaction on a WAL database. */ static int pagerRollbackWal(Pager *pPager){ int rc; /* Return Code */ PgHdr *pList; /* List of dirty pages to revert */ /* For all pages in the cache that are currently dirty or have already ** been written (but not committed) to the log file, do one of the ** following: ** ** + Discard the cached page (if refcount==0), or ** + Reload page content from the database (if refcount>0). */ pPager->dbSize = pPager->dbOrigSize; rc = sqlite3WalUndo(pPager->pWal, pagerUndoCallback, (void *)pPager); pList = sqlite3PcacheDirtyList(pPager->pPCache); while( pList && rc==SQLITE_OK ){ PgHdr *pNext = pList->pDirty; rc = pagerUndoCallback((void *)pPager, pList->pgno); pList = pNext; } return rc; } /* ** This function is a wrapper around sqlite3WalFrames(). As well as logging ** the contents of the list of pages headed by pList (connected by pDirty), ** this function notifies any active backup processes that the pages have ** changed. */ static int pagerWalFrames( Pager *pPager, /* Pager object */ PgHdr *pList, /* List of frames to log */ Pgno nTruncate, /* Database size after this commit */ int isCommit, /* True if this is a commit */ int sync_flags /* Flags to pass to OsSync() (or 0) */ ){ int rc; /* Return code */ assert( pPager->pWal ); rc = sqlite3WalFrames(pPager->pWal, pPager->pageSize, pList, nTruncate, isCommit, sync_flags ); if( rc==SQLITE_OK && pPager->pBackup ){ PgHdr *p; for(p=pList; p; p=p->pDirty){ sqlite3BackupUpdate(pPager->pBackup, p->pgno, (u8 *)p->pData); } } return rc; } /* ** Begin a read transaction on the WAL. ** ** This routine used to be called "pagerOpenSnapshot()" because it essentially ** makes a snapshot of the database at the current point in time and preserves ** that snapshot for use by the reader in spite of concurrently changes by ** other writers or checkpointers. */ static int pagerBeginReadTransaction(Pager *pPager){ int rc; /* Return code */ int changed = 0; /* True if cache must be reset */ assert( pagerUseWal(pPager) ); /* sqlite3WalEndReadTransaction() was not called for the previous ** transaction in locking_mode=EXCLUSIVE. So call it now. If we ** are in locking_mode=NORMAL and EndRead() was previously called, ** the duplicate call is harmless. */ sqlite3WalEndReadTransaction(pPager->pWal); rc = sqlite3WalBeginReadTransaction(pPager->pWal, &changed); if( rc==SQLITE_OK ){ int dummy; if( changed ){ pager_reset(pPager); assert( pPager->errCode || pPager->dbSizeValid==0 ); } rc = sqlite3PagerPagecount(pPager, &dummy); } pPager->state = PAGER_SHARED; return rc; } /* ** Check for the existence of or delete the *-wal file that corresponds to ** the database opened by pPager. ** ** When pExists!=NULL, set *pExists to 1 if the *-wal file exists, or 0 ** if the *-wal file does not exist. ** ** When pExists==NULL, delete the *-wal file if it exists, or the do ** nothing if the *-wal file does not exist. ** ** Return SQLITE_OK on success. If on an IO or OOM error occurs, return ** an SQLite error code. */ static int pagerCheckForOrDeleteWAL(Pager *pPager, int *pExists){ int rc; /* Return code */ char *zWal; /* Name of the WAL file */ assert( !pPager->tempFile ); zWal = sqlite3_mprintf("%s-wal", pPager->zFilename); if( !zWal ){ rc = SQLITE_NOMEM; }else{ if( pExists ){ rc = sqlite3OsAccess(pPager->pVfs, zWal, SQLITE_ACCESS_EXISTS, pExists); }else{ rc = sqlite3OsDelete(pPager->pVfs, zWal, 0); } sqlite3_free(zWal); } return rc; } /* ** Check if the *-wal file that corresponds to the database opened by pPager ** exists if the database is not empy, or verify that the *-wal file does ** not exist (by deleting it) if the database file is empty. ** ** If the database is not empty and the *-wal file exists, open the pager ** in WAL mode. If the database is empty or if no *-wal file exists and ** if no error occurs, make sure Pager.journalMode is not set to ** PAGER_JOURNALMODE_WAL. ** ** Return SQLITE_OK or an error code. ** ** If the WAL file is opened, also open a snapshot (read transaction). ** ** The caller must hold a SHARED lock on the database file to call this ** function. Because an EXCLUSIVE lock on the db file is required to delete ** a WAL on a none-empty database, this ensures there is no race condition ** between the xAccess() below and an xDelete() being executed by some ** other connection. */ static int pagerOpenWalIfPresent(Pager *pPager){ int rc = SQLITE_OK; if( !pPager->tempFile ){ int isWal; /* True if WAL file exists */ int nPage; /* Size of the database file */ assert( pPager->state>=SHARED_LOCK ); rc = sqlite3PagerPagecount(pPager, &nPage); if( rc ) return rc; if( nPage==0 ){ rc = pagerCheckForOrDeleteWAL(pPager, 0); isWal = 0; }else{ rc = pagerCheckForOrDeleteWAL(pPager, &isWal); } if( rc==SQLITE_OK ){ if( isWal ){ pager_reset(pPager); rc = sqlite3PagerOpenWal(pPager, 0); if( rc==SQLITE_OK ){ rc = pagerBeginReadTransaction(pPager); } }else if( pPager->journalMode==PAGER_JOURNALMODE_WAL ){ pPager->journalMode = PAGER_JOURNALMODE_DELETE; } } } return rc; } #endif /* ** Playback savepoint pSavepoint. Or, if pSavepoint==NULL, then playback ** the entire master journal file. The case pSavepoint==NULL occurs when ** a ROLLBACK TO command is invoked on a SAVEPOINT that is a transaction ** savepoint. ** ** When pSavepoint is not NULL (meaning a non-transaction savepoint is ** being rolled back), then the rollback consists of up to three stages, ** performed in the order specified: ** ** * Pages are played back from the main journal starting at byte ** offset PagerSavepoint.iOffset and continuing to ** PagerSavepoint.iHdrOffset, or to the end of the main journal ** file if PagerSavepoint.iHdrOffset is zero. ** ** * If PagerSavepoint.iHdrOffset is not zero, then pages are played ** back starting from the journal header immediately following ** PagerSavepoint.iHdrOffset to the end of the main journal file. ** ** * Pages are then played back from the sub-journal file, starting ** with the PagerSavepoint.iSubRec and continuing to the end of ** the journal file. ** ** Throughout the rollback process, each time a page is rolled back, the ** corresponding bit is set in a bitvec structure (variable pDone in the ** implementation below). This is used to ensure that a page is only ** rolled back the first time it is encountered in either journal. ** ** If pSavepoint is NULL, then pages are only played back from the main ** journal file. There is no need for a bitvec in this case. ** ** In either case, before playback commences the Pager.dbSize variable ** is reset to the value that it held at the start of the savepoint ** (or transaction). No page with a page-number greater than this value ** is played back. If one is encountered it is simply skipped. */ static int pagerPlaybackSavepoint(Pager *pPager, PagerSavepoint *pSavepoint){ i64 szJ; /* Effective size of the main journal */ i64 iHdrOff; /* End of first segment of main-journal records */ int rc = SQLITE_OK; /* Return code */ Bitvec *pDone = 0; /* Bitvec to ensure pages played back only once */ assert( pPager->state>=PAGER_SHARED ); /* Allocate a bitvec to use to store the set of pages rolled back */ if( pSavepoint ){ pDone = sqlite3BitvecCreate(pSavepoint->nOrig); if( !pDone ){ return SQLITE_NOMEM; } } /* Set the database size back to the value it was before the savepoint ** being reverted was opened. */ pPager->dbSize = pSavepoint ? pSavepoint->nOrig : pPager->dbOrigSize; if( !pSavepoint && pagerUseWal(pPager) ){ return pagerRollbackWal(pPager); } /* Use pPager->journalOff as the effective size of the main rollback ** journal. The actual file might be larger than this in ** PAGER_JOURNALMODE_TRUNCATE or PAGER_JOURNALMODE_PERSIST. But anything ** past pPager->journalOff is off-limits to us. */ szJ = pPager->journalOff; assert( pagerUseWal(pPager)==0 || szJ==0 ); /* Begin by rolling back records from the main journal starting at ** PagerSavepoint.iOffset and continuing to the next journal header. ** There might be records in the main journal that have a page number ** greater than the current database size (pPager->dbSize) but those ** will be skipped automatically. Pages are added to pDone as they ** are played back. */ if( pSavepoint && !pagerUseWal(pPager) ){ iHdrOff = pSavepoint->iHdrOffset ? pSavepoint->iHdrOffset : szJ; pPager->journalOff = pSavepoint->iOffset; while( rc==SQLITE_OK && pPager->journalOff<iHdrOff ){ rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1); } assert( rc!=SQLITE_DONE ); }else{ pPager->journalOff = 0; } /* Continue rolling back records out of the main journal starting at ** the first journal header seen and continuing until the effective end ** of the main journal file. Continue to skip out-of-range pages and ** continue adding pages rolled back to pDone. */ while( rc==SQLITE_OK && pPager->journalOff<szJ ){ u32 ii; /* Loop counter */ u32 nJRec = 0; /* Number of Journal Records */ u32 dummy; rc = readJournalHdr(pPager, 0, szJ, &nJRec, &dummy); assert( rc!=SQLITE_DONE ); /* ** The "pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff" ** test is related to ticket #2565. See the discussion in the ** pager_playback() function for additional information. */ if( nJRec==0 && pPager->journalHdr+JOURNAL_HDR_SZ(pPager)==pPager->journalOff ){ nJRec = (u32)((szJ - pPager->journalOff)/JOURNAL_PG_SZ(pPager)); } for(ii=0; rc==SQLITE_OK && ii<nJRec && pPager->journalOff<szJ; ii++){ rc = pager_playback_one_page(pPager, &pPager->journalOff, pDone, 1, 1); } assert( rc!=SQLITE_DONE ); } assert( rc!=SQLITE_OK || pPager->journalOff>=szJ ); /* Finally, rollback pages from the sub-journal. Page that were ** previously rolled back out of the main journal (and are hence in pDone) ** will be skipped. Out-of-range pages are also skipped. */ if( pSavepoint ){ u32 ii; /* Loop counter */ i64 offset = pSavepoint->iSubRec*(4+pPager->pageSize); if( pagerUseWal(pPager) ){ rc = sqlite3WalSavepointUndo(pPager->pWal, pSavepoint->aWalData); } for(ii=pSavepoint->iSubRec; rc==SQLITE_OK && ii<pPager->nSubRec; ii++){ assert( offset==ii*(4+pPager->pageSize) ); rc = pager_playback_one_page(pPager, &offset, pDone, 0, 1); } assert( rc!=SQLITE_DONE ); } sqlite3BitvecDestroy(pDone); if( rc==SQLITE_OK ){ pPager->journalOff = szJ; } return rc; } /* ** Change the maximum number of in-memory pages that are allowed. */ void sqlite3PagerSetCachesize(Pager *pPager, int mxPage){ sqlite3PcacheSetCachesize(pPager->pPCache, mxPage); } /* ** Adjust the robustness of the database to damage due to OS crashes ** or power failures by changing the number of syncs()s when writing ** the rollback journal. There are three levels: ** ** OFF sqlite3OsSync() is never called. This is the default ** for temporary and transient files. ** ** NORMAL The journal is synced once before writes begin on the ** database. This is normally adequate protection, but ** it is theoretically possible, though very unlikely, ** that an inopertune power failure could leave the journal ** in a state which would cause damage to the database ** when it is rolled back. ** ** FULL The journal is synced twice before writes begin on the ** database (with some additional information - the nRec field ** of the journal header - being written in between the two ** syncs). If we assume that writing a ** single disk sector is atomic, then this mode provides ** assurance that the journal will not be corrupted to the ** point of causing damage to the database during rollback. ** ** Numeric values associated with these states are OFF==1, NORMAL=2, ** and FULL=3. */ #ifndef SQLITE_OMIT_PAGER_PRAGMAS void sqlite3PagerSetSafetyLevel(Pager *pPager, int level, int bFullFsync){ pPager->noSync = (level==1 || pPager->tempFile) ?1:0; pPager->fullSync = (level==3 && !pPager->tempFile) ?1:0; pPager->sync_flags = (bFullFsync?SQLITE_SYNC_FULL:SQLITE_SYNC_NORMAL); if( pPager->noSync ) pPager->needSync = 0; } #endif /* ** The following global variable is incremented whenever the library ** attempts to open a temporary file. This information is used for ** testing and analysis only. */ #ifdef SQLITE_TEST int sqlite3_opentemp_count = 0; #endif /* ** Open a temporary file. ** ** Write the file descriptor into *pFile. Return SQLITE_OK on success ** or some other error code if we fail. The OS will automatically ** delete the temporary file when it is closed. ** ** The flags passed to the VFS layer xOpen() call are those specified ** by parameter vfsFlags ORed with the following: ** ** SQLITE_OPEN_READWRITE ** SQLITE_OPEN_CREATE ** SQLITE_OPEN_EXCLUSIVE ** SQLITE_OPEN_DELETEONCLOSE */ static int pagerOpentemp( Pager *pPager, /* The pager object */ sqlite3_file *pFile, /* Write the file descriptor here */ int vfsFlags /* Flags passed through to the VFS */ ){ int rc; /* Return code */ #ifdef SQLITE_TEST sqlite3_opentemp_count++; /* Used for testing and analysis only */ #endif vfsFlags |= SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_EXCLUSIVE | SQLITE_OPEN_DELETEONCLOSE; rc = sqlite3OsOpen(pPager->pVfs, 0, pFile, vfsFlags, 0); assert( rc!=SQLITE_OK || isOpen(pFile) ); return rc; } /* ** Set the busy handler function. ** ** The pager invokes the busy-handler if sqlite3OsLock() returns ** SQLITE_BUSY when trying to upgrade from no-lock to a SHARED lock, ** or when trying to upgrade from a RESERVED lock to an EXCLUSIVE ** lock. It does *not* invoke the busy handler when upgrading from ** SHARED to RESERVED, or when upgrading from SHARED to EXCLUSIVE ** (which occurs during hot-journal rollback). Summary: ** ** Transition | Invokes xBusyHandler ** -------------------------------------------------------- ** NO_LOCK -> SHARED_LOCK | Yes ** SHARED_LOCK -> RESERVED_LOCK | No ** SHARED_LOCK -> EXCLUSIVE_LOCK | No ** RESERVED_LOCK -> EXCLUSIVE_LOCK | Yes ** ** If the busy-handler callback returns non-zero, the lock is ** retried. If it returns zero, then the SQLITE_BUSY error is ** returned to the caller of the pager API function. */ void sqlite3PagerSetBusyhandler( Pager *pPager, /* Pager object */ int (*xBusyHandler)(void *), /* Pointer to busy-handler function */ void *pBusyHandlerArg /* Argument to pass to xBusyHandler */ ){ pPager->xBusyHandler = xBusyHandler; pPager->pBusyHandlerArg = pBusyHandlerArg; } /* ** Report the current page size and number of reserved bytes back ** to the codec. */ #ifdef SQLITE_HAS_CODEC static void pagerReportSize(Pager *pPager){ if( pPager->xCodecSizeChng ){ pPager->xCodecSizeChng(pPager->pCodec, pPager->pageSize, (int)pPager->nReserve); } } #else # define pagerReportSize(X) /* No-op if we do not support a codec */ #endif /* ** Change the page size used by the Pager object. The new page size ** is passed in *pPageSize. ** ** If the pager is in the error state when this function is called, it ** is a no-op. The value returned is the error state error code (i.e. ** one of SQLITE_IOERR, SQLITE_CORRUPT or SQLITE_FULL). ** ** Otherwise, if all of the following are true: ** ** * the new page size (value of *pPageSize) is valid (a power ** of two between 512 and SQLITE_MAX_PAGE_SIZE, inclusive), and ** ** * there are no outstanding page references, and ** ** * the database is either not an in-memory database or it is ** an in-memory database that currently consists of zero pages. ** ** then the pager object page size is set to *pPageSize. ** ** If the page size is changed, then this function uses sqlite3PagerMalloc() ** to obtain a new Pager.pTmpSpace buffer. If this allocation attempt ** fails, SQLITE_NOMEM is returned and the page size remains unchanged. ** In all other cases, SQLITE_OK is returned. ** ** If the page size is not changed, either because one of the enumerated ** conditions above is not true, the pager was in error state when this ** function was called, or because the memory allocation attempt failed, ** then *pPageSize is set to the old, retained page size before returning. */ int sqlite3PagerSetPagesize(Pager *pPager, u16 *pPageSize, int nReserve){ int rc = pPager->errCode; if( rc==SQLITE_OK ){ u16 pageSize = *pPageSize; assert( pageSize==0 || (pageSize>=512 && pageSize<=SQLITE_MAX_PAGE_SIZE) ); if( (pPager->memDb==0 || pPager->dbSize==0) && sqlite3PcacheRefCount(pPager->pPCache)==0 && pageSize && pageSize!