SQLite

** how well the database resists damage due to OS crashes and power
** failures.  Level 1 is the same as asynchronous (no syncs() occur and
** there is a high probability of damage)  Level 2 is the default.  There
** is a very low but non-zero probability of damage.  Level 3 reduces the
** probability of damage to near zero but with a write performance reduction.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
int sqlite3BtreeSetPagerFlags(
  Btree *p,              /* The btree to set the safety level on */


  unsigned pgFlags       /* Various PAGER_* flags */
){
  BtShared *pBt = p->pBt;
  assert( sqlite3_mutex_held(p->db->mutex) );

  sqlite3BtreeEnter(p);
  sqlite3PagerSetFlags(pBt->pPager, pgFlags);
  sqlite3BtreeLeave(p);
  return SQLITE_OK;
}
#endif

/*
** Return TRUE if the given btree is set to safety level 1.  In other

#define BTREE_MEMORY        2  /* This is an in-memory DB */
#define BTREE_SINGLE        4  /* The file contains at most 1 b-tree */
#define BTREE_UNORDERED     8  /* Use of a hash implementation is OK */

int sqlite3BtreeClose(Btree*);
int sqlite3BtreeSetCacheSize(Btree*,int);
int sqlite3BtreeSetMmapLimit(Btree*,sqlite3_int64);
int sqlite3BtreeSetPagerFlags(Btree*,unsigned);
int sqlite3BtreeSyncDisabled(Btree*);
int sqlite3BtreeSetPageSize(Btree *p, int nPagesize, int nReserve, int eFix);
int sqlite3BtreeGetPageSize(Btree*);
int sqlite3BtreeMaxPageCount(Btree*,int);
u32 sqlite3BtreeLastPage(Btree*);
int sqlite3BtreeSecureDelete(Btree*,int);
int sqlite3BtreeGetReserve(Btree*);

  assert( sizeof(db->aLimit)==sizeof(aHardLimit) );
  memcpy(db->aLimit, aHardLimit, sizeof(db->aLimit));
  db->autoCommit = 1;
  db->nextAutovac = -1;
  db->szMmap = sqlite3GlobalConfig.szMmap;
  db->nextPagesize = 0;
  db->flags |= SQLITE_ShortColNames | SQLITE_EnableTrigger | SQLITE_CacheSpill
#if !defined(SQLITE_DEFAULT_AUTOMATIC_INDEX) || SQLITE_DEFAULT_AUTOMATIC_INDEX
                 | SQLITE_AutoIndex
#endif
#if SQLITE_DEFAULT_FILE_FORMAT<4
                 | SQLITE_LegacyFileFmt
#endif
#ifdef SQLITE_ENABLE_LOAD_EXTENSION

  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
};

/*
** Bits of the Pager.doNotSpill flag.  See further description below.
*/
#define SPILLFLAG_OFF         0x01      /* Never spill cache.  Set via pragma */
#define SPILLFLAG_ROLLBACK    0x02      /* Current rolling back, so do not spill */
#define SPILLFLAG_NOSYNC      0x04      /* Spill is ok, but do not sync */

/*
** A open page cache is an instance of struct Pager. A description of
** some of the more important member variables follows:
**
** eState
**
**   The current 'state' of the pager object. See the comment and state

**   subsequently interrupted transaction that reuses the journal file.
**
**   The flag is cleared as soon as the journal file is finalized (either
**   by PagerCommitPhaseTwo or PagerRollback). If an IO error prevents the
**   journal file from being successfully finalized, the setMaster flag
**   is cleared anyway (and the pager will move to ERROR state).
**
** doNotSpill
**
**   This variables control the behavior of cache-spills  (calls made by
**   the pcache module to the pagerStress() routine to write cached data
**   to the file-system in order to free up memory).
**
**   When bits SPILLFLAG_OFF or SPILLFLAG_ROLLBACK of doNotSpill are set,
**   writing to the database from pagerStress() is disabled altogether.
**   The SPILLFLAG_ROLLBACK case is done in a very obscure case that
**   comes up during savepoint rollback that requires the pcache module
**   to allocate a new page to prevent the journal file from being written
**   while it is being traversed by code in pager_playback().  The SPILLFLAG_OFF
**   case is a user preference.
** 
**   If the SPILLFLAG_NOSYNC bit is set, writing to the database from pagerStress()
**   is permitted, but syncing the journal file is not. This flag is set
**   by sqlite3PagerWrite() when the file-system sector-size is larger than
**   the database page-size in order to prevent a journal sync from happening 
**   in between the journalling of two pages on the same sector. 
**
** subjInMemory
**

