/ Check-in [5a814202]
Login

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Do not use the page containing locks for anything to avoid problems with the manditory file locking on windows. (CVS 1595)
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 5a814202777f381caf5337b37e11c9ab8b8f554a
User & Date: drh 2004-06-15 01:40:29
Context
2004-06-15
02:13
Update comments in btree.c. No changes to code. (CVS 1596) check-in: 1c6a0706 user: drh tags: trunk
01:40
Do not use the page containing locks for anything to avoid problems with the manditory file locking on windows. (CVS 1595) check-in: 5a814202 user: drh tags: trunk
00:29
Add the sqlite3OsFileModTime() interface. But it is still unused. The change counter in page 1 is always incremented. (CVS 1594) check-in: 186c6f93 user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/btree.c.

5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
...
203
204
205
206
207
208
209

210
211
212
213
214
215
216
....
4142
4143
4144
4145
4146
4147
4148




4149
4150
4151
4152
4153
4154
4155
** 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.
**
*************************************************************************
** $Id: btree.c,v 1.166 2004/06/14 06:03:57 danielk1977 Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
................................................................................
**      4     Page number of next trunk page
**      4     Number of leaf pointers on this page
**      *     zero or more pages numbers of leaves
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"

#include <assert.h>


/* Maximum page size.  The upper bound on this value is 65536 (a limit
** imposed by the 2-byte size of cell array pointers.)  The
** maximum page size determines the amount of stack space allocated
** by many of the routines in this module.  On embedded architectures
................................................................................
  sCheck.nPage = sqlite3pager_pagecount(sCheck.pPager);
  if( sCheck.nPage==0 ){
    unlockBtreeIfUnused(pBt);
    return 0;
  }
  sCheck.anRef = sqliteMallocRaw( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
  for(i=0; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }




  sCheck.zErrMsg = 0;

  /* Check the integrity of the freelist
  */
  checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
            get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");








|







 







>







 







>
>
>
>







5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
...
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
....
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
** 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.
**
*************************************************************************
** $Id: btree.c,v 1.167 2004/06/15 01:40:29 drh Exp $
**
** This file implements a external (disk-based) database using BTrees.
** For a detailed discussion of BTrees, refer to
**
**     Donald E. Knuth, THE ART OF COMPUTER PROGRAMMING, Volume 3:
**     "Sorting And Searching", pages 473-480. Addison-Wesley
**     Publishing Company, Reading, Massachusetts.
................................................................................
**      4     Page number of next trunk page
**      4     Number of leaf pointers on this page
**      *     zero or more pages numbers of leaves
*/
#include "sqliteInt.h"
#include "pager.h"
#include "btree.h"
#include "os.h"
#include <assert.h>


/* Maximum page size.  The upper bound on this value is 65536 (a limit
** imposed by the 2-byte size of cell array pointers.)  The
** maximum page size determines the amount of stack space allocated
** by many of the routines in this module.  On embedded architectures
................................................................................
  sCheck.nPage = sqlite3pager_pagecount(sCheck.pPager);
  if( sCheck.nPage==0 ){
    unlockBtreeIfUnused(pBt);
    return 0;
  }
  sCheck.anRef = sqliteMallocRaw( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
  for(i=0; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
  i = PENDING_BYTE/pBt->pageSize + 1;
  if( i<=sCheck.nPage ){
    sCheck.anRef[i] = 1;
  }
  sCheck.zErrMsg = 0;

  /* Check the integrity of the freelist
  */
  checkList(&sCheck, 1, get4byte(&pBt->pPage1->aData[32]),
            get4byte(&pBt->pPage1->aData[36]), "Main freelist: ");

Changes to src/os.h.

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
...
125
126
127
128
129
130
131
132



133
134
135
136












137




138
139
140
141
142
143
144
145
146
147
148
#define NO_LOCK         0
#define SHARED_LOCK     1
#define RESERVED_LOCK   2
#define PENDING_LOCK    3
#define EXCLUSIVE_LOCK  4

/*
** Windows file locking notes:
**
** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
** those functions are not available.  So we use only LockFile() and
** UnlockFile().
**
** LockFile() prevents not just writing but also reading by other processes.
** (This is a design error on the part of Windows, but there is nothing
** we can do about that.)  So the region used for locking is at the
** end of the file where it is unlikely to ever interfere with an
** actual read attempt.
**
** A SHARED_LOCK is obtained by locking a single randomly-chosen 
** byte out of a specific range of bytes. The lock byte is obtained at 
** random so two separate readers can probably access the file at the 
** same time, unless they are unlucky and choose the same lock byte.
** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.
** There can only be one writer.  A RESERVED_LOCK is obtained by locking
** a single byte of the file that is designated as the reserved lock byte.
................................................................................
** SHARED_SIZE is the number of bytes available in the pool from which
** a random byte is selected for a shared lock.  The pool of bytes for
** shared locks begins at SHARED_FIRST. 
**
** These #defines are available in os.h so that Unix can use the same
** byte ranges for locking.  This leaves open the possiblity of having
** clients on win95, winNT, and unix all talking to the same shared file
** and all locking correctly.



**
** Locking in windows is manditory.  For this reason, we cannot store
** actual data in the bytes used for locking.  The pager never allocates
** the pages involved in locking therefore.