=pPager->pageSize ){ char *pNew = (char *)sqlite3PageMalloc(pageSize); if( !pNew ){ rc = SQLITE_NOMEM; }else{ pager_reset(pPager); pPager->pageSize = pageSize; sqlite3PageFree(pPager->pTmpSpace); pPager->pTmpSpace = pNew; sqlite3PcacheSetPageSize(pPager->pPCache, pageSize); } } *pPageSize = (u16)pPager->pageSize; if( nReserve<0 ) nReserve = pPager->nReserve; assert( nReserve>=0 && nReserve<1000 ); pPager->nReserve = (i16)nReserve; pagerReportSize(pPager); } return rc; } /* ** Return a pointer to the "temporary page" buffer held internally ** by the pager. This is a buffer that is big enough to hold the ** entire content of a database page. This buffer is used internally ** during rollback and will be overwritten whenever a rollback ** occurs. But other modules are free to use it too, as long as ** no rollbacks are happening. */ void *sqlite3PagerTempSpace(Pager *pPager){ return pPager->pTmpSpace; } /* ** Attempt to set the maximum database page count if mxPage is positive. ** Make no changes if mxPage is zero or negative. And never reduce the ** maximum page count below the current size of the database. ** ** Regardless of mxPage, return the current maximum page count. */ int sqlite3PagerMaxPageCount(Pager *pPager, int mxPage){ int nPage; if( mxPage>0 ){ pPager->mxPgno = mxPage; } if( pPager->state!=PAGER_UNLOCK ){ sqlite3PagerPagecount(pPager, &nPage); assert( (int)pPager->mxPgno>=nPage ); } return pPager->mxPgno; } /* ** The following set of routines are used to disable the simulated ** I/O error mechanism. These routines are used to avoid simulated ** errors in places where we do not care about errors. ** ** Unless -DSQLITE_TEST=1 is used, these routines are all no-ops ** and generate no code. */ #ifdef SQLITE_TEST extern int sqlite3_io_error_pending; extern int sqlite3_io_error_hit; static int saved_cnt; void disable_simulated_io_errors(void){ saved_cnt = sqlite3_io_error_pending; sqlite3_io_error_pending = -1; } void enable_simulated_io_errors(void){ sqlite3_io_error_pending = saved_cnt; } #else # define disable_simulated_io_errors() # define enable_simulated_io_errors() #endif /* ** Read the first N bytes from the beginning of the file into memory ** that pDest points to. ** ** If the pager was opened on a transient file (zFilename==""), or ** opened on a file less than N bytes in size, the output buffer is ** zeroed and SQLITE_OK returned. The rationale for this is that this ** function is used to read database headers, and a new transient or ** zero sized database has a header than consists entirely of zeroes. ** ** If any IO error apart from SQLITE_IOERR_SHORT_READ is encountered, ** the error code is returned to the caller and the contents of the ** output buffer undefined. */ int sqlite3PagerReadFileheader(Pager *pPager, int N, unsigned char *pDest){ int rc = SQLITE_OK; memset(pDest, 0, N); assert( isOpen(pPager->fd) || pPager->tempFile ); /* This routine is only called by btree immediately after creating ** the Pager object. There has not been an opportunity to transition ** to WAL mode yet. */ assert( !pagerUseWal(pPager) ); #if 0 if( pagerUseWal(pPager) ){ int isInWal = 0; rc = sqlite3WalRead(pPager->pWal, 1, &isInWal, N, pDest); if( rc!=SQLITE_OK || isInWal ){ return rc; } } #endif if( isOpen(pPager->fd) ){ IOTRACE(("DBHDR %p 0 %d\n", pPager, N)) rc = sqlite3OsRead(pPager->fd, pDest, N, 0); if( rc==SQLITE_IOERR_SHORT_READ ){ rc = SQLITE_OK; } } return rc; } /* ** Return the total number of pages in the database file associated ** with pPager. Normally, this is calculated as (<db file size>/<page-size>). ** However, if the file is between 1 and <page-size> bytes in size, then ** this is considered a 1 page file. ** ** If the pager is in error state when this function is called, then the ** error state error code is returned and *pnPage left unchanged. Or, ** if the file system has to be queried for the size of the file and ** the query attempt returns an IO error, the IO error code is returned ** and *pnPage is left unchanged. ** ** Otherwise, if everything is successful, then SQLITE_OK is returned ** and *pnPage is set to the number of pages in the database. */ int sqlite3PagerPagecount(Pager *pPager, int *pnPage){ Pgno nPage = 0; /* Value to return via *pnPage */ /* Determine the number of pages in the file. Store this in nPage. */ if( pPager->dbSizeValid ){ nPage = pPager->dbSize; }else{ int rc; /* Error returned by OsFileSize() */ i64 n = 0; /* File size in bytes returned by OsFileSize() */ if( pagerUseWal(pPager) && pPager->state!=PAGER_UNLOCK ){ sqlite3WalDbsize(pPager->pWal, &nPage); } if( nPage==0 ){ assert( isOpen(pPager->fd) || pPager->tempFile ); if( isOpen(pPager->fd) ){ if( SQLITE_OK!=(rc = sqlite3OsFileSize(pPager->fd, &n)) ){ pager_error(pPager, rc); return rc; } } if( n>0 && n<pPager->pageSize ){ nPage = 1; }else{ nPage = (Pgno)(n / pPager->pageSize); } } if( pPager->state!=PAGER_UNLOCK ){ pPager->dbSize = nPage; pPager->dbFileSize = nPage; pPager->dbSizeValid = 1; } } /* If the current number of pages in the file is greater than the ** configured maximum pager number, increase the allowed limit so ** that the file can be read. */ if( nPage>pPager->mxPgno ){ pPager->mxPgno = (Pgno)nPage; } /* Set the output variable and return SQLITE_OK */ *pnPage = nPage; return SQLITE_OK; } /* ** Try to obtain a lock of type locktype on the database file. If ** a similar or greater lock is already held, this function is a no-op ** (returning SQLITE_OK immediately). ** ** Otherwise, attempt to obtain the lock using sqlite3OsLock(). Invoke ** the busy callback if the lock is currently not available. Repeat ** until the busy callback returns false or until the attempt to ** obtain the lock succeeds. ** ** Return SQLITE_OK on success and an error code if we cannot obtain ** the lock. If the lock is obtained successfully, set the Pager.state ** variable to locktype before returning. */ static int pager_wait_on_lock(Pager *pPager, int locktype){ int rc; /* Return code */ /* The OS lock values must be the same as the Pager lock values */ assert( PAGER_SHARED==SHARED_LOCK ); assert( PAGER_RESERVED==RESERVED_LOCK ); assert( PAGER_EXCLUSIVE==EXCLUSIVE_LOCK ); /* If the file is currently unlocked then the size must be unknown. It ** must not have been modified at this point. */ assert( pPager->state>=PAGER_SHARED || pPager->dbSizeValid==0 ); assert( pPager->state>=PAGER_SHARED || pPager->dbModified==0 ); /* Check that this is either a no-op (because the requested lock is ** already held, or one of the transistions that the busy-handler ** may be invoked during, according to the comment above ** sqlite3PagerSetBusyhandler(). */ assert( (pPager->state>=locktype) || (pPager->state==PAGER_UNLOCK && locktype==PAGER_SHARED) || (pPager->state==PAGER_RESERVED && locktype==PAGER_EXCLUSIVE) ); if( pPager->state>=locktype ){ rc = SQLITE_OK; }else{ do { rc = sqlite3OsLock(pPager->fd, locktype); }while( rc==SQLITE_BUSY && pPager->xBusyHandler(pPager->pBusyHandlerArg) ); if( rc==SQLITE_OK ){ pPager->state = (u8)locktype; IOTRACE(("LOCK %p %d\n", pPager, locktype)) } } return rc; } /* ** Function assertTruncateConstraint(pPager) checks that one of the ** following is true for all dirty pages currently in the page-cache: ** ** a) The page number is less than or equal to the size of the ** current database image, in pages, OR ** ** b) if the page content were written at this time, it would not ** be necessary to write the current content out to the sub-journal ** (as determined by function subjRequiresPage()). ** ** If the condition asserted by this function were not true, and the ** dirty page were to be discarded from the cache via the pagerStress() ** routine, pagerStress() would not write the current page content to ** the database file. If a savepoint transaction were rolled back after ** this happened, the correct behaviour would be to restore the current ** content of the page. However, since this content is not present in either ** the database file or the portion of the rollback journal and ** sub-journal rolled back the content could not be restored and the ** database image would become corrupt. It is therefore fortunate that ** this circumstance cannot arise. */ #if defined(SQLITE_DEBUG) static void assertTruncateConstraintCb(PgHdr *pPg){ assert( pPg->flags&PGHDR_DIRTY ); assert( !subjRequiresPage(pPg) || pPg->pgno<=pPg->pPager->dbSize ); } static void assertTruncateConstraint(Pager *pPager){ sqlite3PcacheIterateDirty(pPager->pPCache, assertTruncateConstraintCb); } #else # define assertTruncateConstraint(pPager) #endif /* ** Truncate the in-memory database file image to nPage pages. This ** function does not actually modify the database file on disk. It ** just sets the internal state of the pager object so that the ** truncation will be done when the current transaction is committed. */ void sqlite3PagerTruncateImage(Pager *pPager, Pgno nPage){ assert( pPager->dbSizeValid ); assert( pPager->dbSize>=nPage ); assert( pPager->state>=PAGER_RESERVED ); pPager->dbSize = nPage; assertTruncateConstraint(pPager); } /* ** This function is called before attempting a hot-journal rollback. It ** syncs the journal file to disk, then sets pPager->journalHdr to the ** size of the journal file so that the pager_playback() routine knows ** that the entire journal file has been synced. ** ** Syncing a hot-journal to disk before attempting to roll it back ensures ** that if a power-failure occurs during the rollback, the process that ** attempts rollback following system recovery sees the same journal ** content as this process. ** ** If everything goes as planned, SQLITE_OK is returned. Otherwise, ** an SQLite error code. */ static int pagerSyncHotJournal(Pager *pPager){ int rc = SQLITE_OK; if( !pPager->noSync ){ rc = sqlite3OsSync(pPager->jfd, SQLITE_SYNC_NORMAL); } if( rc==SQLITE_OK ){ rc = sqlite3OsFileSize(pPager->jfd, &pPager->journalHdr); } return rc; } /* ** Shutdown the page cache. Free all memory and close all files. ** ** If a transaction was in progress when this routine is called, that ** transaction is rolled back. All outstanding pages are invalidated ** and their memory is freed. Any attempt to use a page associated ** with this page cache after this function returns will likely ** result in a coredump. ** ** This function always succeeds. If a transaction is active an attempt ** is made to roll it back. If an error occurs during the rollback ** a hot journal may be left in the filesystem but no error is returned ** to the caller. */ int sqlite3PagerClose(Pager *pPager){ u8 *pTmp = (u8 *)pPager->pTmpSpace; disable_simulated_io_errors(); sqlite3BeginBenignMalloc(); pPager->errCode = 0; pPager->exclusiveMode = 0; #ifndef SQLITE_OMIT_WAL sqlite3WalClose(pPager->pWal, (pPager->noSync ? 0 : pPager->sync_flags), pPager->pageSize, pTmp ); pPager->pWal = 0; #endif pager_reset(pPager); if( MEMDB ){ pager_unlock(pPager); }else{ /* Set Pager.journalHdr to -1 for the benefit of the pager_playback() ** call which may be made from within pagerUnlockAndRollback(). If it ** is not -1, then the unsynced portion of an open journal file may ** be played back into the database. If a power failure occurs while ** this is happening, the database may become corrupt. */ if( isOpen(pPager->jfd) ){ pPager->errCode = pagerSyncHotJournal(pPager); } pagerUnlockAndRollback(pPager); } sqlite3EndBenignMalloc(); enable_simulated_io_errors(); PAGERTRACE(("CLOSE %d\n", PAGERID(pPager))); IOTRACE(("CLOSE %p\n", pPager)) sqlite3OsClose(pPager->jfd); sqlite3OsClose(pPager->fd); sqlite3PageFree(pTmp); sqlite3PcacheClose(pPager->pPCache); #ifdef SQLITE_HAS_CODEC if( pPager->xCodecFree ) pPager->xCodecFree(pPager->pCodec); #endif assert( !pPager->aSavepoint && !pPager->pInJournal ); assert( !isOpen(pPager->jfd) && !isOpen(pPager->sjfd) ); sqlite3_free(pPager); return SQLITE_OK; } #if !defined(NDEBUG) || defined(SQLITE_TEST) /* ** Return the page number for page pPg. */ Pgno sqlite3PagerPagenumber(DbPage *pPg){ return pPg->pgno; } #endif /* ** Increment the reference count for page pPg. */ void sqlite3PagerRef(DbPage *pPg){ sqlite3PcacheRef(pPg); } /* ** Sync the journal. In other words, make sure all the pages that have ** been written to the journal have actually reached the surface of the ** disk and can be restored in the event of a hot-journal rollback. ** ** If the Pager.needSync flag is not set, then this function is a ** no-op. Otherwise, the actions required depend on the journal-mode ** and the device characteristics of the the file-system, as follows: ** ** * If the journal file is an in-memory journal file, no action need ** be taken. ** ** * Otherwise, if the device does not support the SAFE_APPEND property, ** then the nRec field of the most recently written journal header ** is updated to contain the number of journal records that have ** been written following it. If the pager is operating in full-sync ** mode, then the journal file is synced before this field is updated. ** ** * If the device does not support the SEQUENTIAL property, then ** journal file is synced. ** ** Or, in pseudo-code: ** ** if( NOT <in-memory journal> ){ ** if( NOT SAFE_APPEND ){ ** if( <full-sync mode> ) xSync(<journal file>); ** <update nRec field> ** } ** if( NOT SEQUENTIAL ) xSync(<journal file>); ** } ** ** The Pager.needSync flag is never be set for temporary files, or any ** file operating in no-sync mode (Pager.noSync set to non-zero). ** ** If successful, this routine clears the PGHDR_NEED_SYNC flag of every ** page currently held in memory before returning SQLITE_OK. If an IO ** error is encountered, then the IO error code is returned to the caller. */ static int syncJournal(Pager *pPager){ if( pPager->needSync ){ assert( !pPager->tempFile ); if( pPager->journalMode!=PAGER_JOURNALMODE_MEMORY ){ int rc; /* Return code */ const int iDc = sqlite3OsDeviceCharacteristics(pPager->fd); assert( isOpen(pPager->jfd) ); if( 0==(iDc&SQLITE_IOCAP_SAFE_APPEND) ){ /* This block deals with an obscure problem. If the last connection ** that wrote to this database was operating in persistent-journal ** mode, then the journal file may at this point actually be larger ** than Pager.journalOff bytes. If the next thing in the journal ** file happens to be a journal-header (written as part of the ** previous connection's transaction), and a crash or power-failure ** occurs after nRec is updated but before this connection writes ** anything else to the journal file (or commits/rolls back its ** transaction), then SQLite may become confused when doing the ** hot-journal rollback following recovery. It may roll back all ** of this connections data, then proceed to rolling back the old, ** out-of-date data that follows it. Database corruption. ** ** To work around this, if the journal file does appear to contain ** a valid header following Pager.journalOff, then write a 0x00 ** byte to the start of it to prevent it from being recognized. ** ** Variable iNextHdrOffset is set to the offset at which this ** problematic header will occur, if it exists. aMagic is used ** as a temporary buffer to inspect the first couple of bytes of ** the potential journal header. */ i64 iNextHdrOffset; u8 aMagic[8]; u8 zHeader[sizeof(aJournalMagic)+4]; memcpy(zHeader, aJournalMagic, sizeof(aJournalMagic)); put32bits(&zHeader[sizeof(aJournalMagic)], pPager->nRec); iNextHdrOffset = journalHdrOffset(pPager); rc = sqlite3OsRead(pPager->jfd, aMagic, 8, iNextHdrOffset); if( rc==SQLITE_OK && 0==memcmp(aMagic, aJournalMagic, 8) ){ static const u8 zerobyte = 0; rc = sqlite3OsWrite(pPager->jfd, &zerobyte, 1, iNextHdrOffset); } if( rc!=SQLITE_OK && rc!