  ** "configuration" of the pager.
  */
  u8 eState;                  /* Pager state (OPEN, READER, WRITER_LOCKED..) */
  u8 eLock;                   /* Current lock held on database file */
  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 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 */
  Pgno dbHintSize;            /* Value passed to FCNTL_SIZE_HINT call */
  int errCode;                /* One of several kinds of errors */
  int nRec;                   /* Pages journalled since last j-header written */

    **
    ** 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 & SPILLFLAG_ROLLBACK)==0 );
    pPager->doNotSpill |= SPILLFLAG_ROLLBACK;
    rc = sqlite3PagerAcquire(pPager, pgno, &pPg, 1);
    assert( (pPager->doNotSpill & SPILLFLAG_ROLLBACK)!=0 );
    pPager->doNotSpill &= ~SPILLFLAG_ROLLBACK;
    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

** Free as much memory as possible from the pager.
*/
void sqlite3PagerShrink(Pager *pPager){
  sqlite3PcacheShrink(pPager->pPCache);
}

/*
** Adjust settings of the pager to those specified in the pgFlags parameter.
**
** The "level" in pgFlags & PAGER_SYNCHRONOUS_MASK sets the robustness
** of the database to damage due to OS crashes or power failures by
** changing the number of syncs()s when writing the journals.
** 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,

** synchronous=FULL versus synchronous=NORMAL setting determines when
** the xSync primitive is called and is relevant to all platforms.
**
** Numeric values associated with these states are OFF==1, NORMAL=2,
** and FULL=3.
*/
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
void sqlite3PagerSetFlags(
  Pager *pPager,        /* The pager to set safety level for */

  unsigned pgFlags      /* Various flags */

){
  unsigned level = pgFlags & PAGER_SYNCHRONOUS_MASK;
  assert( level>=1 && level<=3 );
  pPager->noSync =  (level==1 || pPager->tempFile) ?1:0;
  pPager->fullSync = (level==3 && !pPager->tempFile) ?1:0;
  if( pPager->noSync ){
    pPager->syncFlags = 0;
    pPager->ckptSyncFlags = 0;
  }else if( pgFlags & PAGER_FULLFSYNC ){
    pPager->syncFlags = SQLITE_SYNC_FULL;
    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
  }else if( pgFlags & PAGER_CKPT_FULLFSYNC ){
    pPager->syncFlags = SQLITE_SYNC_NORMAL;
    pPager->ckptSyncFlags = SQLITE_SYNC_FULL;
  }else{
    pPager->syncFlags = SQLITE_SYNC_NORMAL;
    pPager->ckptSyncFlags = SQLITE_SYNC_NORMAL;
  }
  pPager->walSyncFlags = pPager->syncFlags;
  if( pPager->fullSync ){
    pPager->walSyncFlags |= WAL_SYNC_TRANSACTIONS;
  }
  if( pgFlags & PAGER_CACHESPILL ){
    pPager->doNotSpill &= ~SPILLFLAG_OFF;
  }else{
    pPager->doNotSpill |= SPILLFLAG_OFF;
  }
}
#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.  

