Avoid moving pages more than once in an incremental vacuum operation.

FossilOrigin-Name: c3939d249119b47bd57baa11a5ed7cc6014fc795

manifest

@@ -1,5 +1,5 @@
-C On\sMinix,\sdisable\sthe\s".timer"\scommand\sin\sthe\sshell\sin\sorder\sto\savoid\ncalling\sgetrusage().
+C Avoid\smoving\spages\smore\sthan\sonce\sin\san\sincremental\svacuum\soperation.
-D 2013-02-20T00:54:21.855
+D 2013-02-22T20:16:34.273
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in a48faa9e7dd7d556d84f5456eabe5825dd8a6282
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -121,7 +121,7 @@ F src/auth.c 523da7fb4979469955d822ff9298352d6b31de34
 F src/backup.c 32e35a3a4ea55b45c0e5f74eeb793aec71491517
 F src/bitvec.c 26675fe8e431dc555e6f2d0e11e651d172234aa1
 F src/btmutex.c 976f45a12e37293e32cae0281b15a21d48a8aaa7
-F src/btree.c 7a80e4a67f32a2494c383a28a495bf3bd71cc230
+F src/btree.c 960274cb93c1d85e82bd106094e0890d89434ab8
 F src/btree.h 3ad7964d6c5b1c7bff569aab6adfa075f8bf06cd
 F src/btreeInt.h 4e5c2bd0f9b36b2a815a6d84f771a61a65830621
 F src/build.c 73ca65f32938e4e0d94e831b61b5749b211b79be
@@ -1034,7 +1034,10 @@ F tool/vdbe-compress.tcl f12c884766bd14277f4fcedcae07078011717381
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh fbc018d67fd7395f440c28f33ef0f94420226381
 F tool/win/sqlite.vsix 97894c2790eda7b5bce3cc79cb2a8ec2fde9b3ac
-P 06bd91305ed6752315c5224be5f89e87cafa6687
+P 9bd9bd9cab8c804c1a51d472199459176044a633
-R 14c0fedf89f00b14b7845aeac312ffca
+R d336ad839cab7fc86035cb53790f3fce
-U drh
+T *branch * incr-vacuum-opt
-Z 673b617e6189db9a51be1e6b0160e6d4
+T *sym-incr-vacuum-opt *
+T -sym-trunk *
+U dan
+Z cd58f1fbd68ec5de5d0f48d285a49284

manifest.uuid

@@ -1 +1 @@
-9bd9bd9cab8c804c1a51d472199459176044a633
+c3939d249119b47bd57baa11a5ed7cc6014fc795

src/btree.c

@@ -2909,26 +2909,28 @@ static int relocatePage(
 
 /* Forward declaration required by incrVacuumStep(). */
 static int allocateBtreePage(BtShared *, MemPage **, Pgno *, Pgno, u8);
+#define BTALLOC_ANY   0           /* Allocate any page */
+#define BTALLOC_EXACT 1           /* Allocate exact page if possible */
+#define BTALLOC_LE    2           /* Allocate any page <= the parameter */
 
 /*
-** Perform a single step of an incremental-vacuum. If successful,
+** Perform a single step of an incremental-vacuum. If successful, return
-** return SQLITE_OK. If there is no work to do (and therefore no
+** SQLITE_OK. If there is no work to do (and therefore no point in 
-** point in calling this function again), return SQLITE_DONE.
+** calling this function again), return SQLITE_DONE. Or, if an error 
+** occurs, return some other error code.
 **
-** More specificly, this function attempts to re-organize the 
+** More specificly, this function attempts to re-organize the database so 
-** database so that the last page of the file currently in use
+** that the last page of the file currently in use is no longer in use.
-** is no longer in use.
 **
-** If the nFin parameter is non-zero, this function assumes
+** Parameter nFin is the number of pages that this database would contain
-** that the caller will keep calling incrVacuumStep() until
+** were this function called until it returns SQLITE_DONE.
-** it returns SQLITE_DONE or an error, and that nFin is the
+**
-** number of pages the database file will contain after this 
+** If the bCommit parameter is non-zero, this function assumes that the 
-** process is complete.  If nFin is zero, it is assumed that
+** caller will keep calling incrVacuumStep() until it returns SQLITE_DONE 
-** incrVacuumStep() will be called a finite amount of times
+** or an error. bCommit is passed true for an auto-vacuum-on-commmit 
-** which may or may not empty the freelist.  A full autovacuum
+** operation, or false for an incremental vacuum.
-** has nFin>0.  A "PRAGMA incremental_vacuum" has nFin==0.
 */
-static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
+static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg, int bCommit){
   Pgno nFreeList;           /* Number of pages still on the free-list */
   int rc;
 