=SQLITE_IOERR_SHORT_READ ){ return rc; } /* Write the nRec value into the journal file header. If in ** full-synchronous mode, sync the journal first. This ensures that ** all data has really hit the disk before nRec is updated to mark ** it as a candidate for rollback. ** ** This is not required if the persistent media supports the ** SAFE_APPEND property. Because in this case it is not possible ** for garbage data to be appended to the file, the nRec field ** is populated with 0xFFFFFFFF when the journal header is written ** and never needs to be updated. */ if( pPager->fullSync && 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){ PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager))); IOTRACE(("JSYNC %p\n", pPager)) rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags); if( rc!=SQLITE_OK ) return rc; } IOTRACE(("JHDR %p %lld\n", pPager, pPager->journalHdr)); rc = sqlite3OsWrite( pPager->jfd, zHeader, sizeof(zHeader), pPager->journalHdr ); if( rc!=SQLITE_OK ) return rc; } if( 0==(iDc&SQLITE_IOCAP_SEQUENTIAL) ){ PAGERTRACE(("SYNC journal of %d\n", PAGERID(pPager))); IOTRACE(("JSYNC %p\n", pPager)) rc = sqlite3OsSync(pPager->jfd, pPager->sync_flags| (pPager->sync_flags==SQLITE_SYNC_FULL?SQLITE_SYNC_DATAONLY:0) ); if( rc!=SQLITE_OK ) return rc; } } /* The journal file was just successfully synced. Set Pager.needSync ** to zero and clear the PGHDR_NEED_SYNC flag on all pagess. */ pPager->needSync = 0; pPager->journalStarted = 1; pPager->journalHdr = pPager->journalOff; sqlite3PcacheClearSyncFlags(pPager->pPCache); } return SQLITE_OK; } /* ** The argument is the first in a linked list of dirty pages connected ** by the PgHdr.pDirty pointer. This function writes each one of the ** in-memory pages in the list to the database file. The argument may ** be NULL, representing an empty list. In this case this function is ** a no-op. ** ** The pager must hold at least a RESERVED lock when this function ** is called. Before writing anything to the database file, this lock ** is upgraded to an EXCLUSIVE lock. If the lock cannot be obtained, ** SQLITE_BUSY is returned and no data is written to the database file. ** ** If the pager is a temp-file pager and the actual file-system file ** is not yet open, it is created and opened before any data is ** written out. ** ** Once the lock has been upgraded and, if necessary, the file opened, ** the pages are written out to the database file in list order. Writing ** a page is skipped if it meets either of the following criteria: ** ** * The page number is greater than Pager.dbSize, or ** * The PGHDR_DONT_WRITE flag is set on the page. ** ** If writing out a page causes the database file to grow, Pager.dbFileSize ** is updated accordingly. If page 1 is written out, then the value cached ** in Pager.dbFileVers[] is updated to match the new value stored in ** the database file. ** ** If everything is successful, SQLITE_OK is returned. If an IO error ** occurs, an IO error code is returned. Or, if the EXCLUSIVE lock cannot ** be obtained, SQLITE_BUSY is returned. */ static int pager_write_pagelist(PgHdr *pList){ Pager *pPager; /* Pager object */ int rc; /* Return code */ if( NEVER(pList==0) ) return SQLITE_OK; pPager = pList->pPager; /* At this point there may be either a RESERVED or EXCLUSIVE lock on the ** database file. If there is already an EXCLUSIVE lock, the following ** call is a no-op. ** ** Moving the lock from RESERVED to EXCLUSIVE actually involves going ** through an intermediate state PENDING. A PENDING lock prevents new ** readers from attaching to the database but is unsufficient for us to ** write. The idea of a PENDING lock is to prevent new readers from ** coming in while we wait for existing readers to clear. ** ** While the pager is in the RESERVED state, the original database file ** is unchanged and we can rollback without having to playback the ** journal into the original database file. Once we transition to ** EXCLUSIVE, it means the database file has been changed and any rollback ** will require a journal playback. */ assert( !pagerUseWal(pList->pPager) ); assert( pPager->state>=PAGER_RESERVED ); rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK); /* If the file is a temp-file has not yet been opened, open it now. It ** is not possible for rc to be other than SQLITE_OK if this branch ** is taken, as pager_wait_on_lock() is a no-op for temp-files. */ if( !isOpen(pPager->fd) ){ assert( pPager->tempFile && rc==SQLITE_OK ); rc = pagerOpentemp(pPager, pPager->fd, pPager->vfsFlags); } /* Before the first write, give the VFS a hint of what the final ** file size will be. */ if( pPager->dbSize > (pPager->dbOrigSize+1) && isOpen(pPager->fd) ){ sqlite3_int64 szFile = pPager->pageSize * (sqlite3_int64)pPager->dbSize; sqlite3OsFileControl(pPager->fd, SQLITE_FCNTL_SIZE_HINT, &szFile); } while( rc==SQLITE_OK && pList ){ Pgno pgno = pList->pgno; /* If there are dirty pages in the page cache with page numbers greater ** than Pager.dbSize, this means sqlite3PagerTruncateImage() was called to ** make the file smaller (presumably by auto-vacuum code). Do not write ** any such pages to the file. ** ** Also, do not write out any page that has the PGHDR_DONT_WRITE flag ** set (set by sqlite3PagerDontWrite()). */ if( pgno<=pPager->dbSize && 0==(pList->flags&PGHDR_DONT_WRITE) ){ i64 offset = (pgno-1)*(i64)pPager->pageSize; /* Offset to write */ char *pData; /* Data to write */ /* Encode the database */ CODEC2(pPager, pList->pData, pgno, 6, return SQLITE_NOMEM, pData); /* Write out the page data. */ rc = sqlite3OsWrite(pPager->fd, pData, pPager->pageSize, offset); /* If page 1 was just written, update Pager.dbFileVers to match ** the value now stored in the database file. If writing this ** page caused the database file to grow, update dbFileSize. */ if( pgno==1 ){ memcpy(&pPager->dbFileVers, &pData[24], sizeof(pPager->dbFileVers)); } if( pgno>pPager->dbFileSize ){ pPager->dbFileSize = pgno; } /* Update any backup objects copying the contents of this pager. */ sqlite3BackupUpdate(pPager->pBackup, pgno, (u8*)pList->pData); PAGERTRACE(("STORE %d page %d hash(%08x)\n", PAGERID(pPager), pgno, pager_pagehash(pList))); IOTRACE(("PGOUT %p %d\n", pPager, pgno)); PAGER_INCR(sqlite3_pager_writedb_count); PAGER_INCR(pPager->nWrite); }else{ PAGERTRACE(("NOSTORE %d page %d\n", PAGERID(pPager), pgno)); } #ifdef SQLITE_CHECK_PAGES pList->pageHash = pager_pagehash(pList); #endif pList = pList->pDirty; } return rc; } /* ** Ensure that the sub-journal file is open. If it is already open, this ** function is a no-op. ** ** SQLITE_OK is returned if everything goes according to plan. An ** SQLITE_IOERR_XXX error code is returned if a call to sqlite3OsOpen() ** fails. */ static int openSubJournal(Pager *pPager){ int rc = SQLITE_OK; if( !isOpen(pPager->sjfd) ){ if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY || pPager->subjInMemory ){ sqlite3MemJournalOpen(pPager->sjfd); }else{ rc = pagerOpentemp(pPager, pPager->sjfd, SQLITE_OPEN_SUBJOURNAL); } } return rc; } /* ** Append a record of the current state of page pPg to the sub-journal. ** It is the callers responsibility to use subjRequiresPage() to check ** that it is really required before calling this function. ** ** If successful, set the bit corresponding to pPg->pgno in the bitvecs ** for all open savepoints before returning. ** ** This function returns SQLITE_OK if everything is successful, an IO ** error code if the attempt to write to the sub-journal fails, or ** SQLITE_NOMEM if a malloc fails while setting a bit in a savepoint ** bitvec. */ static int subjournalPage(PgHdr *pPg){ int rc = SQLITE_OK; Pager *pPager = pPg->pPager; if( pPager->journalMode!=PAGER_JOURNALMODE_OFF ){ /* Open the sub-journal, if it has not already been opened */ assert( pPager->useJournal ); assert( isOpen(pPager->jfd) || pagerUseWal(pPager) ); assert( isOpen(pPager->sjfd) || pPager->nSubRec==0 ); assert( pagerUseWal(pPager) || pageInJournal(pPg) || pPg->pgno>pPager->dbOrigSize ); rc = openSubJournal(pPager); /* If the sub-journal was opened successfully (or was already open), ** write the journal record into the file. */ if( rc==SQLITE_OK ){ void *pData = pPg->pData; i64 offset = pPager->nSubRec*(4+pPager->pageSize); char *pData2; CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2); PAGERTRACE(("STMT-JOURNAL %d page %d\n", PAGERID(pPager), pPg->pgno)); rc = write32bits(pPager->sjfd, offset, pPg->pgno); if( rc==SQLITE_OK ){ rc = sqlite3OsWrite(pPager->sjfd, pData2, pPager->pageSize, offset+4); } } } if( rc==SQLITE_OK ){ pPager->nSubRec++; assert( pPager->nSavepoint>0 ); rc = addToSavepointBitvecs(pPager, pPg->pgno); } return rc; } /* ** This function is called by the pcache layer when it has reached some ** soft memory limit. The first argument is a pointer to a Pager object ** (cast as a void*). The pager is always 'purgeable' (not an in-memory ** database). The second argument is a reference to a page that is ** currently dirty but has no outstanding references. The page ** is always associated with the Pager object passed as the first ** argument. ** ** The job of this function is to make pPg clean by writing its contents ** out to the database file, if possible. This may involve syncing the ** journal file. ** ** If successful, sqlite3PcacheMakeClean() is called on the page and ** SQLITE_OK returned. If an IO error occurs while trying to make the ** page clean, the IO error code is returned. If the page cannot be ** made clean for some other reason, but no error occurs, then SQLITE_OK ** is returned by sqlite3PcacheMakeClean() is not called. */ static int pagerStress(void *p, PgHdr *pPg){ Pager *pPager = (Pager *)p; int rc = SQLITE_OK; assert( pPg->pPager==pPager ); assert( pPg->flags&PGHDR_DIRTY ); /* The doNotSyncSpill flag is set during times when doing a sync of ** journal (and adding a new header) is not allowed. This occurs ** during calls to sqlite3PagerWrite() while trying to journal multiple ** pages belonging to the same sector. ** ** The doNotSpill flag inhibits all cache spilling regardless of whether ** or not a sync is required. This is set during a rollback. ** ** Spilling is also inhibited when in an error state. */ if( pPager->errCode ) return SQLITE_OK; if( pPager->doNotSpill ) return SQLITE_OK; if( pPager->doNotSyncSpill && (pPg->flags & PGHDR_NEED_SYNC)!=0 ){ return SQLITE_OK; } pPg->pDirty = 0; if( pagerUseWal(pPager) ){ /* Write a single frame for this page to the log. */ if( subjRequiresPage(pPg) ){ rc = subjournalPage(pPg); } if( rc==SQLITE_OK ){ rc = pagerWalFrames(pPager, pPg, 0, 0, 0); } }else{ /* Sync the journal file if required. */ if( pPg->flags&PGHDR_NEED_SYNC ){ assert( !pPager->noSync ); rc = syncJournal(pPager); if( rc==SQLITE_OK && !(pPager->journalMode==PAGER_JOURNALMODE_MEMORY) && !(sqlite3OsDeviceCharacteristics(pPager->fd)&SQLITE_IOCAP_SAFE_APPEND) ){ pPager->nRec = 0; rc = writeJournalHdr(pPager); } } /* If the page number of this page is larger than the current size of ** the database image, it may need to be written to the sub-journal. ** This is because the call to pager_write_pagelist() below will not ** actually write data to the file in this case. ** ** Consider the following sequence of events: ** ** BEGIN; ** <journal page X> ** <modify page X> ** SAVEPOINT sp; ** <shrink database file to Y pages> ** pagerStress(page X) ** ROLLBACK TO sp; ** ** If (X>Y), then when pagerStress is called page X will not be written ** out to the database file, but will be dropped from the cache. Then, ** following the "ROLLBACK TO sp" statement, reading page X will read ** data from the database file. This will be the copy of page X as it ** was when the transaction started, not as it was when "SAVEPOINT sp" ** was executed. ** ** The solution is to write the current data for page X into the ** sub-journal file now (if it is not already there), so that it will ** be restored to its current value when the "ROLLBACK TO sp" is ** executed. */ if( NEVER( rc==SQLITE_OK && pPg->pgno>pPager->dbSize && subjRequiresPage(pPg) ) ){ rc = subjournalPage(pPg); } /* Write the contents of the page out to the database file. */ if( rc==SQLITE_OK ){ rc = pager_write_pagelist(pPg); } } /* Mark the page as clean. */ if( rc==SQLITE_OK ){ PAGERTRACE(("STRESS %d page %d\n", PAGERID(pPager), pPg->pgno)); sqlite3PcacheMakeClean(pPg); } return pager_error(pPager, rc); } /* ** Allocate and initialize a new Pager object and put a pointer to it ** in *ppPager. The pager should eventually be freed by passing it ** to sqlite3PagerClose(). ** ** The zFilename argument is the path to the database file to open. ** If zFilename is NULL then a randomly-named temporary file is created ** and used as the file to be cached. Temporary files are be deleted ** automatically when they are closed. If zFilename is ":memory:" then ** all information is held in cache. It is never written to disk. ** This can be used to implement an in-memory database. ** ** The nExtra parameter specifies the number of bytes of space allocated ** along with each page reference. This space is available to the user ** via the sqlite3PagerGetExtra() API. ** ** The flags argument is used to specify properties that affect the ** operation of the pager. It should be passed some bitwise combination ** of the PAGER_OMIT_JOURNAL and PAGER_NO_READLOCK flags. ** ** The vfsFlags parameter is a bitmask to pass to the flags parameter ** of the xOpen() method of the supplied VFS when opening files. ** ** If the pager object is allocated and the specified file opened ** successfully, SQLITE_OK is returned and *ppPager set to point to ** the new pager object. If an error occurs, *ppPager is set to NULL ** and error code returned. This function may return SQLITE_NOMEM ** (sqlite3Malloc() is used to allocate memory), SQLITE_CANTOPEN or ** various SQLITE_IO_XXX errors. */ int sqlite3PagerOpen( sqlite3_vfs *pVfs, /* The virtual file system to use */ Pager **ppPager, /* OUT: Return the Pager structure here */ const char *zFilename, /* Name of the database file to open */ int nExtra, /* Extra bytes append to each in-memory page */ int flags, /* flags controlling this file */ int vfsFlags, /* flags passed through to sqlite3_vfs.xOpen() */ void (*xReinit)(DbPage*) /* Function to reinitialize pages */ ){ u8 *pPtr; Pager *pPager = 0; /* Pager object to allocate and return */ int rc = SQLITE_OK; /* Return code */ int tempFile = 0; /* True for temp files (incl. in-memory files) */ int memDb = 0; /* True if this is an in-memory file */ int readOnly = 0; /* True if this is a read-only file */ int journalFileSize; /* Bytes to allocate for each journal fd */ char *zPathname = 0; /* Full path to database file */ int nPathname = 0; /* Number of bytes in zPathname */ int useJournal = (flags & PAGER_OMIT_JOURNAL)==0; /* False to omit journal */ int noReadlock = (flags & PAGER_NO_READLOCK)!=0; /* True to omit read-lock */ int pcacheSize = sqlite3PcacheSize(); /* Bytes to allocate for PCache */ u16 szPageDflt = SQLITE_DEFAULT_PAGE_SIZE; /* Default page size */ /* Figure out how much space is required for each journal file-handle ** (there are two of them, the main journal and the sub-journal). This ** is the maximum space required for an in-memory journal file handle ** and a regular journal file-handle. Note that a "regular journal-handle" ** may be a wrapper capable of caching the first portion of the journal ** file in memory to implement the atomic-write optimization (see ** source file journal.c). */ if( sqlite3JournalSize(pVfs)>sqlite3MemJournalSize() ){ journalFileSize = ROUND8(sqlite3JournalSize(pVfs)); }else{ journalFileSize = ROUND8(sqlite3MemJournalSize()); } /* Set the output variable to NULL in case an error occurs. */ *ppPager = 0; /* Compute and store the full pathname in an allocated buffer pointed ** to by zPathname, length nPathname. Or, if this is a temporary file, ** leave both nPathname and zPathname set to 0. */ if( zFilename && zFilename[0] ){ nPathname = pVfs->mxPathname+1; zPathname = sqlite3Malloc(nPathname*2); if( zPathname==0 ){ return SQLITE_NOMEM; } #ifndef SQLITE_OMIT_MEMORYDB if( strcmp(zFilename,":memory:")==0 ){ memDb = 1; zPathname[0] = 0; }else #endif { zPathname[0] = 0; /* Make sure initialized even if FullPathname() fails */ rc = sqlite3OsFullPathname(pVfs, zFilename, nPathname, zPathname); } nPathname = sqlite3Strlen30(zPathname); if( rc==SQLITE_OK && nPathname+8>pVfs->mxPathname ){ /* This branch is taken when the journal path required by ** the database being opened will be more than pVfs->mxPathname ** bytes in length. This means the database cannot be opened, ** as it will not be possible to open the journal file or even ** check for a hot-journal before reading. */ rc = SQLITE_CANTOPEN_BKPT; } if( rc!