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Overview
Comment:Add the immutable=TRUE query parameter and SQLITE_IOCAP_IMMUTABLE, either of which prevents locking of the database and omits tests for existance of journal files.
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SHA1: 71f152c85d79ebd9ca48bc9c4c71fc4debaf2437
User & Date: drh 2014-05-01 01:13:08.624
Context
2014-05-01
01:20
Avoid unnecessary xUnlock operations on temp file. (check-in: 1829c38c32 user: drh tags: win32-none)
01:13
Add the immutable=TRUE query parameter and SQLITE_IOCAP_IMMUTABLE, either of which prevents locking of the database and omits tests for existance of journal files. (check-in: 71f152c85d user: drh tags: win32-none)
2014-04-30
20:32
Merge in all recent changes and enhancements from trunk. (check-in: 84243f8444 user: drh tags: win32-none)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/pager.c.
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    ** 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 = (u32)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->eState = PAGER_READER;
    pPager->eLock = EXCLUSIVE_LOCK;
    readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
  }

  /* The following call to PagerSetPagesize() serves to set the value of 








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    ** 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 ){
      if( !readOnly ){
        int iDc = sqlite3OsDeviceCharacteristics(pPager->fd);
        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 = (u32)pPager->sectorSize;
          }
        }
#ifdef SQLITE_ENABLE_ATOMIC_WRITE
        {

          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
        if( (iDc & SQLITE_IOCAP_IMMUTABLE)!=0
         || sqlite3_uri_boolean(zFilename, "immutable", 0) ){
            vfsFlags |= SQLITE_OPEN_READONLY;
            goto act_like_temp_file;
        }
      }
    }
  }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.
    */ 
act_like_temp_file:
    tempFile = 1;
    pPager->eState = PAGER_READER;
    pPager->eLock = EXCLUSIVE_LOCK;
    readOnly = (vfsFlags&SQLITE_OPEN_READONLY);
  }

  /* The following call to PagerSetPagesize() serves to set the value of
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  /* pPager->stmtInUse = 0; */
  /* pPager->nRef = 0; */
  /* pPager->stmtSize = 0; */
  /* pPager->stmtJSize = 0; */
  /* pPager->nPage = 0; */
  pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
  /* pPager->state = PAGER_UNLOCK; */
#if 0
  assert( pPager->state == (tempFile ? PAGER_EXCLUSIVE : PAGER_UNLOCK) );
#endif
  /* 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;








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  /* pPager->stmtInUse = 0; */
  /* pPager->nRef = 0; */
  /* pPager->stmtSize = 0; */
  /* pPager->stmtJSize = 0; */
  /* pPager->nPage = 0; */
  pPager->mxPgno = SQLITE_MAX_PAGE_COUNT;
  /* pPager->state = 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;
︙︙
Changes to src/sqlite.h.in.
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** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
** information is written to disk in the same order as calls
** to xWrite().  The SQLITE_IOCAP_POWERSAFE_OVERWRITE property means that
** after reboot following a crash or power loss, the only bytes in a
** file that were written at the application level might have changed
** and that adjacent bytes, even bytes within the same sector are
** guaranteed to be unchanged.  The SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
** flag indicate that a file cannot be deleted when open.



*/
#define SQLITE_IOCAP_ATOMIC                 0x00000001
#define SQLITE_IOCAP_ATOMIC512              0x00000002
#define SQLITE_IOCAP_ATOMIC1K               0x00000004
#define SQLITE_IOCAP_ATOMIC2K               0x00000008
#define SQLITE_IOCAP_ATOMIC4K               0x00000010
#define SQLITE_IOCAP_ATOMIC8K               0x00000020
#define SQLITE_IOCAP_ATOMIC16K              0x00000040
#define SQLITE_IOCAP_ATOMIC32K              0x00000080
#define SQLITE_IOCAP_ATOMIC64K              0x00000100
#define SQLITE_IOCAP_SAFE_APPEND            0x00000200
#define SQLITE_IOCAP_SEQUENTIAL             0x00000400
#define SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN  0x00000800
#define SQLITE_IOCAP_POWERSAFE_OVERWRITE    0x00001000


/*
** CAPI3REF: File Locking Levels
**
** SQLite uses one of these integer values as the second
** argument to calls it makes to the xLock() and xUnlock() methods
** of an [sqlite3_io_methods] object.








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** way around.  The SQLITE_IOCAP_SEQUENTIAL property means that
** information is written to disk in the same order as calls
** to xWrite().  The SQLITE_IOCAP_POWERSAFE_OVERWRITE property means that
** after reboot following a crash or power loss, the only bytes in a
** file that were written at the application level might have changed
** and that adjacent bytes, even bytes within the same sector are
** guaranteed to be unchanged.  The SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN
** flag indicate that a file cannot be deleted when open.  The
** SQLITE_IOCAP_IMMUTABLE flag indicates that the file is on
** read-only media and cannot be changed even by processes with
** elevated privileges.
*/
#define SQLITE_IOCAP_ATOMIC                 0x00000001
#define SQLITE_IOCAP_ATOMIC512              0x00000002
#define SQLITE_IOCAP_ATOMIC1K               0x00000004
#define SQLITE_IOCAP_ATOMIC2K               0x00000008
#define SQLITE_IOCAP_ATOMIC4K               0x00000010
#define SQLITE_IOCAP_ATOMIC8K               0x00000020
#define SQLITE_IOCAP_ATOMIC16K              0x00000040
#define SQLITE_IOCAP_ATOMIC32K              0x00000080
#define SQLITE_IOCAP_ATOMIC64K              0x00000100
#define SQLITE_IOCAP_SAFE_APPEND            0x00000200
#define SQLITE_IOCAP_SEQUENTIAL             0x00000400
#define SQLITE_IOCAP_UNDELETABLE_WHEN_OPEN  0x00000800
#define SQLITE_IOCAP_POWERSAFE_OVERWRITE    0x00001000
#define SQLITE_IOCAP_IMMUTABLE              0x00002000

/*
** CAPI3REF: File Locking Levels
**
** SQLite uses one of these integer values as the second
** argument to calls it makes to the xLock() and xUnlock() methods
** of an [sqlite3_io_methods] object.
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