@@ -2953,15 +2955,15 @@ static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
     }
 
     if( eType==PTRMAP_FREEPAGE ){
-      if( nFin==0 ){
+      if( bCommit==0 ){
         /* Remove the page from the files free-list. This is not required
-        ** if nFin is non-zero. In that case, the free-list will be
+        ** if bCommit is non-zero. In that case, the free-list will be
         ** truncated to zero after this function returns, so it doesn't 
         ** matter if it still contains some garbage entries.
         */
         Pgno iFreePg;
         MemPage *pFreePg;
-        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, 1);
+        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iLastPg, BTALLOC_EXACT);
         if( rc!=SQLITE_OK ){
           return rc;
         }
@@ -2971,28 +2973,34 @@ static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
     } else {
       Pgno iFreePg;             /* Index of free page to move pLastPg to */
       MemPage *pLastPg;
+      u8 eMode = BTALLOC_ANY;   /* Mode parameter for allocateBtreePage() */
+      Pgno iNear = 0;           /* nearby parameter for allocateBtreePage() */
 
       rc = btreeGetPage(pBt, iLastPg, &pLastPg, 0);
       if( rc!=SQLITE_OK ){
         return rc;
       }
 
-      /* If nFin is zero, this loop runs exactly once and page pLastPg
+      /* If bCommit is zero, this loop runs exactly once and page pLastPg
       ** is swapped with the first free page pulled off the free list.
       **
-      ** On the other hand, if nFin is greater than zero, then keep
+      ** On the other hand, if bCommit is greater than zero, then keep
       ** looping until a free-page located within the first nFin pages
       ** of the file is found.
       */
+      if( bCommit==0 ){
+        eMode = BTALLOC_LE;
+        iNear = nFin;
+      }
       do {
         MemPage *pFreePg;
-        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, 0, 0);
+        rc = allocateBtreePage(pBt, &pFreePg, &iFreePg, iNear, eMode);
         if( rc!=SQLITE_OK ){
           releasePage(pLastPg);
           return rc;
         }
         releasePage(pFreePg);
-      }while( nFin!=0 && iFreePg>nFin );
+      }while( bCommit && iFreePg>nFin );
       assert( iFreePg<iLastPg );
       
       rc = sqlite3PagerWrite(pLastPg->pDbPage);
@@ -3006,7 +3014,7 @@ static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
     }
   }
 
-  if( nFin==0 ){
+  if( bCommit==0 ){
     iLastPg--;
     while( iLastPg==PENDING_BYTE_PAGE(pBt)||PTRMAP_ISPAGE(pBt, iLastPg) ){
       if( PTRMAP_ISPAGE(pBt, iLastPg) ){
@@ -3029,6 +3037,30 @@ static int incrVacuumStep(BtShared *pBt, Pgno nFin, Pgno iLastPg){
   return SQLITE_OK;
 }
 
+/*
+** The database opened by the first argument is an auto-vacuum database
+** nOrig pages in size containing nFree free pages. Return the expected 
+** size of the database in pages following an auto-vacuum operation.
+*/
+static Pgno finalDbSize(BtShared *pBt, Pgno nOrig, Pgno nFree){
+  int nEntry;                     /* Number of entries on one ptrmap page */
+  Pgno nPtrmap;                   /* Number of PtrMap pages to be freed */
+  Pgno nFin;                      /* Return value */
+
+  nEntry = pBt->usableSize/5;
+  nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
+  nFin = nOrig - nFree - nPtrmap;
+  if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
+    nFin--;
+  }
+  while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
+    nFin--;
+  }
+  if( nFin>nOrig ) return SQLITE_CORRUPT_BKPT;
+
+  return nFin;
+}
+
 /*
 ** A write-transaction must be opened before calling this function.
 ** It performs a single unit of work towards an incremental vacuum.
@@ -3046,12 +3078,20 @@ int sqlite3BtreeIncrVacuum(Btree *p){
   if( !pBt->autoVacuum ){
     rc = SQLITE_DONE;
   }else{
+    Pgno nOrig = btreePagecount(pBt);
+    Pgno nFree = get4byte(&pBt->pPage1->aData[36]);
+    Pgno nFin = finalDbSize(pBt, nOrig, nFree);
+
+    if( nFin<nOrig ){
       invalidateAllOverflowCache(pBt);
-    rc = incrVacuumStep(pBt, 0, btreePagecount(pBt));
+      rc = incrVacuumStep(pBt, nFin, nOrig, 0);
       if( rc==SQLITE_OK ){
         rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
         put4byte(&pBt->pPage1->aData[28], pBt->nPage);
       }
+    }else{
+      rc = SQLITE_DONE;
+    }
   }
   sqlite3BtreeLeave(p);
   return rc;
@@ -3077,9 +3117,7 @@ static int autoVacuumCommit(BtShared *pBt){
   if( !pBt->incrVacuum ){
     Pgno nFin;         /* Number of pages in database after autovacuuming */
     Pgno nFree;        /* Number of pages on the freelist initially */
-    Pgno nPtrmap;      /* Number of PtrMap pages to be freed */
     Pgno iFree;        /* The next page to be freed */
-    int nEntry;        /* Number of entries on one ptrmap page */
     Pgno nOrig;        /* Database size before freeing */
 