=SQLITE_OK ){ sqlite3_free(zPathname); return rc; } } /* Allocate memory for the Pager structure, PCache object, the ** three file descriptors, the database file name and the journal ** file name. The layout in memory is as follows: ** ** Pager object (sizeof(Pager) bytes) ** PCache object (sqlite3PcacheSize() bytes) ** Database file handle (pVfs->szOsFile bytes) ** Sub-journal file handle (journalFileSize bytes) ** Main journal file handle (journalFileSize bytes) ** Database file name (nPathname+1 bytes) ** Journal file name (nPathname+8+1 bytes) */ pPtr = (u8 *)sqlite3MallocZero( ROUND8(sizeof(*pPager)) + /* Pager structure */ ROUND8(pcacheSize) + /* PCache object */ ROUND8(pVfs->szOsFile) + /* The main db file */ journalFileSize * 2 + /* The two journal files */ nPathname + 1 + /* zFilename */ nPathname + 8 + 1 /* zJournal */ ); assert( EIGHT_BYTE_ALIGNMENT(SQLITE_INT_TO_PTR(journalFileSize)) ); if( !pPtr ){ sqlite3_free(zPathname); return SQLITE_NOMEM; } pPager = (Pager*)(pPtr); pPager->pPCache = (PCache*)(pPtr += ROUND8(sizeof(*pPager))); pPager->fd = (sqlite3_file*)(pPtr += ROUND8(pcacheSize)); pPager->sjfd = (sqlite3_file*)(pPtr += ROUND8(pVfs->szOsFile)); pPager->jfd = (sqlite3_file*)(pPtr += journalFileSize); pPager->zFilename = (char*)(pPtr += journalFileSize); assert( EIGHT_BYTE_ALIGNMENT(pPager->jfd) ); /* Fill in the Pager.zFilename and Pager.zJournal buffers, if required. */ if( zPathname ){ pPager->zJournal = (char*)(pPtr += nPathname + 1); memcpy(pPager->zFilename, zPathname, nPathname); memcpy(pPager->zJournal, zPathname, nPathname); memcpy(&pPager->zJournal[nPathname], "-journal", 8); if( pPager->zFilename[0]==0 ) pPager->zJournal[0] = 0; sqlite3_free(zPathname); } pPager->pVfs = pVfs; pPager->vfsFlags = vfsFlags; /* Open the pager file. */ if( zFilename && zFilename[0] && !memDb ){ int fout = 0; /* VFS flags returned by xOpen() */ rc = sqlite3OsOpen(pVfs, pPager->zFilename, pPager->fd, vfsFlags, &fout); readOnly = (fout&SQLITE_OPEN_READONLY); /* If the file was successfully opened for read/write access, ** choose a default page size in case we have to create the ** database file. The default page size is the maximum of: ** ** + SQLITE_DEFAULT_PAGE_SIZE, ** + The value returned by sqlite3OsSectorSize() ** + The largest page size that can be written atomically. */ if( rc==SQLITE_OK && !readOnly ){ setSectorSize(pPager); assert(SQLITE_DEFAULT_PAGE_SIZE<=SQLITE_MAX_DEFAULT_PAGE_SIZE); if( szPageDflt<pPager->sectorSize ){ if( pPager->sectorSize>SQLITE_MAX_DEFAULT_PAGE_SIZE ){ szPageDflt = SQLITE_MAX_DEFAULT_PAGE_SIZE; }else{ szPageDflt = (u16)pPager->sectorSize; } } #ifdef SQLITE_ENABLE_ATOMIC_WRITE { int iDc = sqlite3OsDeviceCharacteristics(pPager->fd); int ii; assert(SQLITE_IOCAP_ATOMIC512==(512>>8)); assert(SQLITE_IOCAP_ATOMIC64K==(65536>>8)); assert(SQLITE_MAX_DEFAULT_PAGE_SIZE<=65536); for(ii=szPageDflt; ii<=SQLITE_MAX_DEFAULT_PAGE_SIZE; ii=ii*2){ if( iDc&(SQLITE_IOCAP_ATOMIC|(ii>>8)) ){ szPageDflt = ii; } } } #endif } }else{ /* If a temporary file is requested, it is not opened immediately. ** In this case we accept the default page size and delay actually ** opening the file until the first call to OsWrite(). ** ** This branch is also run for an in-memory database. An in-memory ** database is the same as a temp-file that is never written out to ** disk and uses an in-memory rollback journal. */ tempFile = 1; pPager->state = PAGER_EXCLUSIVE; readOnly = (vfsFlags&SQLITE_OPEN_READONLY); } /* The following call to PagerSetPagesize() serves to set the value of ** Pager.pageSize and to allocate the Pager.pTmpSpace buffer. */ if( rc==SQLITE_OK ){ assert( pPager->memDb==0 ); rc = sqlite3PagerSetPagesize(pPager, &szPageDflt, -1); testcase( rc!=SQLITE_OK ); } /* If an error occurred in either of the blocks above, free the ** Pager structure and close the file. */ if( rc!=SQLITE_OK ){ assert( !pPager->pTmpSpace ); sqlite3OsClose(pPager->fd); sqlite3_free(pPager); return rc; } /* Initialize the PCache object. */ assert( nExtra<1000 ); nExtra = ROUND8(nExtra); sqlite3PcacheOpen(szPageDflt, nExtra, !memDb, !memDb?pagerStress:0, (void *)pPager, pPager->pPCache); PAGERTRACE(("OPEN %d %s\n", FILEHANDLEID(pPager->fd), pPager->zFilename)); IOTRACE(("OPEN %p %s\n", pPager, pPager->zFilename)) pPager->useJournal = (u8)useJournal; pPager->noReadlock = (noReadlock && readOnly) ?1:0; /* pPager->stmtOpen = 0; */ /* pPager->stmtInUse = 0; */ /* pPager->nRef = 0; */ pPager->dbSizeValid = (u8)memDb; /* pPager->stmtSize = 0; */ /* pPager->stmtJSize = 0; */ /* pPager->nPage = 0; */ pPager->mxPgno = SQLITE_MAX_PAGE_COUNT; /* pPager->state = PAGER_UNLOCK; */ assert( pPager->state == (tempFile ? PAGER_EXCLUSIVE : PAGER_UNLOCK) ); /* pPager->errMask = 0; */ pPager->tempFile = (u8)tempFile; assert( tempFile==PAGER_LOCKINGMODE_NORMAL || tempFile==PAGER_LOCKINGMODE_EXCLUSIVE ); assert( PAGER_LOCKINGMODE_EXCLUSIVE==1 ); pPager->exclusiveMode = (u8)tempFile; pPager->changeCountDone = pPager->tempFile; pPager->memDb = (u8)memDb; pPager->readOnly = (u8)readOnly; /* pPager->needSync = 0; */ assert( useJournal || pPager->tempFile ); pPager->noSync = pPager->tempFile; pPager->fullSync = pPager->noSync ?0:1; pPager->sync_flags = SQLITE_SYNC_NORMAL; /* pPager->pFirst = 0; */ /* pPager->pFirstSynced = 0; */ /* pPager->pLast = 0; */ pPager->nExtra = (u16)nExtra; pPager->journalSizeLimit = SQLITE_DEFAULT_JOURNAL_SIZE_LIMIT; assert( isOpen(pPager->fd) || tempFile ); setSectorSize(pPager); if( !useJournal ){ pPager->journalMode = PAGER_JOURNALMODE_OFF; }else if( memDb ){ pPager->journalMode = PAGER_JOURNALMODE_MEMORY; } /* pPager->xBusyHandler = 0; */ /* pPager->pBusyHandlerArg = 0; */ pPager->xReiniter = xReinit; /* memset(pPager->aHash, 0, sizeof(pPager->aHash)); */ *ppPager = pPager; return SQLITE_OK; } /* ** This function is called after transitioning from PAGER_UNLOCK to ** PAGER_SHARED state. It tests if there is a hot journal present in ** the file-system for the given pager. A hot journal is one that ** needs to be played back. According to this function, a hot-journal ** file exists if the following criteria are met: ** ** * The journal file exists in the file system, and ** * No process holds a RESERVED or greater lock on the database file, and ** * The database file itself is greater than 0 bytes in size, and ** * The first byte of the journal file exists and is not 0x00. ** ** If the current size of the database file is 0 but a journal file ** exists, that is probably an old journal left over from a prior ** database with the same name. In this case the journal file is ** just deleted using OsDelete, *pExists is set to 0 and SQLITE_OK ** is returned. ** ** This routine does not check if there is a master journal filename ** at the end of the file. If there is, and that master journal file ** does not exist, then the journal file is not really hot. In this ** case this routine will return a false-positive. The pager_playback() ** routine will discover that the journal file is not really hot and ** will not roll it back. ** ** If a hot-journal file is found to exist, *pExists is set to 1 and ** SQLITE_OK returned. If no hot-journal file is present, *pExists is ** set to 0 and SQLITE_OK returned. If an IO error occurs while trying ** to determine whether or not a hot-journal file exists, the IO error ** code is returned and the value of *pExists is undefined. */ static int hasHotJournal(Pager *pPager, int *pExists){ sqlite3_vfs * const pVfs = pPager->pVfs; int rc = SQLITE_OK; /* Return code */ int exists = 1; /* True if a journal file is present */ int jrnlOpen = !!isOpen(pPager->jfd); assert( pPager!=0 ); assert( pPager->useJournal ); assert( isOpen(pPager->fd) ); assert( pPager->state <= PAGER_SHARED ); assert( jrnlOpen==0 || ( sqlite3OsDeviceCharacteristics(pPager->jfd) & SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN )); *pExists = 0; if( !jrnlOpen ){ rc = sqlite3OsAccess(pVfs, pPager->zJournal, SQLITE_ACCESS_EXISTS, &exists); } if( rc==SQLITE_OK && exists ){ int locked; /* True if some process holds a RESERVED lock */ /* Race condition here: Another process might have been holding the ** the RESERVED lock and have a journal open at the sqlite3OsAccess() ** call above, but then delete the journal and drop the lock before ** we get to the following sqlite3OsCheckReservedLock() call. If that ** is the case, this routine might think there is a hot journal when ** in fact there is none. This results in a false-positive which will ** be dealt with by the playback routine. Ticket #3883. */ rc = sqlite3OsCheckReservedLock(pPager->fd, &locked); if( rc==SQLITE_OK && !locked ){ int nPage; /* Check the size of the database file. If it consists of 0 pages, ** then delete the journal file. See the header comment above for ** the reasoning here. Delete the obsolete journal file under ** a RESERVED lock to avoid race conditions and to avoid violating ** [H33020]. */ rc = sqlite3PagerPagecount(pPager, &nPage); if( rc==SQLITE_OK ){ if( nPage==0 ){ sqlite3BeginBenignMalloc(); if( sqlite3OsLock(pPager->fd, RESERVED_LOCK)==SQLITE_OK ){ sqlite3OsDelete(pVfs, pPager->zJournal, 0); sqlite3OsUnlock(pPager->fd, SHARED_LOCK); } sqlite3EndBenignMalloc(); }else{ /* The journal file exists and no other connection has a reserved ** or greater lock on the database file. Now check that there is ** at least one non-zero bytes at the start of the journal file. ** If there is, then we consider this journal to be hot. If not, ** it can be ignored. */ if( !jrnlOpen ){ int f = SQLITE_OPEN_READONLY|SQLITE_OPEN_MAIN_JOURNAL; rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &f); } if( rc==SQLITE_OK ){ u8 first = 0; rc = sqlite3OsRead(pPager->jfd, (void *)&first, 1, 0); if( rc==SQLITE_IOERR_SHORT_READ ){ rc = SQLITE_OK; } if( !jrnlOpen ){ sqlite3OsClose(pPager->jfd); } *pExists = (first!=0); }else if( rc==SQLITE_CANTOPEN ){ /* If we cannot open the rollback journal file in order to see if ** its has a zero header, that might be due to an I/O error, or ** it might be due to the race condition described above and in ** ticket #3883. Either way, assume that the journal is hot. ** This might be a false positive. But if it is, then the ** automatic journal playback and recovery mechanism will deal ** with it under an EXCLUSIVE lock where we do not need to ** worry so much with race conditions. */ *pExists = 1; rc = SQLITE_OK; } } } } } return rc; } /* ** This function is called to obtain a shared lock on the database file. ** It is illegal to call sqlite3PagerAcquire() until after this function ** has been successfully called. If a shared-lock is already held when ** this function is called, it is a no-op. ** ** The following operations are also performed by this function. ** ** 1) If the pager is currently in PAGER_UNLOCK state (no lock held ** on the database file), then an attempt is made to obtain a ** SHARED lock on the database file. Immediately after obtaining ** the SHARED lock, the file-system is checked for a hot-journal, ** which is played back if present. Following any hot-journal ** rollback, the contents of the cache are validated by checking ** the 'change-counter' field of the database file header and ** discarded if they are found to be invalid. ** ** 2) If the pager is running in exclusive-mode, and there are currently ** no outstanding references to any pages, and is in the error state, ** then an attempt is made to clear the error state by discarding ** the contents of the page cache and rolling back any open journal ** file. ** ** If the operation described by (2) above is not attempted, and if the ** pager is in an error state other than SQLITE_FULL when this is called, ** the error state error code is returned. It is permitted to read the ** database when in SQLITE_FULL error state. ** ** Otherwise, if everything is successful, SQLITE_OK is returned. If an ** IO error occurs while locking the database, checking for a hot-journal ** file or rolling back a journal file, the IO error code is returned. */ int sqlite3PagerSharedLock(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ int isErrorReset = 0; /* True if recovering from error state */ /* This routine is only called from b-tree and only when there are no ** outstanding pages */ assert( sqlite3PcacheRefCount(pPager->pPCache)==0 ); if( NEVER(MEMDB && pPager->errCode) ){ return pPager->errCode; } /* If this database is in an error-state, now is a chance to clear ** the error. Discard the contents of the pager-cache and rollback ** any hot journal in the file-system. */ if( pPager->errCode ){ if( isOpen(pPager->jfd) || pPager->zJournal ){ isErrorReset = 1; } pPager->errCode = SQLITE_OK; pager_reset(pPager); } if( pagerUseWal(pPager) ){ rc = pagerBeginReadTransaction(pPager); }else if( pPager->state==PAGER_UNLOCK || isErrorReset ){ sqlite3_vfs * const pVfs = pPager->pVfs; int isHotJournal = 0; assert( !MEMDB ); assert( sqlite3PcacheRefCount(pPager->pPCache)==0 ); if( pPager->noReadlock ){ assert( pPager->readOnly ); pPager->state = PAGER_SHARED; }else{ rc = pager_wait_on_lock(pPager, SHARED_LOCK); if( rc!=SQLITE_OK ){ assert( pPager->state==PAGER_UNLOCK ); return pager_error(pPager, rc); } } assert( pPager->state>=SHARED_LOCK ); /* If a journal file exists, and there is no RESERVED lock on the ** database file, then it either needs to be played back or deleted. */ if( !isErrorReset ){ assert( pPager->state <= PAGER_SHARED ); rc = hasHotJournal(pPager, &isHotJournal); if( rc!=SQLITE_OK ){ goto failed; } } if( isErrorReset || isHotJournal ){ /* Get an EXCLUSIVE lock on the database file. At this point it is ** important that a RESERVED lock is not obtained on the way to the ** EXCLUSIVE lock. If it were, another process might open the ** database file, detect the RESERVED lock, and conclude that the ** database is safe to read while this process is still rolling the ** hot-journal back. ** ** Because the intermediate RESERVED lock is not requested, any ** other process attempting to access the database file will get to ** this point in the code and fail to obtain its own EXCLUSIVE lock ** on the database file. */ if( pPager->state<EXCLUSIVE_LOCK ){ rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK); if( rc!=SQLITE_OK ){ rc = pager_error(pPager, rc); goto failed; } pPager->state = PAGER_EXCLUSIVE; } /* Open the journal for read/write access. This is because in ** exclusive-access mode the file descriptor will be kept open and ** possibly used for a transaction later on. On some systems, the ** OsTruncate() call used in exclusive-access mode also requires ** a read/write file handle. */ if( !isOpen(pPager->jfd) ){ int res; rc = sqlite3OsAccess(pVfs,pPager->zJournal,SQLITE_ACCESS_EXISTS,&res); if( rc==SQLITE_OK ){ if( res ){ int fout = 0; int f = SQLITE_OPEN_READWRITE|SQLITE_OPEN_MAIN_JOURNAL; assert( !pPager->tempFile ); rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, f, &fout); assert( rc!=SQLITE_OK || isOpen(pPager->jfd) ); if( rc==SQLITE_OK && fout&SQLITE_OPEN_READONLY ){ rc = SQLITE_CANTOPEN_BKPT; sqlite3OsClose(pPager->jfd); } }else{ /* If the journal does not exist, it usually means that some ** other connection managed to get in and roll it back before ** this connection obtained the exclusive lock above. Or, it ** may mean that the pager was in the error-state when this ** function was called and the journal file does not exist. */ rc = pager_end_transaction(pPager, 0); } } } if( rc!