*/




#define SHARED_SIZE       10238
#define SHARED_FIRST      (0x3fffffff - (SHARED_SIZE - 1))
#define RESERVED_BYTE     (SHARED_FIRST - 1)
#define PENDING_BYTE      (RESERVED_BYTE - 1)


int sqlite3OsDelete(const char*);
int sqlite3OsFileExists(const char*);
int sqliteOsFileRename(const char*, const char*);
int sqlite3OsOpenReadWrite(const char*, OsFile*, int*);
int sqlite3OsOpenExclusive(const char*, OsFile*, int);







|






<
<
<
<
<







 







|
>
>
>



|
>
>
>
>
>
>
>
>
>
>
>
>

>
>
>
>
|
<
<
<







87
88
89
90
91
92
93
94
95
96
97
98
99
100





101
102
103
104
105
106
107
...
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
#define NO_LOCK         0
#define SHARED_LOCK     1
#define RESERVED_LOCK   2
#define PENDING_LOCK    3
#define EXCLUSIVE_LOCK  4

/*
** File Locking Notes:  (Mostly about windows but also some info for Unix)
**
** We cannot use LockFileEx() or UnlockFileEx() on Win95/98/ME because
** those functions are not available.  So we use only LockFile() and
** UnlockFile().
**
** LockFile() prevents not just writing but also reading by other processes.





** A SHARED_LOCK is obtained by locking a single randomly-chosen 
** byte out of a specific range of bytes. The lock byte is obtained at 
** random so two separate readers can probably access the file at the 
** same time, unless they are unlucky and choose the same lock byte.
** An EXCLUSIVE_LOCK is obtained by locking all bytes in the range.
** There can only be one writer.  A RESERVED_LOCK is obtained by locking
** a single byte of the file that is designated as the reserved lock byte.
................................................................................
** SHARED_SIZE is the number of bytes available in the pool from which
** a random byte is selected for a shared lock.  The pool of bytes for
** shared locks begins at SHARED_FIRST. 
**
** These #defines are available in os.h so that Unix can use the same
** byte ranges for locking.  This leaves open the possiblity of having
** clients on win95, winNT, and unix all talking to the same shared file
** and all locking correctly.  To do so would require that samba (or whatever
** tool is being used for file sharing) implements locks correctly between
** windows and unix.  I'm guessing that isn't likely to happen, but by
** using the same locking range we are at least open to the possibility.
**
** Locking in windows is manditory.  For this reason, we cannot store
** actual data in the bytes used for locking.  The pager never allocates
** the pages involved in locking therefore.  SHARED_SIZE is selected so
** that all locks will fit on a single page even at the minimum page size.
** PENDING_BYTE defines the beginning of the locks.  By default PENDING_BYTE
** is set high so that we don't have to allocate an unused page except
** for very large databases.  But one should test the page skipping logic 
** by setting PENDING_BYTE low and running the entire regression suite.
**
** Changing the value of PENDING_BYTE results in a subtly incompatible
** file format.  Depending on how it is changed, you might not notice
** the incompatibility right away, even running a full regression test.
** The default location of PENDING_BYTE is the first byte past the
** 1GB boundary.
**
*/
#define PENDING_BYTE      0x40000000  /* First byte past the 1GB boundary */
/* #define PENDING_BYTE     0x5400   // Page 20 - for testing */
#define RESERVED_BYTE     (PENDING_BYTE+1)
#define SHARED_FIRST      (PENDING_BYTE+2)
#define SHARED_SIZE       510





int sqlite3OsDelete(const char*);
int sqlite3OsFileExists(const char*);
int sqliteOsFileRename(const char*, const char*);
int sqlite3OsOpenReadWrite(const char*, OsFile*, int*);
int sqlite3OsOpenExclusive(const char*, OsFile*, int);

Changes to src/pager.c.

14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
....
1201
1202
1203
1204
1205
1206
1207



1208
1209
1210
1211
1212
1213
1214
....
2205
2206
2207
2208
2209
2210
2211



2212
2213
2214
2215
2216
2217
2218
** 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.
**
** @(#) $Id: pager.c,v 1.126 2004/06/14 06:03:57 danielk1977 Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

................................................................................
    return pPager->dbSize;
  }
  if( sqlite3OsFileSize(&pPager->fd, &n)!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_DISK;
    return 0;
  }
  n /= SQLITE_PAGE_SIZE;



  if( pPager->state!=PAGER_UNLOCK ){
    pPager->dbSize = n;
  }
  return n;
}

/*
................................................................................
    page_add_to_stmt_list(pPg);
  }

  /* Update the database size and return.
  */
  if( pPager->dbSize<(int)pPg->pgno ){
    pPager->dbSize = pPg->pgno;



  }
  return rc;
}

/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3pager_write().  In other words, return TRUE if it is ok







|







 







>
>
>







 







>
>
>







14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
....
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
....
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
** 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.
**
** @(#) $Id: pager.c,v 1.127 2004/06/15 01:40:29 drh Exp $
*/
#include "os.h"         /* Must be first to enable large file support */
#include "sqliteInt.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

................................................................................
    return pPager->dbSize;
  }
  if( sqlite3OsFileSize(&pPager->fd, &n)!=SQLITE_OK ){
    pPager->errMask |= PAGER_ERR_DISK;
    return 0;
  }
  n /= SQLITE_PAGE_SIZE;
  if( !pPager->memDb && n==PENDING_BYTE/SQLITE_PAGE_SIZE ){
    n++;
  }
  if( pPager->state!=PAGER_UNLOCK ){
    pPager->dbSize = n;
  }
  return n;
}

/*
................................................................................
    page_add_to_stmt_list(pPg);
  }

  /* Update the database size and return.
  */
  if( pPager->dbSize<(int)pPg->pgno ){
    pPager->dbSize = pPg->pgno;
    if( !pPager->memDb && pPager->dbSize==PENDING_BYTE/pPager->pageSize ){
      pPager->dbSize++;
    }
  }
  return rc;
}

/*
** Return TRUE if the page given in the argument was previously passed
** to sqlite3pager_write().  In other words, return TRUE if it is ok