1 files changed, 38 insertions, 14 deletions

diff --git a/lib/libsqlite3/src/pager.c b/lib/libsqlite3/src/pager.c
index d840a39a159..2230174e5cb 100644
--- a/lib/libsqlite3/src/pager.c
+++ b/lib/libsqlite3/src/pager.c
@@ -646,6 +646,8 @@ struct Pager {
   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 */
+  u8 bUseFetch;               /* True to use xFetch() */
+  u8 hasBeenUsed;             /* True if any content previously read from this pager*/
   Pgno dbSize;                /* Number of pages in the database */
   Pgno dbOrigSize;            /* dbSize before the current transaction */
   Pgno dbFileSize;            /* Number of pages in the database file */
@@ -663,9 +665,9 @@ struct Pager {
   sqlite3_backup *pBackup;    /* Pointer to list of ongoing backup processes */
   PagerSavepoint *aSavepoint; /* Array of active savepoints */
   int nSavepoint;             /* Number of elements in aSavepoint[] */
+  u32 iDataVersion;           /* Changes whenever database content changes */
   char dbFileVers[16];        /* Changes whenever database file changes */
 
-  u8 bUseFetch;               /* True to use xFetch() */
   int nMmapOut;               /* Number of mmap pages currently outstanding */
   sqlite3_int64 szMmap;       /* Desired maximum mmap size */
   PgHdr *pMmapFreelist;       /* List of free mmap page headers (pDirty) */
@@ -1681,11 +1683,20 @@ static int writeMasterJournal(Pager *pPager, const char *zMaster){
 ** Discard the entire contents of the in-memory page-cache.
 */
 static void pager_reset(Pager *pPager){
+  pPager->iDataVersion++;
   sqlite3BackupRestart(pPager->pBackup);
   sqlite3PcacheClear(pPager->pPCache);
 }
 
 /*
+** Return the pPager->iDataVersion value
+*/
+u32 sqlite3PagerDataVersion(Pager *pPager){
+  assert( pPager->eState>PAGER_OPEN );
+  return pPager->iDataVersion;
+}
+
+/*
 ** 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.
@@ -2899,7 +2910,7 @@ static int readDbPage(PgHdr *pPg, u32 iFrame){
       **
       ** 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
+      ** white noise equaling 16 bytes of 0xff is vanishingly small so
       ** we should still be ok.
       */
       memset(pPager->dbFileVers, 0xff, sizeof(pPager->dbFileVers));
@@ -3887,7 +3898,7 @@ static int pagerAcquireMapPage(
   PgHdr **ppPage                  /* OUT: Acquired page object */
 ){
   PgHdr *p;                       /* Memory mapped page to return */
-
+  
   if( pPager->pMmapFreelist ){
     *ppPage = p = pPager->pMmapFreelist;
     pPager->pMmapFreelist = p->pDirty;
@@ -5118,16 +5129,12 @@ int sqlite3PagerSharedLock(Pager *pPager){
       );
     }
 
-    if( !pPager->tempFile && (
-        pPager->pBackup 
-     || sqlite3PcachePagecount(pPager->pPCache)>0 
-     || USEFETCH(pPager)
-    )){
-      /* 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.
+    if( !pPager->tempFile && pPager->hasBeenUsed ){
+      /* The shared-lock has just been acquired then check to
+      ** see if the database has been modified.  If the database has changed,
+      ** flush the cache.  The pPager->hasBeenUsed flag prevents this from
+      ** occurring on the very first access to a file, in order to save a
+      ** single unnecessary sqlite3OsRead() call at the start-up.
       **
       ** Database changes is detected by looking at 15 bytes beginning
       ** at offset 24 into the file.  The first 4 of these 16 bytes are
@@ -5292,6 +5299,7 @@ int sqlite3PagerAcquire(
   if( pgno==0 ){
     return SQLITE_CORRUPT_BKPT;
   }
+  pPager->hasBeenUsed = 1;
 
   /* If the pager is in the error state, return an error immediately. 
   ** Otherwise, request the page from the PCache layer. */
@@ -5441,6 +5449,7 @@ DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
   assert( pgno!=0 );
   assert( pPager->pPCache!=0 );
   pPage = sqlite3PcacheFetch(pPager->pPCache, pgno, 0);
+  assert( pPage==0 || pPager->hasBeenUsed );
   return sqlite3PcacheFetchFinish(pPager->pPCache, pgno, pPage);
 }
 
@@ -6307,6 +6316,7 @@ int sqlite3PagerCommitPhaseTwo(Pager *pPager){
   }
 
   PAGERTRACE(("COMMIT %d\n", PAGERID(pPager)));
+  pPager->iDataVersion++;
   rc = pager_end_transaction(pPager, pPager->setMaster, 1);
   return pager_error(pPager, rc);
 }
@@ -6848,6 +6858,18 @@ int sqlite3PagerMovepage(Pager *pPager, DbPage *pPg, Pgno pgno, int isCommit){
 #endif
 
 /*
+** The page handle passed as the first argument refers to a dirty page 
+** with a page number other than iNew. This function changes the page's 
+** page number to iNew and sets the value of the PgHdr.flags field to 
+** the value passed as the third parameter.
+*/
+void sqlite3PagerRekey(DbPage *pPg, Pgno iNew, u16 flags){
+  assert( pPg->pgno!=iNew );
+  pPg->flags = flags;
+  sqlite3PcacheMove(pPg, iNew);
+}
+
+/*
 ** Return a pointer to the data for the specified page.
 */
 void *sqlite3PagerGetData(DbPage *pPg){
@@ -7063,7 +7085,8 @@ int sqlite3PagerCheckpoint(Pager *pPager, int eMode, int *pnLog, int *pnCkpt){
   int rc = SQLITE_OK;
   if( pPager->pWal ){
     rc = sqlite3WalCheckpoint(pPager->pWal, eMode,
-        pPager->xBusyHandler, pPager->pBusyHandlerArg,
+        (eMode==SQLITE_CHECKPOINT_PASSIVE ? 0 : pPager->xBusyHandler),
+        pPager->pBusyHandlerArg,
         pPager->ckptSyncFlags, pPager->pageSize, (u8 *)pPager->pTmpSpace,
         pnLog, pnCkpt
     );
@@ -7245,4 +7268,5 @@ int sqlite3PagerWalFramesize(Pager *pPager){
 }
 #endif
 
+
 #endif /* SQLITE_OMIT_DISKIO */