=SQLITE_OK ){ goto failed; } /* Reset the journal status fields to indicates that we have no ** rollback journal at this time. */ pPager->journalStarted = 0; pPager->journalOff = 0; pPager->setMaster = 0; pPager->journalHdr = 0; /* Make sure the journal file has been synced to disk. */ /* Playback and delete the journal. Drop the database write ** lock and reacquire the read lock. Purge the cache before ** playing back the hot-journal so that we don't end up with ** an inconsistent cache. Sync the hot journal before playing ** it back since the process that crashed and left the hot journal ** probably did not sync it and we are required to always sync ** the journal before playing it back. */ if( isOpen(pPager->jfd) ){ rc = pagerSyncHotJournal(pPager); if( rc==SQLITE_OK ){ rc = pager_playback(pPager, 1); } if( rc!=SQLITE_OK ){ rc = pager_error(pPager, rc); goto failed; } } assert( (pPager->state==PAGER_SHARED) || (pPager->exclusiveMode && pPager->state>PAGER_SHARED) ); } if( pPager->pBackup || sqlite3PcachePagecount(pPager->pPCache)>0 ){ /* The shared-lock has just been acquired on the database file ** and there are already pages in the cache (from a previous ** read or write transaction). Check to see if the database ** has been modified. If the database has changed, flush the ** cache. ** ** Database changes is detected by looking at 15 bytes beginning ** at offset 24 into the file. The first 4 of these 16 bytes are ** a 32-bit counter that is incremented with each change. The ** other bytes change randomly with each file change when ** a codec is in use. ** ** There is a vanishingly small chance that a change will not be ** detected. The chance of an undetected change is so small that ** it can be neglected. */ int nPage = 0; char dbFileVers[sizeof(pPager->dbFileVers)]; sqlite3PagerPagecount(pPager, &nPage); if( pPager->errCode ){ rc = pPager->errCode; goto failed; } if( nPage>0 ){ IOTRACE(("CKVERS %p %d\n", pPager, sizeof(dbFileVers))); rc = sqlite3OsRead(pPager->fd, &dbFileVers, sizeof(dbFileVers), 24); if( rc!=SQLITE_OK ){ goto failed; } }else{ memset(dbFileVers, 0, sizeof(dbFileVers)); } if( memcmp(pPager->dbFileVers, dbFileVers, sizeof(dbFileVers))!=0 ){ pager_reset(pPager); } } assert( pPager->exclusiveMode || pPager->state==PAGER_SHARED ); /* If there is a WAL file in the file-system, open this database in WAL ** mode. Otherwise, the following function call is a no-op. */ rc = pagerOpenWalIfPresent(pPager); } failed: if( rc!=SQLITE_OK ){ /* pager_unlock() is a no-op for exclusive mode and in-memory databases. */ pager_unlock(pPager); } return rc; } /* ** If the reference count has reached zero, rollback any active ** transaction and unlock the pager. ** ** Except, in locking_mode=EXCLUSIVE when there is nothing to in ** the rollback journal, the unlock is not performed and there is ** nothing to rollback, so this routine is a no-op. */ static void pagerUnlockIfUnused(Pager *pPager){ if( (sqlite3PcacheRefCount(pPager->pPCache)==0) && (!pPager->exclusiveMode || pPager->journalOff>0) ){ pagerUnlockAndRollback(pPager); } } /* ** Acquire a reference to page number pgno in pager pPager (a page ** reference has type DbPage*). If the requested reference is ** successfully obtained, it is copied to *ppPage and SQLITE_OK returned. ** ** If the requested page is already in the cache, it is returned. ** Otherwise, a new page object is allocated and populated with data ** read from the database file. In some cases, the pcache module may ** choose not to allocate a new page object and may reuse an existing ** object with no outstanding references. ** ** The extra data appended to a page is always initialized to zeros the ** first time a page is loaded into memory. If the page requested is ** already in the cache when this function is called, then the extra ** data is left as it was when the page object was last used. ** ** If the database image is smaller than the requested page or if a ** non-zero value is passed as the noContent parameter and the ** requested page is not already stored in the cache, then no ** actual disk read occurs. In this case the memory image of the ** page is initialized to all zeros. ** ** If noContent is true, it means that we do not care about the contents ** of the page. This occurs in two seperate scenarios: ** ** a) When reading a free-list leaf page from the database, and ** ** b) When a savepoint is being rolled back and we need to load ** a new page into the cache to be filled with the data read ** from the savepoint journal. ** ** If noContent is true, then the data returned is zeroed instead of ** being read from the database. Additionally, the bits corresponding ** to pgno in Pager.pInJournal (bitvec of pages already written to the ** journal file) and the PagerSavepoint.pInSavepoint bitvecs of any open ** savepoints are set. This means if the page is made writable at any ** point in the future, using a call to sqlite3PagerWrite(), its contents ** will not be journaled. This saves IO. ** ** The acquisition might fail for several reasons. In all cases, ** an appropriate error code is returned and *ppPage is set to NULL. ** ** See also sqlite3PagerLookup(). Both this routine and Lookup() attempt ** to find a page in the in-memory cache first. If the page is not already ** in memory, this routine goes to disk to read it in whereas Lookup() ** just returns 0. This routine acquires a read-lock the first time it ** has to go to disk, and could also playback an old journal if necessary. ** Since Lookup() never goes to disk, it never has to deal with locks ** or journal files. */ int sqlite3PagerAcquire( Pager *pPager, /* The pager open on the database file */ Pgno pgno, /* Page number to fetch */ DbPage **ppPage, /* Write a pointer to the page here */ int noContent /* Do not bother reading content from disk if true */ ){ int rc; PgHdr *pPg; assert( assert_pager_state(pPager) ); assert( pPager->state>PAGER_UNLOCK ); if( pgno==0 ){ return SQLITE_CORRUPT_BKPT; } /* If the pager is in the error state, return an error immediately. ** Otherwise, request the page from the PCache layer. */ if( pPager->errCode!=SQLITE_OK && pPager->errCode!=SQLITE_FULL ){ rc = pPager->errCode; }else{ rc = sqlite3PcacheFetch(pPager->pPCache, pgno, 1, ppPage); } if( rc!=SQLITE_OK ){ /* Either the call to sqlite3PcacheFetch() returned an error or the ** pager was already in the error-state when this function was called. ** Set pPg to 0 and jump to the exception handler. */ pPg = 0; goto pager_acquire_err; } assert( (*ppPage)->pgno==pgno ); assert( (*ppPage)->pPager==pPager || (*ppPage)->pPager==0 ); if( (*ppPage)->pPager && !noContent ){ /* In this case the pcache already contains an initialized copy of ** the page. Return without further ado. */ assert( pgno<=PAGER_MAX_PGNO && pgno!=PAGER_MJ_PGNO(pPager) ); PAGER_INCR(pPager->nHit); return SQLITE_OK; }else{ /* The pager cache has created a new page. Its content needs to ** be initialized. */ int nMax; PAGER_INCR(pPager->nMiss); pPg = *ppPage; pPg->pPager = pPager; /* The maximum page number is 2^31. Return SQLITE_CORRUPT if a page ** number greater than this, or the unused locking-page, is requested. */ if( pgno>PAGER_MAX_PGNO || pgno==PAGER_MJ_PGNO(pPager) ){ rc = SQLITE_CORRUPT_BKPT; goto pager_acquire_err; } rc = sqlite3PagerPagecount(pPager, &nMax); if( rc!=SQLITE_OK ){ goto pager_acquire_err; } if( MEMDB || nMax<(int)pgno || noContent || !isOpen(pPager->fd) ){ if( pgno>pPager->mxPgno ){ rc = SQLITE_FULL; goto pager_acquire_err; } if( noContent ){ /* Failure to set the bits in the InJournal bit-vectors is benign. ** It merely means that we might do some extra work to journal a ** page that does not need to be journaled. Nevertheless, be sure ** to test the case where a malloc error occurs while trying to set ** a bit in a bit vector. */ sqlite3BeginBenignMalloc(); if( pgno<=pPager->dbOrigSize ){ TESTONLY( rc = ) sqlite3BitvecSet(pPager->pInJournal, pgno); testcase( rc==SQLITE_NOMEM ); } TESTONLY( rc = ) addToSavepointBitvecs(pPager, pgno); testcase( rc==SQLITE_NOMEM ); sqlite3EndBenignMalloc(); } memset(pPg->pData, 0, pPager->pageSize); IOTRACE(("ZERO %p %d\n", pPager, pgno)); }else{ assert( pPg->pPager==pPager ); rc = readDbPage(pPg); if( rc!=SQLITE_OK ){ goto pager_acquire_err; } } #ifdef SQLITE_CHECK_PAGES pPg->pageHash = pager_pagehash(pPg); #endif } return SQLITE_OK; pager_acquire_err: assert( rc!=SQLITE_OK ); if( pPg ){ sqlite3PcacheDrop(pPg); } pagerUnlockIfUnused(pPager); *ppPage = 0; return rc; } /* ** Acquire a page if it is already in the in-memory cache. Do ** not read the page from disk. Return a pointer to the page, ** or 0 if the page is not in cache. Also, return 0 if the ** pager is in PAGER_UNLOCK state when this function is called, ** or if the pager is in an error state other than SQLITE_FULL. ** ** See also sqlite3PagerGet(). The difference between this routine ** and sqlite3PagerGet() is that _get() will go to the disk and read ** in the page if the page is not already in cache. This routine ** returns NULL if the page is not in cache or if a disk I/O error ** has ever happened. */ DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){ PgHdr *pPg = 0; assert( pPager!=0 ); assert( pgno!=0 ); assert( pPager->pPCache!=0 ); assert( pPager->state > PAGER_UNLOCK ); sqlite3PcacheFetch(pPager->pPCache, pgno, 0, &pPg); return pPg; } /* ** Release a page reference. ** ** If the number of references to the page drop to zero, then the ** page is added to the LRU list. When all references to all pages ** are released, a rollback occurs and the lock on the database is ** removed. */ void sqlite3PagerUnref(DbPage *pPg){ if( pPg ){ Pager *pPager = pPg->pPager; sqlite3PcacheRelease(pPg); pagerUnlockIfUnused(pPager); } } /* ** This function is called at the start of every write transaction. ** There must already be a RESERVED or EXCLUSIVE lock on the database ** file when this routine is called. ** ** Open the journal file for pager pPager and write a journal header ** to the start of it. If there are active savepoints, open the sub-journal ** as well. This function is only used when the journal file is being ** opened to write a rollback log for a transaction. It is not used ** when opening a hot journal file to roll it back. ** ** If the journal file is already open (as it may be in exclusive mode), ** then this function just writes a journal header to the start of the ** already open file. ** ** Whether or not the journal file is opened by this function, the ** Pager.pInJournal bitvec structure is allocated. ** ** Return SQLITE_OK if everything is successful. Otherwise, return ** SQLITE_NOMEM if the attempt to allocate Pager.pInJournal fails, or ** an IO error code if opening or writing the journal file fails. */ static int pager_open_journal(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ int nPage; /* Size of database file */ sqlite3_vfs * const pVfs = pPager->pVfs; /* Local cache of vfs pointer */ assert( pPager->state>=PAGER_RESERVED ); assert( pPager->useJournal ); assert( pPager->journalMode!=PAGER_JOURNALMODE_OFF ); assert( pPager->pInJournal==0 ); /* If already in the error state, this function is a no-op. But on ** the other hand, this routine is never called if we are already in ** an error state. */ if( NEVER(pPager->errCode) ) return pPager->errCode; testcase( pPager->dbSizeValid==0 ); rc = sqlite3PagerPagecount(pPager, &nPage); if( rc ) return rc; pPager->pInJournal = sqlite3BitvecCreate(nPage); if( pPager->pInJournal==0 ){ return SQLITE_NOMEM; } /* Open the journal file if it is not already open. */ if( !isOpen(pPager->jfd) ){ if( pPager->journalMode==PAGER_JOURNALMODE_MEMORY ){ sqlite3MemJournalOpen(pPager->jfd); }else{ const int flags = /* VFS flags to open journal file */ SQLITE_OPEN_READWRITE|SQLITE_OPEN_CREATE| (pPager->tempFile ? (SQLITE_OPEN_DELETEONCLOSE|SQLITE_OPEN_TEMP_JOURNAL): (SQLITE_OPEN_MAIN_JOURNAL) ); #ifdef SQLITE_ENABLE_ATOMIC_WRITE rc = sqlite3JournalOpen( pVfs, pPager->zJournal, pPager->jfd, flags, jrnlBufferSize(pPager) ); #else rc = sqlite3OsOpen(pVfs, pPager->zJournal, pPager->jfd, flags, 0); #endif } assert( rc!=SQLITE_OK || isOpen(pPager->jfd) ); } /* Write the first journal header to the journal file and open ** the sub-journal if necessary. */ if( rc==SQLITE_OK ){ /* TODO: Check if all of these are really required. */ pPager->dbOrigSize = pPager->dbSize; pPager->journalStarted = 0; pPager->needSync = 0; pPager->nRec = 0; pPager->journalOff = 0; pPager->setMaster = 0; pPager->journalHdr = 0; rc = writeJournalHdr(pPager); } if( rc!=SQLITE_OK ){ sqlite3BitvecDestroy(pPager->pInJournal); pPager->pInJournal = 0; } return rc; } /* ** Begin a write-transaction on the specified pager object. If a ** write-transaction has already been opened, this function is a no-op. ** ** If the exFlag argument is false, then acquire at least a RESERVED ** lock on the database file. If exFlag is true, then acquire at least ** an EXCLUSIVE lock. If such a lock is already held, no locking ** functions need be called. ** ** If this is not a temporary or in-memory file and, the journal file is ** opened if it has not been already. For a temporary file, the opening ** of the journal file is deferred until there is an actual need to ** write to the journal. TODO: Why handle temporary files differently? ** ** If the journal file is opened (or if it is already open), then a ** journal-header is written to the start of it. ** ** If the subjInMemory argument is non-zero, then any sub-journal opened ** within this transaction will be opened as an in-memory file. This ** has no effect if the sub-journal is already opened (as it may be when ** running in exclusive mode) or if the transaction does not require a ** sub-journal. If the subjInMemory argument is zero, then any required ** sub-journal is implemented in-memory if pPager is an in-memory database, ** or using a temporary file otherwise. */ int sqlite3PagerBegin(Pager *pPager, int exFlag, int subjInMemory){ int rc = SQLITE_OK; assert( pPager->state!=PAGER_UNLOCK ); pPager->subjInMemory = (u8)subjInMemory; if( pPager->state==PAGER_SHARED ){ assert( pPager->pInJournal==0 ); assert( !MEMDB && !pPager->tempFile ); if( pagerUseWal(pPager) ){ /* If the pager is configured to use locking_mode=exclusive, and an ** exclusive lock on the database is not already held, obtain it now. */ if( pPager->exclusiveMode && sqlite3WalExclusiveMode(pPager->pWal, -1) ){ rc = sqlite3OsLock(pPager->fd, EXCLUSIVE_LOCK); pPager->state = PAGER_SHARED; if( rc!=SQLITE_OK ){ return rc; } sqlite3WalExclusiveMode(pPager->pWal, 1); } /* Grab the write lock on the log file. If successful, upgrade to ** PAGER_RESERVED state. Otherwise, return an error code to the caller. ** The busy-handler is not invoked if another connection already ** holds the write-lock. If possible, the upper layer will call it. ** ** WAL mode sets Pager.state to PAGER_RESERVED when it has an open ** transaction, but never to PAGER_EXCLUSIVE. This is because in ** PAGER_EXCLUSIVE state the code to roll back savepoint transactions ** may copy data from the sub-journal into the database file as well ** as into the page cache. Which would be incorrect in WAL mode. */ rc = sqlite3WalBeginWriteTransaction(pPager->pWal); if( rc==SQLITE_OK ){ pPager->dbOrigSize = pPager->dbSize; pPager->state = PAGER_RESERVED; pPager->journalOff = 0; } assert( rc!=SQLITE_OK || pPager->state==PAGER_RESERVED ); assert( rc==SQLITE_OK || pPager->state==PAGER_SHARED ); }else{ /* Obtain a RESERVED lock on the database file. If the exFlag parameter ** is true, then immediately upgrade this to an EXCLUSIVE lock. The ** busy-handler callback can be used when upgrading to the EXCLUSIVE ** lock, but not when obtaining the RESERVED lock. */ rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK); if( rc==SQLITE_OK ){ pPager->state = PAGER_RESERVED; if( exFlag ){ rc = pager_wait_on_lock(pPager, EXCLUSIVE_LOCK); } } } /* No need to open the journal file at this time. It will be ** opened before it is written to. If we defer opening the journal, ** we might save the work of creating a file if the transaction ** ends up being a no-op. */ if( rc!