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 doNotSpill NOSYNC bit 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 ROLLBACK and OFF bits inhibits all cache spilling
  ** regardless of whether or not a sync is required.  This is set during
  ** a rollback or by user request, respectively.
  **
  ** Spilling is also prohibited when in an error state since that could
  ** lead to database corruption.   In the current implementaton it 
  ** is impossible for sqlite3PcacheFetch() to be called with createFlag==1
  ** while in the error state, hence it is impossible for this routine to
  ** be called in the error state.  Nevertheless, we include a NEVER()
  ** test for the error state as a safeguard against future changes.
  */
  if( NEVER(pPager->errCode) ) return SQLITE_OK;
  testcase( pPager->doNotSpill & SPILLFLAG_ROLLBACK );
  testcase( pPager->doNotSpill & SPILLFLAG_OFF );
  testcase( pPager->doNotSpill & SPILLFLAG_NOSYNC );
  if( pPager->doNotSpill
   && ((pPager->doNotSpill & (SPILLFLAG_ROLLBACK|SPILLFLAG_OFF))!=0
      || (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) ){ 

  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 doNotSpill NOSYNC bit 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->doNotSpill & SPILLFLAG_NOSYNC)==0 );
    pPager->doNotSpill |= SPILLFLAG_NOSYNC;

    /* 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;

        if( pPage ){
          pPage->flags |= PGHDR_NEED_SYNC;
          sqlite3PagerUnref(pPage);
        }
      }
    }

    assert( (pPager->doNotSpill & SPILLFLAG_NOSYNC)!=0 );
    pPager->doNotSpill &= ~SPILLFLAG_NOSYNC;
  }else{
    rc = pager_write(pDbPage);
  }
  return rc;
}

/*

/*
** Flags that make up the mask passed to sqlite3PagerAcquire().
*/
#define PAGER_ACQUIRE_NOCONTENT     0x01  /* Do not load data from disk */
#define PAGER_ACQUIRE_READONLY      0x02  /* Read-only page is acceptable */

/*
** Flags for sqlite3PagerSetFlags()
*/
#define PAGER_SYNCHRONOUS_OFF       0x01  /* PRAGMA synchronous=OFF */
#define PAGER_SYNCHRONOUS_NORMAL    0x02  /* PRAGMA synchronous=NORMAL */
#define PAGER_SYNCHRONOUS_FULL      0x03  /* PRAGMA synchronous=FULL */
#define PAGER_SYNCHRONOUS_MASK      0x03  /* Mask for three values above */
#define PAGER_FULLFSYNC             0x04  /* PRAGMA fullfsync=ON */
#define PAGER_CKPT_FULLFSYNC        0x08  /* PRAGMA checkpoint_fullfsync=ON */
#define PAGER_CACHESPILL            0x10  /* PRAGMA cache_spill=ON */
#define PAGER_FLAGS_MASK            0x1c  /* All above except SYNCHRONOUS */

/*
** The remainder of this file contains the declarations of the functions
** that make up the Pager sub-system API. See source code comments for 
** a detailed description of each routine.
*/

/* Open and close a Pager connection. */ 

/* Functions used to configure a Pager object. */
void sqlite3PagerSetBusyhandler(Pager*, int(*)(void *), void *);
int sqlite3PagerSetPagesize(Pager*, u32*, int);
int sqlite3PagerMaxPageCount(Pager*, int);
void sqlite3PagerSetCachesize(Pager*, int);
void sqlite3PagerSetMmapLimit(Pager *, sqlite3_int64);
void sqlite3PagerShrink(Pager*);
void sqlite3PagerSetFlags(Pager*,unsigned);
int sqlite3PagerLockingMode(Pager *, int);
int sqlite3PagerSetJournalMode(Pager *, int);
int sqlite3PagerGetJournalMode(Pager*);
int sqlite3PagerOkToChangeJournalMode(Pager*);
i64 sqlite3PagerJournalSizeLimit(Pager *, i64);
sqlite3_backup **sqlite3PagerBackupPtr(Pager*);

    { "full_column_names",        SQLITE_FullColNames  },
    { "short_column_names",       SQLITE_ShortColNames },
    { "count_changes",            SQLITE_CountRows     },
    { "empty_result_callbacks",   SQLITE_NullCallback  },
    { "legacy_file_format",       SQLITE_LegacyFileFmt },
    { "fullfsync",                SQLITE_FullFSync     },
    { "checkpoint_fullfsync",     SQLITE_CkptFullFSync },
    { "cache_spill",              SQLITE_CacheSpill    },
    { "reverse_unordered_selects", SQLITE_ReverseOrder  },
    { "query_only",               SQLITE_QueryOnly     },
#ifndef SQLITE_OMIT_AUTOMATIC_INDEX
    { "automatic_index",          SQLITE_AutoIndex     },
#endif
#ifdef SQLITE_DEBUG
    { "sql_trace",                SQLITE_SqlTrace      },