     nOrig = btreePagecount(pBt);
@@ -3092,19 +3130,11 @@ static int autoVacuumCommit(BtShared *pBt){
     }
 
     nFree = get4byte(&pBt->pPage1->aData[36]);
-    nEntry = pBt->usableSize/5;
+    nFin = finalDbSize(pBt, nOrig, nFree);
-    nPtrmap = (nFree-nOrig+PTRMAP_PAGENO(pBt, nOrig)+nEntry)/nEntry;
-    nFin = nOrig - nFree - nPtrmap;
-    if( nOrig>PENDING_BYTE_PAGE(pBt) && nFin<PENDING_BYTE_PAGE(pBt) ){
-      nFin--;
-    }
-    while( PTRMAP_ISPAGE(pBt, nFin) || nFin==PENDING_BYTE_PAGE(pBt) ){
-      nFin--;
-    }
     if( nFin>nOrig ) return SQLITE_CORRUPT_BKPT;
 
     for(iFree=nOrig; iFree>nFin && rc==SQLITE_OK; iFree--){
-      rc = incrVacuumStep(pBt, nFin, iFree);
+      rc = incrVacuumStep(pBt, nFin, iFree, 1);
     }
     if( (rc==SQLITE_DONE || rc==SQLITE_OK) && nFree>0 ){
       rc = sqlite3PagerWrite(pBt->pPage1->pDbPage);
@@ -4867,7 +4897,7 @@ static int allocateBtreePage(
   MemPage **ppPage, 
   Pgno *pPgno, 
   Pgno nearby,
-  u8 exact
+  u8 eMode
 ){
   MemPage *pPage1;
   int rc;
@@ -4895,7 +4925,8 @@ static int allocateBtreePage(
     ** the entire-list will be searched for that page.
     */
 #ifndef SQLITE_OMIT_AUTOVACUUM
-    if( exact && nearby<=mxPage ){
+    if( eMode==BTALLOC_EXACT ){
+      if( nearby<=mxPage ){
         u8 eType;
         assert( nearby>0 );
         assert( pBt->autoVacuum );
@@ -4904,7 +4935,9 @@ static int allocateBtreePage(
         if( eType==PTRMAP_FREEPAGE ){
           searchList = 1;
         }
-      *pPgno = nearby;
+      }
+    }else if( eMode==BTALLOC_LE ){
+      searchList = 1;
     }
 #endif
 
@@ -4959,11 +4992,13 @@ static int allocateBtreePage(
         rc = SQLITE_CORRUPT_BKPT;
         goto end_allocate_page;
 #ifndef SQLITE_OMIT_AUTOVACUUM
-      }else if( searchList && nearby==iTrunk ){
+      }else if( searchList 
+            && (nearby==iTrunk || (iTrunk<nearby && eMode==BTALLOC_LE)) 
+      ){
         /* The list is being searched and this trunk page is the page
         ** to allocate, regardless of whether it has leaves.
         */
-        assert( *pPgno==iTrunk );
+        *pPgno = iTrunk;
         *ppPage = pTrunk;
         searchList = 0;
         rc = sqlite3PagerWrite(pTrunk->pDbPage);
@@ -5047,7 +5082,9 @@ static int allocateBtreePage(
           goto end_allocate_page;
         }
         testcase( iPage==mxPage );
-        if( !searchList || iPage==nearby ){
+        if( !searchList 
+         || (iPage==nearby || (iPage<nearby && eMode==BTALLOC_LE)) 
+        ){
           int noContent;
           *pPgno = iPage;
           TRACE(("ALLOCATE: %d was leaf %d of %d on trunk %d"
@@ -7119,7 +7156,7 @@ static int btreeCreateTable(Btree *p, int *piTable, int createTabFlags){
     ** be moved to the allocated page (unless the allocated page happens
     ** to reside at pgnoRoot).
     */
-    rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, 1);
+    rc = allocateBtreePage(pBt, &pPageMove, &pgnoMove, pgnoRoot, BTALLOC_EXACT);
     if( rc!=SQLITE_OK ){
       return rc;
     }