=SQLITE_OK ){ assert( !pPager->dbModified ); /* Ignore any IO error that occurs within pager_end_transaction(). The ** purpose of this call is to reset the internal state of the pager ** sub-system. It doesn't matter if the journal-file is not properly ** finalized at this point (since it is not a valid journal file anyway). */ pager_end_transaction(pPager, 0); } } PAGERTRACE(("TRANSACTION %d\n", PAGERID(pPager))); return rc; } /* ** Mark a single data page as writeable. The page is written into the ** main journal or sub-journal as required. If the page is written into ** one of the journals, the corresponding bit is set in the ** Pager.pInJournal bitvec and the PagerSavepoint.pInSavepoint bitvecs ** of any open savepoints as appropriate. */ static int pager_write(PgHdr *pPg){ void *pData = pPg->pData; Pager *pPager = pPg->pPager; int rc = SQLITE_OK; /* This routine is not called unless a transaction has already been ** started. */ assert( pPager->state>=PAGER_RESERVED ); /* If an error has been previously detected, report the same error ** again. */ if( NEVER(pPager->errCode) ) return pPager->errCode; /* Higher-level routines never call this function if database is not ** writable. But check anyway, just for robustness. */ if( NEVER(pPager->readOnly) ) return SQLITE_PERM; assert( !pPager->setMaster ); CHECK_PAGE(pPg); /* Mark the page as dirty. If the page has already been written ** to the journal then we can return right away. */ sqlite3PcacheMakeDirty(pPg); if( pageInJournal(pPg) && !subjRequiresPage(pPg) ){ assert( !pagerUseWal(pPager) ); pPager->dbModified = 1; }else{ /* If we get this far, it means that the page needs to be ** written to the transaction journal or the ckeckpoint journal ** or both. ** ** Higher level routines should have already started a transaction, ** which means they have acquired the necessary locks but the rollback ** journal might not yet be open. */ assert( pPager->state>=RESERVED_LOCK ); if( pPager->pInJournal==0 && pPager->journalMode!=PAGER_JOURNALMODE_OFF && !pagerUseWal(pPager) ){ assert( pPager->useJournal ); rc = pager_open_journal(pPager); if( rc!=SQLITE_OK ) return rc; } pPager->dbModified = 1; /* The transaction journal now exists and we have a RESERVED or an ** EXCLUSIVE lock on the main database file. Write the current page to ** the transaction journal if it is not there already. */ if( !pageInJournal(pPg) && isOpen(pPager->jfd) ){ assert( !pagerUseWal(pPager) ); if( pPg->pgno<=pPager->dbOrigSize ){ u32 cksum; char *pData2; /* We should never write to the journal file the page that ** contains the database locks. The following assert verifies ** that we do not. */ assert( pPg->pgno!=PAGER_MJ_PGNO(pPager) ); assert( pPager->journalHdr <= pPager->journalOff ); CODEC2(pPager, pData, pPg->pgno, 7, return SQLITE_NOMEM, pData2); cksum = pager_cksum(pPager, (u8*)pData2); rc = write32bits(pPager->jfd, pPager->journalOff, pPg->pgno); if( rc==SQLITE_OK ){ rc = sqlite3OsWrite(pPager->jfd, pData2, pPager->pageSize, pPager->journalOff + 4); pPager->journalOff += pPager->pageSize+4; } if( rc==SQLITE_OK ){ rc = write32bits(pPager->jfd, pPager->journalOff, cksum); pPager->journalOff += 4; } IOTRACE(("JOUT %p %d %lld %d\n", pPager, pPg->pgno, pPager->journalOff, pPager->pageSize)); PAGER_INCR(sqlite3_pager_writej_count); PAGERTRACE(("JOURNAL %d page %d needSync=%d hash(%08x)\n", PAGERID(pPager), pPg->pgno, ((pPg->flags&PGHDR_NEED_SYNC)?1:0), pager_pagehash(pPg))); /* Even if an IO or diskfull error occurred while journalling the ** page in the block above, set the need-sync flag for the page. ** Otherwise, when the transaction is rolled back, the logic in ** playback_one_page() will think that the page needs to be restored ** in the database file. And if an IO error occurs while doing so, ** then corruption may follow. */ if( !pPager->noSync ){ pPg->flags |= PGHDR_NEED_SYNC; pPager->needSync = 1; } /* An error has occurred writing to the journal file. The ** transaction will be rolled back by the layer above. */ if( rc!=SQLITE_OK ){ return rc; } pPager->nRec++; assert( pPager->pInJournal!=0 ); rc = sqlite3BitvecSet(pPager->pInJournal, pPg->pgno); testcase( rc==SQLITE_NOMEM ); assert( rc==SQLITE_OK || rc==SQLITE_NOMEM ); rc |= addToSavepointBitvecs(pPager, pPg->pgno); if( rc!=SQLITE_OK ){ assert( rc==SQLITE_NOMEM ); return rc; } }else{ if( !pPager->journalStarted && !pPager->noSync ){ pPg->flags |= PGHDR_NEED_SYNC; pPager->needSync = 1; } PAGERTRACE(("APPEND %d page %d needSync=%d\n", PAGERID(pPager), pPg->pgno, ((pPg->flags&PGHDR_NEED_SYNC)?1:0))); } } /* If the statement journal is open and the page is not in it, ** then write the current page to the statement journal. Note that ** the statement journal format differs from the standard journal format ** in that it omits the checksums and the header. */ if( subjRequiresPage(pPg) ){ rc = subjournalPage(pPg); } } /* Update the database size and return. */ assert( pPager->state>=PAGER_SHARED ); if( pPager->dbSize<pPg->pgno ){ pPager->dbSize = pPg->pgno; } return rc; } /* ** Mark a data page as writeable. This routine must be called before ** making changes to a page. The caller must check the return value ** of this function and be careful not to change any page data unless ** this routine returns SQLITE_OK. ** ** The difference between this function and pager_write() is that this ** function also deals with the special case where 2 or more pages ** fit on a single disk sector. In this case all co-resident pages ** must have been written to the journal file before returning. ** ** If an error occurs, SQLITE_NOMEM or an IO error code is returned ** as appropriate. Otherwise, SQLITE_OK. */ int sqlite3PagerWrite(DbPage *pDbPage){ int rc = SQLITE_OK; PgHdr *pPg = pDbPage; Pager *pPager = pPg->pPager; Pgno nPagePerSector = (pPager->sectorSize/pPager->pageSize); if( nPagePerSector>1 ){ Pgno nPageCount; /* Total number of pages in database file */ Pgno pg1; /* First page of the sector pPg is located on. */ int nPage = 0; /* Number of pages starting at pg1 to journal */ int ii; /* Loop counter */ int needSync = 0; /* True if any page has PGHDR_NEED_SYNC */ /* Set the doNotSyncSpill flag to 1. This is because we cannot allow ** a journal header to be written between the pages journaled by ** this function. */ assert( !MEMDB ); assert( pPager->doNotSyncSpill==0 ); pPager->doNotSyncSpill++; /* This trick assumes that both the page-size and sector-size are ** an integer power of 2. It sets variable pg1 to the identifier ** of the first page of the sector pPg is located on. */ pg1 = ((pPg->pgno-1) & ~(nPagePerSector-1)) + 1; rc = sqlite3PagerPagecount(pPager, (int *)&nPageCount); if( rc==SQLITE_OK ){ if( pPg->pgno>nPageCount ){ nPage = (pPg->pgno - pg1)+1; }else if( (pg1+nPagePerSector-1)>nPageCount ){ nPage = nPageCount+1-pg1; }else{ nPage = nPagePerSector; } assert(nPage>0); assert(pg1<=pPg->pgno); assert((pg1+nPage)>pPg->pgno); } for(ii=0; ii<nPage && rc==SQLITE_OK; ii++){ Pgno pg = pg1+ii; PgHdr *pPage; if( pg==pPg->pgno || !sqlite3BitvecTest(pPager->pInJournal, pg) ){ if( pg!=PAGER_MJ_PGNO(pPager) ){ rc = sqlite3PagerGet(pPager, pg, &pPage); if( rc==SQLITE_OK ){ rc = pager_write(pPage); if( pPage->flags&PGHDR_NEED_SYNC ){ needSync = 1; assert(pPager->needSync); } sqlite3PagerUnref(pPage); } } }else if( (pPage = pager_lookup(pPager, pg))!=0 ){ if( pPage->flags&PGHDR_NEED_SYNC ){ needSync = 1; } sqlite3PagerUnref(pPage); } } /* If the PGHDR_NEED_SYNC flag is set for any of the nPage pages ** starting at pg1, then it needs to be set for all of them. Because ** writing to any of these nPage pages may damage the others, the ** journal file must contain sync()ed copies of all of them ** before any of them can be written out to the database file. */ if( rc==SQLITE_OK && needSync ){ assert( !MEMDB && pPager->noSync==0 ); for(ii=0; ii<nPage; ii++){ PgHdr *pPage = pager_lookup(pPager, pg1+ii); if( pPage ){ pPage->flags |= PGHDR_NEED_SYNC; sqlite3PagerUnref(pPage); } } assert(pPager->needSync); } assert( pPager->doNotSyncSpill==1 ); pPager->doNotSyncSpill--; }else{ rc = pager_write(pDbPage); } return rc; } /* ** Return TRUE if the page given in the argument was previously passed ** to sqlite3PagerWrite(). In other words, return TRUE if it is ok ** to change the content of the page. */ #ifndef NDEBUG int sqlite3PagerIswriteable(DbPage *pPg){ return pPg->flags&PGHDR_DIRTY; } #endif /* ** A call to this routine tells the pager that it is not necessary to ** write the information on page pPg back to the disk, even though ** that page might be marked as dirty. This happens, for example, when ** the page has been added as a leaf of the freelist and so its ** content no longer matters. ** ** The overlying software layer calls this routine when all of the data ** on the given page is unused. The pager marks the page as clean so ** that it does not get written to disk. ** ** Tests show that this optimization can quadruple the speed of large ** DELETE operations. */ void sqlite3PagerDontWrite(PgHdr *pPg){ Pager *pPager = pPg->pPager; if( (pPg->flags&PGHDR_DIRTY) && pPager->nSavepoint==0 ){ PAGERTRACE(("DONT_WRITE page %d of %d\n", pPg->pgno, PAGERID(pPager))); IOTRACE(("CLEAN %p %d\n", pPager, pPg->pgno)) pPg->flags |= PGHDR_DONT_WRITE; #ifdef SQLITE_CHECK_PAGES pPg->pageHash = pager_pagehash(pPg); #endif } } /* ** This routine is called to increment the value of the database file ** change-counter, stored as a 4-byte big-endian integer starting at ** byte offset 24 of the pager file. ** ** If the isDirectMode flag is zero, then this is done by calling ** sqlite3PagerWrite() on page 1, then modifying the contents of the ** page data. In this case the file will be updated when the current ** transaction is committed. ** ** The isDirectMode flag may only be non-zero if the library was compiled ** with the SQLITE_ENABLE_ATOMIC_WRITE macro defined. In this case, ** if isDirect is non-zero, then the database file is updated directly ** by writing an updated version of page 1 using a call to the ** sqlite3OsWrite() function. */ static int pager_incr_changecounter(Pager *pPager, int isDirectMode){ int rc = SQLITE_OK; /* Declare and initialize constant integer 'isDirect'. If the ** atomic-write optimization is enabled in this build, then isDirect ** is initialized to the value passed as the isDirectMode parameter ** to this function. Otherwise, it is always set to zero. ** ** The idea is that if the atomic-write optimization is not ** enabled at compile time, the compiler can omit the tests of ** 'isDirect' below, as well as the block enclosed in the ** "if( isDirect )" condition. */ #ifndef SQLITE_ENABLE_ATOMIC_WRITE # define DIRECT_MODE 0 assert( isDirectMode==0 ); UNUSED_PARAMETER(isDirectMode); #else # define DIRECT_MODE isDirectMode #endif assert( pPager->state>=PAGER_RESERVED ); if( !pPager->changeCountDone && pPager->dbSize>0 ){ PgHdr *pPgHdr; /* Reference to page 1 */ u32 change_counter; /* Initial value of change-counter field */ assert( !pPager->tempFile && isOpen(pPager->fd) ); /* Open page 1 of the file for writing. */ rc = sqlite3PagerGet(pPager, 1, &pPgHdr); assert( pPgHdr==0 || rc==SQLITE_OK ); /* If page one was fetched successfully, and this function is not ** operating in direct-mode, make page 1 writable. When not in ** direct mode, page 1 is always held in cache and hence the PagerGet() ** above is always successful - hence the ALWAYS on rc==SQLITE_OK. */ if( !DIRECT_MODE && ALWAYS(rc==SQLITE_OK) ){ rc = sqlite3PagerWrite(pPgHdr); } if( rc==SQLITE_OK ){ /* Increment the value just read and write it back to byte 24. */ change_counter = sqlite3Get4byte((u8*)pPager->dbFileVers); change_counter++; put32bits(((char*)pPgHdr->pData)+24, change_counter); /* Also store the SQLite version number in bytes 96..99 and in ** bytes 92..95 store the change counter for which the version number ** is valid. */ put32bits(((char*)pPgHdr->pData)+92, change_counter); put32bits(((char*)pPgHdr->pData)+96, SQLITE_VERSION_NUMBER); /* If running in direct mode, write the contents of page 1 to the file. */ if( DIRECT_MODE ){ const void *zBuf; assert( pPager->dbFileSize>0 ); CODEC2(pPager, pPgHdr->pData, 1, 6, rc=SQLITE_NOMEM, zBuf); if( rc==SQLITE_OK ){ rc = sqlite3OsWrite(pPager->fd, zBuf, pPager->pageSize, 0); } if( rc==SQLITE_OK ){ pPager->changeCountDone = 1; } }else{ pPager->changeCountDone = 1; } } /* Release the page reference. */ sqlite3PagerUnref(pPgHdr); } return rc; } /* ** Sync the pager file to disk. This is a no-op for in-memory files ** or pages with the Pager.noSync flag set. ** ** If successful, or called on a pager for which it is a no-op, this ** function returns SQLITE_OK. Otherwise, an IO error code is returned. */ int sqlite3PagerSync(Pager *pPager){ int rc; /* Return code */ assert( !MEMDB ); if( pPager->noSync ){ rc = SQLITE_OK; }else{ rc = sqlite3OsSync(pPager->fd, pPager->sync_flags); } return rc; } /* ** Sync the database file for the pager pPager. zMaster points to the name ** of a master journal file that should be written into the individual ** journal file. zMaster may be NULL, which is interpreted as no master ** journal (a single database transaction). ** ** This routine ensures that: ** ** * The database file change-counter is updated, ** * the journal is synced (unless the atomic-write optimization is used), ** * all dirty pages are written to the database file, ** * the database file is truncated (if required), and ** * the database file synced. ** ** The only thing that remains to commit the transaction is to finalize ** (delete, truncate or zero the first part of) the journal file (or ** delete the master journal file if specified). ** ** Note that if zMaster==NULL, this does not overwrite a previous value ** passed to an sqlite3PagerCommitPhaseOne() call. ** ** If the final parameter - noSync - is true, then the database file itself ** is not synced. The caller must call sqlite3PagerSync() directly to ** sync the database file before calling CommitPhaseTwo() to delete the ** journal file in this case. */ int sqlite3PagerCommitPhaseOne( Pager *pPager, /* Pager object */ const char *zMaster, /* If not NULL, the master journal name */ int noSync /* True to omit the xSync on the db file */ ){ int rc = SQLITE_OK; /* Return code */ /* The dbOrigSize is never set if journal_mode=OFF */ assert( pPager->journalMode!=PAGER_JOURNALMODE_OFF || pPager->dbOrigSize==0 ); /* If a prior error occurred, report that error again. */ if( pPager->errCode ) return pPager->errCode; PAGERTRACE(("DATABASE SYNC: File=%s zMaster=%s nSize=%d\n", pPager->zFilename, zMaster, pPager->dbSize)); if( MEMDB && pPager->dbModified ){ /* If this is an in-memory db, or no pages have been written to, or this ** function has already been called, it is mostly a no-op. However, any ** backup in progress needs to be restarted. */ sqlite3BackupRestart(pPager->pBackup); }else if( pPager->state!=PAGER_SYNCED && pPager->dbModified ){ if( pagerUseWal(pPager) ){ PgHdr *pList = sqlite3PcacheDirtyList(pPager->pPCache); if( pList ){ rc = pagerWalFrames(pPager, pList, pPager->dbSize, 1, (pPager->fullSync ? pPager->sync_flags : 0) ); } if( rc==SQLITE_OK ){ sqlite3PcacheCleanAll(pPager->pPCache); } }else{ /* The following block updates the change-counter. Exactly how it ** does this depends on whether or not the atomic-update optimization ** was enabled at compile time, and if this transaction meets the ** runtime criteria to use the operation: ** ** * The file-system supports the atomic-write property for ** blocks of size page-size, and ** * This commit is not part of a multi-file transaction, and ** * Exactly one page has been modified and store in the journal file. ** ** If the optimization was not enabled at compile time, then the ** pager_incr_changecounter() function is called to update the change ** counter in 'indirect-mode'. If the optimization is compiled in but ** is not applicable to this transaction, call sqlite3JournalCreate() ** to make sure the journal file has actually been created, then call ** pager_incr_changecounter() to update the change-counter in indirect ** mode. ** ** Otherwise, if the optimization is both enabled and applicable, ** then call pager_incr_changecounter() to update the change-counter ** in 'direct' mode. In this case the journal file will never be ** created for this transaction. */ #ifdef SQLITE_ENABLE_ATOMIC_WRITE PgHdr *pPg; assert( isOpen(pPager->jfd) || pPager->journalMode==PAGER_JOURNALMODE_OFF ); if( !zMaster && isOpen(pPager->jfd) && pPager->journalOff==jrnlBufferSize(pPager) && pPager->dbSize>=pPager->dbFileSize && (0==(pPg = sqlite3PcacheDirtyList(pPager->pPCache)) || 0==pPg->pDirty) ){ /* Update the db file change counter via the direct-write method. The ** following call will modify the in-memory representation of page 1 ** to include the updated change counter and then write page 1 ** directly to the database file. Because of the atomic-write ** property of the host file-system, this is safe. */ rc = pager_incr_changecounter(pPager, 1); }else{ rc = sqlite3JournalCreate(pPager->jfd); if( rc==SQLITE_OK ){ rc = pager_incr_changecounter(pPager, 0); } } #else rc = pager_incr_changecounter(pPager, 0); #endif if( rc!