  /*
  ** Reset the safety level, in case the fullfsync flag or synchronous
  ** setting changed.
  */
#ifndef SQLITE_OMIT_PAGER_PRAGMAS
  if( db->autoCommit ){
    assert( (pDb->safety_level & PAGER_SYNCHRONOUS_MASK)==pDb->safety_level );
    assert( SQLITE_FullFSync==PAGER_FULLFSYNC );
    assert( SQLITE_CkptFullFSync==PAGER_CKPT_FULLFSYNC );
    assert( SQLITE_CacheSpill==PAGER_CACHESPILL );
    assert( (PAGER_FULLFSYNC | PAGER_CKPT_FULLFSYNC | PAGER_CACHESPILL)
             ==  PAGER_FLAGS_MASK );
    sqlite3BtreeSetPagerFlags(pDb->pBt,
                     pDb->safety_level | (db->flags & PAGER_FLAGS_MASK) );
  }
#endif
pragma_out:
  sqlite3DbFree(db, zLeft);
  sqlite3DbFree(db, zRight);
}

#endif /* SQLITE_OMIT_PRAGMA */

#define ENC(db) ((db)->aDb[0].pSchema->enc)

/*
** Possible values for the sqlite3.flags.
*/
#define SQLITE_VdbeTrace      0x00000001  /* True to trace VDBE execution */
#define SQLITE_InternChanges  0x00000002  /* Uncommitted Hash table changes */
#define SQLITE_FullFSync      0x00000004  /* Use full fsync on the backend */
#define SQLITE_CkptFullFSync  0x00000008  /* Use full fsync for checkpoint */
#define SQLITE_CacheSpill     0x00000010  /* OK to spill pager cache */
#define SQLITE_FullColNames   0x00000020  /* Show full column names on SELECT */
#define SQLITE_ShortColNames  0x00000040  /* Show short columns names */
#define SQLITE_CountRows      0x00000080  /* Count rows changed by INSERT, */
                                          /*   DELETE, or UPDATE and return */
                                          /*   the count using a callback. */
#define SQLITE_NullCallback   0x00000100  /* Invoke the callback once if the */
                                          /*   result set is empty */
#define SQLITE_SqlTrace       0x00000200  /* Debug print SQL as it executes */
#define SQLITE_VdbeListing    0x00000400  /* Debug listings of VDBE programs */
#define SQLITE_WriteSchema    0x00000800  /* OK to update SQLITE_MASTER */
#define SQLITE_VdbeAddopTrace 0x00001000  /* Trace sqlite3VdbeAddOp() calls */
#define SQLITE_IgnoreChecks   0x00002000  /* Do not enforce check constraints */
#define SQLITE_ReadUncommitted 0x0004000  /* For shared-cache mode */
#define SQLITE_LegacyFileFmt  0x00008000  /* Create new databases in format 1 */


#define SQLITE_RecoveryMode   0x00010000  /* Ignore schema errors */
#define SQLITE_ReverseOrder   0x00020000  /* Reverse unordered SELECTs */
#define SQLITE_RecTriggers    0x00040000  /* Enable recursive triggers */
#define SQLITE_ForeignKeys    0x00080000  /* Enforce foreign key constraints  */
#define SQLITE_AutoIndex      0x00100000  /* Enable automatic indexes */
#define SQLITE_PreferBuiltin  0x00200000  /* Preference to built-in funcs */
#define SQLITE_LoadExtension  0x00400000  /* Enable load_extension */
#define SQLITE_EnableTrigger  0x00800000  /* True to enable triggers */
#define SQLITE_DeferFKs       0x01000000  /* Defer all FK constraints */
#define SQLITE_QueryOnly      0x02000000  /* Disable database changes */


/*
** Bits of the sqlite3.dbOptFlags field that are used by the
** sqlite3_test_control(SQLITE_TESTCTRL_OPTIMIZATIONS,...) interface to
** selectively disable various optimizations.
*/