=SQLITE_OK ) goto commit_phase_one_exit; /* If this transaction has made the database smaller, then all pages ** being discarded by the truncation must be written to the journal ** file. This can only happen in auto-vacuum mode. ** ** Before reading the pages with page numbers larger than the ** current value of Pager.dbSize, set dbSize back to the value ** that it took at the start of the transaction. Otherwise, the ** calls to sqlite3PagerGet() return zeroed pages instead of ** reading data from the database file. ** ** When journal_mode==OFF the dbOrigSize is always zero, so this ** block never runs if journal_mode=OFF. */ #ifndef SQLITE_OMIT_AUTOVACUUM if( pPager->dbSize<pPager->dbOrigSize && ALWAYS(pPager->journalMode!=PAGER_JOURNALMODE_OFF) ){ Pgno i; /* Iterator variable */ const Pgno iSkip = PAGER_MJ_PGNO(pPager); /* Pending lock page */ const Pgno dbSize = pPager->dbSize; /* Database image size */ pPager->dbSize = pPager->dbOrigSize; for( i=dbSize+1; i<=pPager->dbOrigSize; i++ ){ if( !sqlite3BitvecTest(pPager->pInJournal, i) && i!=iSkip ){ PgHdr *pPage; /* Page to journal */ rc = sqlite3PagerGet(pPager, i, &pPage); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; rc = sqlite3PagerWrite(pPage); sqlite3PagerUnref(pPage); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; } } pPager->dbSize = dbSize; } #endif /* Write the master journal name into the journal file. If a master ** journal file name has already been written to the journal file, ** or if zMaster is NULL (no master journal), then this call is a no-op. */ rc = writeMasterJournal(pPager, zMaster); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; /* Sync the journal file. If the atomic-update optimization is being ** used, this call will not create the journal file or perform any ** real IO. */ rc = syncJournal(pPager); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; /* Write all dirty pages to the database file. */ rc = pager_write_pagelist(sqlite3PcacheDirtyList(pPager->pPCache)); if( rc!=SQLITE_OK ){ assert( rc!=SQLITE_IOERR_BLOCKED ); goto commit_phase_one_exit; } sqlite3PcacheCleanAll(pPager->pPCache); /* If the file on disk is not the same size as the database image, ** then use pager_truncate to grow or shrink the file here. */ if( pPager->dbSize!=pPager->dbFileSize ){ Pgno nNew = pPager->dbSize - (pPager->dbSize==PAGER_MJ_PGNO(pPager)); assert( pPager->state>=PAGER_EXCLUSIVE ); rc = pager_truncate(pPager, nNew); if( rc!=SQLITE_OK ) goto commit_phase_one_exit; } /* Finally, sync the database file. */ if( !pPager->noSync && !noSync ){ rc = sqlite3OsSync(pPager->fd, pPager->sync_flags); } IOTRACE(("DBSYNC %p\n", pPager)) } pPager->state = PAGER_SYNCED; } commit_phase_one_exit: return rc; } /* ** When this function is called, the database file has been completely ** updated to reflect the changes made by the current transaction and ** synced to disk. The journal file still exists in the file-system ** though, and if a failure occurs at this point it will eventually ** be used as a hot-journal and the current transaction rolled back. ** ** This function finalizes the journal file, either by deleting, ** truncating or partially zeroing it, so that it cannot be used ** for hot-journal rollback. Once this is done the transaction is ** irrevocably committed. ** ** If an error occurs, an IO error code is returned and the pager ** moves into the error state. Otherwise, SQLITE_OK is returned. */ int sqlite3PagerCommitPhaseTwo(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ /* This routine should not be called if a prior error has occurred. ** But if (due to a coding error elsewhere in the system) it does get ** called, just return the same error code without doing anything. */ if( NEVER(pPager->errCode) ) return pPager->errCode; /* This function should not be called if the pager is not in at least ** PAGER_RESERVED state. **FIXME**: Make it so that this test always ** fails - make it so that we never reach this point if we do not hold ** all necessary locks. */ if( NEVER(pPager->state<PAGER_RESERVED) ) return SQLITE_ERROR; /* An optimization. If the database was not actually modified during ** this transaction, the pager is running in exclusive-mode and is ** using persistent journals, then this function is a no-op. ** ** The start of the journal file currently contains a single journal ** header with the nRec field set to 0. If such a journal is used as ** a hot-journal during hot-journal rollback, 0 changes will be made ** to the database file. So there is no need to zero the journal ** header. Since the pager is in exclusive mode, there is no need ** to drop any locks either. */ if( pPager->dbModified==0 && pPager->exclusiveMode && pPager->journalMode==PAGER_JOURNALMODE_PERSIST ){ assert( pPager->journalOff==JOURNAL_HDR_SZ(pPager) || !pPager->journalOff ); return SQLITE_OK; } PAGERTRACE(("COMMIT %d\n", PAGERID(pPager))); assert( pPager->state==PAGER_SYNCED || MEMDB || !pPager->dbModified ); rc = pager_end_transaction(pPager, pPager->setMaster); return pager_error(pPager, rc); } /* ** Rollback all changes. The database falls back to PAGER_SHARED mode. ** ** This function performs two tasks: ** ** 1) It rolls back the journal file, restoring all database file and ** in-memory cache pages to the state they were in when the transaction ** was opened, and ** 2) It finalizes the journal file, so that it is not used for hot ** rollback at any point in the future. ** ** subject to the following qualifications: ** ** * If the journal file is not yet open when this function is called, ** then only (2) is performed. In this case there is no journal file ** to roll back. ** ** * If in an error state other than SQLITE_FULL, then task (1) is ** performed. If successful, task (2). Regardless of the outcome ** of either, the error state error code is returned to the caller ** (i.e. either SQLITE_IOERR or SQLITE_CORRUPT). ** ** * If the pager is in PAGER_RESERVED state, then attempt (1). Whether ** or not (1) is successful, also attempt (2). If successful, return ** SQLITE_OK. Otherwise, enter the error state and return the first ** error code encountered. ** ** In this case there is no chance that the database was written to. ** So is safe to finalize the journal file even if the playback ** (operation 1) failed. However the pager must enter the error state ** as the contents of the in-memory cache are now suspect. ** ** * Finally, if in PAGER_EXCLUSIVE state, then attempt (1). Only ** attempt (2) if (1) is successful. Return SQLITE_OK if successful, ** otherwise enter the error state and return the error code from the ** failing operation. ** ** In this case the database file may have been written to. So if the ** playback operation did not succeed it would not be safe to finalize ** the journal file. It needs to be left in the file-system so that ** some other process can use it to restore the database state (by ** hot-journal rollback). */ int sqlite3PagerRollback(Pager *pPager){ int rc = SQLITE_OK; /* Return code */ PAGERTRACE(("ROLLBACK %d\n", PAGERID(pPager))); if( pagerUseWal(pPager) ){ int rc2; rc = sqlite3PagerSavepoint(pPager, SAVEPOINT_ROLLBACK, -1); rc2 = pager_end_transaction(pPager, pPager->setMaster); if( rc==SQLITE_OK ) rc = rc2; rc = pager_error(pPager, rc); }else if( !pPager->dbModified || !isOpen(pPager->jfd) ){ rc = pager_end_transaction(pPager, pPager->setMaster); }else if( pPager->errCode && pPager->errCode!=SQLITE_FULL ){ if( pPager->state>=PAGER_EXCLUSIVE ){ pager_playback(pPager, 0); } rc = pPager->errCode; }else{ if( pPager->state==PAGER_RESERVED ){ int rc2; rc = pager_playback(pPager, 0); rc2 = pager_end_transaction(pPager, pPager->setMaster); if( rc==SQLITE_OK ){ rc = rc2; } }else{ rc = pager_playback(pPager, 0); } if( !MEMDB ){ pPager->dbSizeValid = 0; } /* If an error occurs during a ROLLBACK, we can no longer trust the pager ** cache. So call pager_error() on the way out to make any error ** persistent. */ rc = pager_error(pPager, rc); } return rc; } /* ** Return TRUE if the database file is opened read-only. Return FALSE ** if the database is (in theory) writable. */ u8 sqlite3PagerIsreadonly(Pager *pPager){ return pPager->readOnly; } /* ** Return the number of references to the pager. */ int sqlite3PagerRefcount(Pager *pPager){ return sqlite3PcacheRefCount(pPager->pPCache); } /* ** Return the approximate number of bytes of memory currently ** used by the pager and its associated cache. */ int sqlite3PagerMemUsed(Pager *pPager){ int perPageSize = pPager->pageSize + pPager->nExtra + 20; return perPageSize*sqlite3PcachePagecount(pPager->pPCache) + sqlite3MallocSize(pPager); } /* ** Return the number of references to the specified page. */ int sqlite3PagerPageRefcount(DbPage *pPage){ return sqlite3PcachePageRefcount(pPage); } #ifdef SQLITE_TEST /* ** This routine is used for testing and analysis only. */ int *sqlite3PagerStats(Pager *pPager){ static int a[11]; a[0] = sqlite3PcacheRefCount(pPager->pPCache); a[1] = sqlite3PcachePagecount(pPager->pPCache); a[2] = sqlite3PcacheGetCachesize(pPager->pPCache); a[3] = pPager->dbSizeValid ? (int) pPager->dbSize : -1; a[4] = pPager->state; a[5] = pPager->errCode; a[6] = pPager->nHit; a[7] = pPager->nMiss; a[8] = 0; /* Used to be pPager->nOvfl */ a[9] = pPager->nRead; a[10] = pPager->nWrite; return a; } #endif /* ** Return true if this is an in-memory pager. */ int sqlite3PagerIsMemdb(Pager *pPager){ return MEMDB; } /* ** Check that there are at least nSavepoint savepoints open. If there are ** currently less than nSavepoints open, then open one or more savepoints ** to make up the difference. If the number of savepoints is already ** equal to nSavepoint, then this function is a no-op. ** ** If a memory allocation fails, SQLITE_NOMEM is returned. If an error ** occurs while opening the sub-journal file, then an IO error code is ** returned. Otherwise, SQLITE_OK. */ int sqlite3PagerOpenSavepoint(Pager *pPager, int nSavepoint){ int rc = SQLITE_OK; /* Return code */ int nCurrent = pPager->nSavepoint; /* Current number of savepoints */ if( nSavepoint>nCurrent && pPager->useJournal ){ int ii; /* Iterator variable */ PagerSavepoint *aNew; /* New Pager.aSavepoint array */ int nPage; /* Size of database file */ rc = sqlite3PagerPagecount(pPager, &nPage); if( rc ) return rc; /* Grow the Pager.aSavepoint array using realloc(). Return SQLITE_NOMEM ** if the allocation fails. Otherwise, zero the new portion in case a ** malloc failure occurs while populating it in the for(...) loop below. */ aNew = (PagerSavepoint *)sqlite3Realloc( pPager->aSavepoint, sizeof(PagerSavepoint)*nSavepoint ); if( !aNew ){ return SQLITE_NOMEM; } memset(&aNew[nCurrent], 0, (nSavepoint-nCurrent) * sizeof(PagerSavepoint)); pPager->aSavepoint = aNew; /* Populate the PagerSavepoint structures just allocated. */ for(ii=nCurrent; ii<nSavepoint; ii++){ aNew[ii].nOrig = nPage; if( isOpen(pPager->jfd) && pPager->journalOff>0 ){ aNew[ii].iOffset = pPager->journalOff; }else{ aNew[ii].iOffset = JOURNAL_HDR_SZ(pPager); } aNew[ii].iSubRec = pPager->nSubRec; aNew[ii].pInSavepoint = sqlite3BitvecCreate(nPage); if( !aNew[ii].pInSavepoint ){ return SQLITE_NOMEM; } if( pagerUseWal(pPager) ){ sqlite3WalSavepoint(pPager->pWal, aNew[ii].aWalData); } pPager->nSavepoint = ii+1; } assert( pPager->nSavepoint==nSavepoint ); assertTruncateConstraint(pPager); } return rc; } /* ** This function is called to rollback or release (commit) a savepoint. ** The savepoint to release or rollback need not be the most recently ** created savepoint. ** ** Parameter op is always either SAVEPOINT_ROLLBACK or SAVEPOINT_RELEASE. ** If it is SAVEPOINT_RELEASE, then release and destroy the savepoint with ** index iSavepoint. If it is SAVEPOINT_ROLLBACK, then rollback all changes ** that have occurred since the specified savepoint was created. ** ** The savepoint to rollback or release is identified by parameter ** iSavepoint. A value of 0 means to operate on the outermost savepoint ** (the first created). A value of (Pager.nSavepoint-1) means operate ** on the most recently created savepoint. If iSavepoint is greater than ** (Pager.nSavepoint-1), then this function is a no-op. ** ** If a negative value is passed to this function, then the current ** transaction is rolled back. This is different to calling ** sqlite3PagerRollback() because this function does not terminate ** the transaction or unlock the database, it just restores the ** contents of the database to its original state. ** ** In any case, all savepoints with an index greater than iSavepoint ** are destroyed. If this is a release operation (op==SAVEPOINT_RELEASE), ** then savepoint iSavepoint is also destroyed. ** ** This function may return SQLITE_NOMEM if a memory allocation fails, ** or an IO error code if an IO error occurs while rolling back a ** savepoint. If no errors occur, SQLITE_OK is returned. */ int sqlite3PagerSavepoint(Pager *pPager, int op, int iSavepoint){ int rc = SQLITE_OK; assert( op==SAVEPOINT_RELEASE || op==SAVEPOINT_ROLLBACK ); assert( iSavepoint>=0 || op==SAVEPOINT_ROLLBACK ); if( iSavepoint<pPager->nSavepoint ){ int ii; /* Iterator variable */ int nNew; /* Number of remaining savepoints after this op. */ /* Figure out how many savepoints will still be active after this ** operation. Store this value in nNew. Then free resources associated ** with any savepoints that are destroyed by this operation. */ nNew = iSavepoint + (( op==SAVEPOINT_RELEASE ) ? 0 : 1); for(ii=nNew; ii<pPager->nSavepoint; ii++){ sqlite3BitvecDestroy(pPager->aSavepoint[ii].pInSavepoint); } pPager->nSavepoint = nNew; /* If this is a release of the outermost savepoint, truncate ** the sub-journal to zero bytes in size. */ if( op==SAVEPOINT_RELEASE ){ if( nNew==0 && isOpen(pPager->sjfd) ){ /* Only truncate if it is an in-memory sub-journal. */ if( sqlite3IsMemJournal(pPager->sjfd) ){ rc = sqlite3OsTruncate(pPager->sjfd, 0); assert( rc==SQLITE_OK ); } pPager->nSubRec = 0; } } /* Else this is a rollback operation, playback the specified savepoint. ** If this is a temp-file, it is possible that the journal file has ** not yet been opened. In this case there have been no changes to ** the database file, so the playback operation can be skipped. */ else if( pagerUseWal(pPager) || isOpen(pPager->jfd) ){ PagerSavepoint *pSavepoint = (nNew==0)?0:&pPager->aSavepoint[nNew-1]; rc = pagerPlaybackSavepoint(pPager, pSavepoint); assert(rc!=SQLITE_DONE); } } return rc; } /* ** Return the full pathname of the database file. */ const char *sqlite3PagerFilename(Pager *pPager){ return pPager->zFilename; } /* ** Return the VFS structure for the pager. */ const sqlite3_vfs *sqlite3PagerVfs(Pager *pPager){ return pPager->pVfs; } /* ** Return the file handle for the database file associated ** with the pager. This might return NULL if the file has ** not yet been opened. */ sqlite3_file *sqlite3PagerFile(Pager *pPager){ return pPager->fd; } /* ** Return the full pathname of the journal file. */ const char *sqlite3PagerJournalname(Pager *pPager){ return pPager->zJournal; } /* ** Return true if fsync() calls are disabled for this pager. Return FALSE ** if fsync()s are executed normally. */ int sqlite3PagerNosync(Pager *pPager){ return pPager->noSync; } #ifdef SQLITE_HAS_CODEC /* ** Set or retrieve the codec for this pager */ void sqlite3PagerSetCodec( Pager *pPager, void *(*xCodec)(void*,void*,Pgno,int), void (*xCodecSizeChng)(void*,int,int), void (*xCodecFree)(void*), void *pCodec ){ if( pPager->xCodecFree ) pPager->xCodecFree(pPager->pCodec); pPager->xCodec = pPager->memDb ? 0 : xCodec; pPager->xCodecSizeChng = xCodecSizeChng; pPager->xCodecFree = xCodecFree; pPager->pCodec = pCodec; pagerReportSize(pPager); } void *sqlite3PagerGetCodec(Pager *pPager){ return pPager->pCodec; } #endif #ifndef SQLITE_OMIT_AUTOVACUUM /* ** Move the page pPg to location pgno in the file. ** ** There must be no references to the page previously located at ** pgno (which we call pPgOld) though that page is allowed to be ** in cache. If the page previously located at pgno is not already ** in the rollback journal, it is not put there by by this routine. ** ** References to the page pPg remain valid. Updating any ** meta-data associated with pPg (i.e. data stored in the nExtra bytes ** allocated along with the page) is the responsibility of the caller. ** ** A transaction must be active when this routine is called. It used to be ** required that a statement transaction was not active, but this restriction ** has been removed (CREATE INDEX needs to move a page when a statement ** transaction is active). ** ** If the fourth argument, isCommit, is non-zero, then this page is being ** moved as part of a database reorganization just before the transaction ** is being committed. In this case, it is guaranteed that the database page ** pPg refers to will not be written to again within this transaction. ** ** This function may return SQLITE_NOMEM or an IO error code if an error ** occurs. Otherwise, it returns SQLITE_OK. */ int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){ PgHdr *pPgOld; /* The page being overwritten. */ Pgno needSyncPgno = 0; /* Old value of pPg->pgno, if sync is required */ int rc; /* Return code */ Pgno origPgno; /* The original page number */ assert( pPg->nRef>0 ); /* In order to be able to rollback, an in-memory database must journal ** the page we are moving from. */ if( MEMDB ){ rc = sqlite3PagerWrite(pPg); if( rc ) return rc; } /* If the page being moved is dirty and has not been saved by the latest ** savepoint, then save the current contents of the page into the ** sub-journal now. This is required to handle the following scenario: ** ** BEGIN; ** <journal page X, then modify it in memory> ** SAVEPOINT one; ** <Move page X to location Y> ** ROLLBACK TO one; ** ** If page X were not written to the sub-journal here, it would not ** be possible to restore its contents when the "ROLLBACK TO one" ** statement were is processed. ** ** subjournalPage() may need to allocate space to store pPg->pgno into ** one or more savepoint bitvecs. This is the reason this function ** may return SQLITE_NOMEM. */ if( pPg->flags&PGHDR_DIRTY && subjRequiresPage(pPg) && SQLITE_OK!=(rc = subjournalPage(pPg)) ){ return rc; } PAGERTRACE(("MOVE %d page %d (needSync=%d) moves to %d\n", PAGERID(pPager), pPg->pgno, (pPg->flags&PGHDR_NEED_SYNC)?1:0, pgno)); IOTRACE(("MOVE %p %d %d\n", pPager, pPg->pgno, pgno)) /* If the journal needs to be sync()ed before page pPg->pgno can ** be written to, store pPg->pgno in local variable needSyncPgno. ** ** If the isCommit flag is set, there is no need to remember that ** the journal needs to be sync()ed before database page pPg->pgno ** can be written to. The caller has already promised not to write to it. */ if( (pPg->flags&PGHDR_NEED_SYNC) && !isCommit ){ needSyncPgno = pPg->pgno; assert( pageInJournal(pPg) || pPg->pgno>pPager->dbOrigSize ); assert( pPg->flags&PGHDR_DIRTY ); assert( pPager->needSync ); } /* If the cache contains a page with page-number pgno, remove it ** from its hash chain. Also, if the PgHdr.needSync was set for ** page pgno before the 'move' operation, it needs to be retained ** for the page moved there. */ pPg->flags &= ~PGHDR_NEED_SYNC; pPgOld = pager_lookup(pPager, pgno); assert( !pPgOld || pPgOld->nRef==1 ); if( pPgOld ){ pPg->flags |= (pPgOld->flags&PGHDR_NEED_SYNC); if( MEMDB ){ /* Do not discard pages from an in-memory database since we might ** need to rollback later. Just move the page out of the way. */ assert( pPager->dbSizeValid ); sqlite3PcacheMove(pPgOld, pPager->dbSize+1); }else{ sqlite3PcacheDrop(pPgOld); } } origPgno = pPg->pgno; sqlite3PcacheMove(pPg, pgno); sqlite3PcacheMakeDirty(pPg); pPager->dbModified = 1; if( needSyncPgno ){ /* If needSyncPgno is non-zero, then the journal file needs to be ** sync()ed before any data is written to database file page needSyncPgno. ** Currently, no such page exists in the page-cache and the ** "is journaled" bitvec flag has been set. This needs to be remedied by ** loading the page into the pager-cache and setting the PgHdr.needSync ** flag. ** ** If the attempt to load the page into the page-cache fails, (due ** to a malloc() or IO failure), clear the bit in the pInJournal[] ** array. Otherwise, if the page is loaded and written again in ** this transaction, it may be written to the database file before ** it is synced into the journal file. This way, it may end up in ** the journal file twice, but that is not a problem. ** ** The sqlite3PagerGet() call may cause the journal to sync. So make ** sure the Pager.needSync flag is set too. */ PgHdr *pPgHdr; assert( pPager->needSync ); rc = sqlite3PagerGet(pPager, needSyncPgno, &pPgHdr); if( rc!=SQLITE_OK ){ if( needSyncPgno<=pPager->dbOrigSize ){ assert( pPager->pTmpSpace!=0 ); sqlite3BitvecClear(pPager->pInJournal, needSyncPgno, pPager->pTmpSpace); } return rc; } pPager->needSync = 1; assert( pPager->noSync==0 && !MEMDB ); pPgHdr->flags |= PGHDR_NEED_SYNC; sqlite3PcacheMakeDirty(pPgHdr); sqlite3PagerUnref(pPgHdr); } /* ** For an in-memory database, make sure the original page continues ** to exist, in case the transaction needs to roll back. Use pPgOld ** as the original page since it has already been allocated. */ if( MEMDB ){ sqlite3PcacheMove(pPgOld, origPgno); sqlite3PagerUnref(pPgOld); } return SQLITE_OK; } #endif /* ** Return a pointer to the data for the specified page. */ void *sqlite3PagerGetData(DbPage *pPg){ assert( pPg->nRef>0 || pPg->pPager->memDb ); return pPg->pData; } /* ** Return a pointer to the Pager.nExtra bytes of "extra" space ** allocated along with the specified page. */ void *sqlite3PagerGetExtra(DbPage *pPg){ return pPg->pExtra; } /* ** Get/set the locking-mode for this pager. Parameter eMode must be one ** of PAGER_LOCKINGMODE_QUERY, PAGER_LOCKINGMODE_NORMAL or ** PAGER_LOCKINGMODE_EXCLUSIVE. If the parameter is not _QUERY, then ** the locking-mode is set to the value specified. ** ** The returned value is either PAGER_LOCKINGMODE_NORMAL or ** PAGER_LOCKINGMODE_EXCLUSIVE, indicating the current (possibly updated) ** locking-mode. */ int sqlite3PagerLockingMode(Pager *pPager, int eMode){ assert( eMode==PAGER_LOCKINGMODE_QUERY || eMode==PAGER_LOCKINGMODE_NORMAL || eMode==PAGER_LOCKINGMODE_EXCLUSIVE ); assert( PAGER_LOCKINGMODE_QUERY<0 ); assert( PAGER_LOCKINGMODE_NORMAL>=0 && PAGER_LOCKINGMODE_EXCLUSIVE>=0 ); if( eMode>=0 && !pPager->tempFile ){ pPager->exclusiveMode = (u8)eMode; } return (int)pPager->exclusiveMode; } /* ** Set the journal-mode for this pager. Parameter eMode must be one of: ** ** PAGER_JOURNALMODE_DELETE ** PAGER_JOURNALMODE_TRUNCATE ** PAGER_JOURNALMODE_PERSIST ** PAGER_JOURNALMODE_OFF ** PAGER_JOURNALMODE_MEMORY ** PAGER_JOURNALMODE_WAL ** ** The journalmode is set to the value specified if the change is allowed. ** The change may be disallowed for the following reasons: ** ** * An in-memory database can only have its journal_mode set to _OFF ** or _MEMORY. ** ** * Temporary databases cannot have _WAL journalmode. ** ** The returned indicate the current (possibly updated) journal-mode. */ int sqlite3PagerSetJournalMode(Pager *pPager, int eMode){ u8 eOld = pPager->journalMode; /* Prior journalmode */ /* The eMode parameter is always valid */ assert( eMode==PAGER_JOURNALMODE_DELETE || eMode==PAGER_JOURNALMODE_TRUNCATE || eMode==PAGER_JOURNALMODE_PERSIST || eMode==PAGER_JOURNALMODE_OFF || eMode==PAGER_JOURNALMODE_WAL || eMode==PAGER_JOURNALMODE_MEMORY ); /* Do not allow the journalmode of a TEMP database to be changed to WAL */ if( pPager->tempFile && eMode==PAGER_JOURNALMODE_WAL ){ assert( eOld!=PAGER_JOURNALMODE_WAL ); eMode = eOld; } /* Do allow the journalmode of an in-memory database to be set to ** anything other than MEMORY or OFF */ if( MEMDB ){ assert( eOld==PAGER_JOURNALMODE_MEMORY || eOld==PAGER_JOURNALMODE_OFF ); if( eMode!=PAGER_JOURNALMODE_MEMORY && eMode!=PAGER_JOURNALMODE_OFF ){ eMode = eOld; } } if( eMode!=eOld ){ /* When changing between rollback modes, close the journal file prior ** to the change. But when changing from a rollback mode to WAL, keep ** the journal open since there is a rollback-style transaction in play ** used to convert the version numbers in the btree header. */ if( isOpen(pPager->jfd) && eMode!=PAGER_JOURNALMODE_WAL ){ sqlite3OsClose(pPager->jfd); } /* Change the journal mode. */ pPager->journalMode = (u8)eMode; /* When transistioning from TRUNCATE or PERSIST to any other journal ** mode except WAL (and we are not in locking_mode=EXCLUSIVE) then ** delete the journal file. */ assert( (PAGER_JOURNALMODE_TRUNCATE & 5)==1 ); assert( (PAGER_JOURNALMODE_PERSIST & 5)==1 ); assert( (PAGER_JOURNALMODE_DELETE & 5)==0 ); assert( (PAGER_JOURNALMODE_MEMORY & 5)==4 ); assert( (PAGER_JOURNALMODE_OFF & 5)==0 ); assert( (PAGER_JOURNALMODE_WAL & 5)==5 ); assert( isOpen(pPager->fd) || pPager->exclusiveMode ); if( !pPager->exclusiveMode && (eOld & 5)==1 && (eMode & 1)==0 ){ /* In this case we would like to delete the journal file. If it is ** not possible, then that is not a problem. Deleting the journal file ** here is an optimization only. ** ** Before deleting the journal file, obtain a RESERVED lock on the ** database file. This ensures that the journal file is not deleted ** while it is in use by some other client. */ int rc = SQLITE_OK; int state = pPager->state; if( state<PAGER_SHARED ){ rc = sqlite3PagerSharedLock(pPager); } if( pPager->state==PAGER_SHARED ){ assert( rc==SQLITE_OK ); rc = sqlite3OsLock(pPager->fd, RESERVED_LOCK); } if( rc==SQLITE_OK ){ sqlite3OsDelete(pPager->pVfs, pPager->zJournal, 0); } if( rc==SQLITE_OK && state==PAGER_SHARED ){ sqlite3OsUnlock(pPager->fd, SHARED_LOCK); }else if( state==PAGER_UNLOCK ){ pager_unlock(pPager); } assert( state==pPager->state ); } } /* Return the new journal mode */ return (int)pPager->journalMode; } /* ** Return the current journal mode. */ int sqlite3PagerGetJournalMode(Pager *pPager){ return (int)pPager->journalMode; } /* ** Return TRUE if the pager is in a state where it is OK to change the ** journalmode. Journalmode changes can only happen when the database ** is unmodified. */ int sqlite3PagerOkToChangeJournalMode(Pager *pPager){ if( pPager->dbModified ) return 0; if( NEVER(isOpen(pPager->jfd) && pPager->journalOff>0) ) return 0; return 1; } /* ** Get/set the size-limit used for persistent journal files. ** ** Setting the size limit to -1 means no limit is enforced. ** An attempt to set a limit smaller than -1 is a no-op. */ i64 sqlite3PagerJournalSizeLimit(Pager *pPager, i64 iLimit){ if( iLimit>=-1 ){ pPager->journalSizeLimit = iLimit; } return pPager->journalSizeLimit; } /* ** Return a pointer to the pPager->pBackup variable. The backup module ** in backup.c maintains the content of this variable. This module ** uses it opaquely as an argument to sqlite3BackupRestart() and ** sqlite3BackupUpdate() only. */ sqlite3_backup **sqlite3PagerBackupPtr(Pager *pPager){ return &pPager->pBackup; } #ifndef SQLITE_OMIT_WAL /* ** This function is called when the user invokes "PRAGMA checkpoint". */ int sqlite3PagerCheckpoint(Pager *pPager){ int rc = SQLITE_OK; if( pPager->pWal ){ u8 *zBuf = (u8 *)pPager->pTmpSpace; rc = sqlite3WalCheckpoint(pPager->pWal, (pPager->noSync ? 0 : pPager->sync_flags), pPager->pageSize, zBuf ); } return rc; } int sqlite3PagerWalCallback(Pager *pPager){ return sqlite3WalCallback(pPager->pWal); } /* ** Return true if the underlying VFS for the given pager supports the ** primitives necessary for write-ahead logging. */ int sqlite3PagerWalSupported(Pager *pPager){ const sqlite3_io_methods *pMethods = pPager->fd->pMethods; return pMethods->iVersion>=2 && pMethods->xShmOpen!=0; } /* ** The caller must be holding a SHARED lock on the database file to call ** this function. ** ** If the pager passed as the first argument is open on a real database ** file (not a temp file or an in-memory database), and the WAL file ** is not already open, make an attempt to open it now. If successful, ** return SQLITE_OK. If an error occurs or the VFS used by the pager does ** not support the xShmXXX() methods, return an error code. *pisOpen is ** not modified in either case. ** ** If the pager is open on a temp-file (or in-memory database), or if ** the WAL file is already open, set *pisOpen to 1 and return SQLITE_OK ** without doing anything. */ int sqlite3PagerOpenWal( Pager *pPager, /* Pager object */ int *pisOpen /* OUT: Set to true if call is a no-op */ ){ int rc = SQLITE_OK; /* Return code */ assert( pPager->state>=PAGER_SHARED ); assert( (pisOpen==0 && !pPager->tempFile && !pPager->pWal) || *pisOpen==0 ); if( !pPager->tempFile && !pPager->pWal ){ if( !sqlite3PagerWalSupported(pPager) ) return SQLITE_CANTOPEN; /* Open the connection to the log file. If this operation fails, ** (e.g. due to malloc() failure), unlock the database file and ** return an error code. */ rc = sqlite3WalOpen(pPager->pVfs, pPager->fd, pPager->zFilename, &pPager->pWal); if( rc==SQLITE_OK ){ pPager->journalMode = PAGER_JOURNALMODE_WAL; } }else{ *pisOpen = 1; } return rc; } /* ** This function is called to close the connection to the log file prior ** to switching from WAL to rollback mode. ** ** Before closing the log file, this function attempts to take an ** EXCLUSIVE lock on the database file. If this cannot be obtained, an ** error (SQLITE_BUSY) is returned and the log connection is not closed. ** If successful, the EXCLUSIVE lock is not released before returning. */ int sqlite3PagerCloseWal(Pager *pPager){ int rc = SQLITE_OK; assert( pPager->journalMode==PAGER_JOURNALMODE_WAL ); /* If the log file is not already open, but does exist in the file-system, ** it may need to be checkpointed before the connection can switch to ** rollback mode. Open it now so this can happen. */ if( !pPager->pWal ){ int logexists = 0; rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_SHARED); if( rc==SQLITE_OK ){ rc = pagerCheckForOrDeleteWAL(pPager, &logexists); } if( rc==SQLITE_OK && logexists ){ rc = sqlite3WalOpen(pPager->pVfs, pPager->fd, pPager->zFilename, &pPager->pWal); } } /* Checkpoint and close the log. Because an EXCLUSIVE lock is held on ** the database file, the log and log-summary files will be deleted. */ if( rc==SQLITE_OK && pPager->pWal ){ rc = sqlite3OsLock(pPager->fd, SQLITE_LOCK_EXCLUSIVE); if( rc==SQLITE_OK ){ rc = sqlite3WalClose(pPager->pWal, (pPager->noSync ? 0 : pPager->sync_flags), pPager->pageSize, (u8*)pPager->pTmpSpace ); pPager->pWal = 0; }else{ /* If we cannot get an EXCLUSIVE lock, downgrade the PENDING lock ** that we did get back to SHARED. */ sqlite3OsUnlock(pPager->fd, SQLITE_LOCK_SHARED); } } return rc; } #ifdef SQLITE_HAS_CODEC /* ** This function is called by the wal module when writing page content ** into the log file. ** ** This function returns a pointer to a buffer containing the encrypted ** page content. If a malloc fails, this function may return NULL. */ void *sqlite3PagerCodec(PgHdr *pPg){ void *aData = 0; CODEC2(pPg->pPager, pPg->pData, pPg->pgno, 6, return 0, aData); return aData; } #endif /* SQLITE_HAS_CODEC */ #endif /* !SQLITE_OMIT_WAL */ #endif /* SQLITE_OMIT_DISKIO */ |