Modify the integrity-check code to reduce the size of the large allocation from 4 bytes to 1 bit for each page in the database file.

FossilOrigin-Name: fa3a498dfe9ed59c30da5eaa0d7cad167fd4e393

manifest

@@ -1,5 +1,5 @@
-C Fix\sa\stypo\sin\sthe\srtree6.test\sscript\sthat\sprevented\sit\sfrom\srunning.
-D 2012-04-03T17:05:16.797
+C Modify\sthe\sintegrity-check\scode\sto\sreduce\sthe\ssize\sof\sthe\slarge\sallocation\sfrom\s4\sbytes\sto\s1\sbit\sfor\seach\spage\sin\sthe\sdatabase\sfile.
+D 2012-04-03T17:43:28.322
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 2f37e468503dbe79d35c9f6dffcf3fae1ae9ec20
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -126,9 +126,9 @@ F src/auth.c 523da7fb4979469955d822ff9298352d6b31de34
 F src/backup.c 6be23a344d3301ae38e92fddb3a33b91c309fce4
 F src/bitvec.c af50f1c8c0ff54d6bdb7a80e2fceca5a93670bef
 F src/btmutex.c 976f45a12e37293e32cae0281b15a21d48a8aaa7
-F src/btree.c 02aeee1f6d425e11f7b9b2d9d461ac501645ed6f
+F src/btree.c df800f10896bc2ddaa1125c532d6e7a7b9efc532
 F src/btree.h 48a013f8964f12d944d90e4700df47b72dd6d923
-F src/btreeInt.h 26d8ca625b141927fe6620c1d2cf58eaf494ca0c
+F src/btreeInt.h 38a639c0542c29fe8331a221c4aed0cb8686249e
 F src/build.c 987c6933ea170e443dc6a79d52f8d2506206b12b
 F src/callback.c 0425c6320730e6d3981acfb9202c1bed9016ad1a
 F src/complete.c dc1d136c0feee03c2f7550bafc0d29075e36deac
@@ -1000,7 +1000,7 @@ F tool/tostr.awk e75472c2f98dd76e06b8c9c1367f4ab07e122d06
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
 F tool/warnings-clang.sh 9f406d66e750e8ac031c63a9ef3248aaa347ef2a
 F tool/warnings.sh fbc018d67fd7395f440c28f33ef0f94420226381
-P 6d73eb20e825f51143a1b59ad33f44e6448ef760
-R 1bfa9697c3ee58e945b220e1f2e117e6
-U drh
-Z 04df2a29417f5db40a26641a7a738bb8
+P 221fe4a8ea5bea90031e459746ea71ff173e6f52
+R 32aad9893eefdebd852afcbce9893d62
+U dan
+Z 24eef38a1ddea33d5b3c726c6b9516d2

manifest.uuid

@@ -1 +1 @@
-221fe4a8ea5bea90031e459746ea71ff173e6f52
+fa3a498dfe9ed59c30da5eaa0d7cad167fd4e393

src/btree.c

@@ -7554,6 +7554,25 @@ static void checkAppendMsg(
 #endif /* SQLITE_OMIT_INTEGRITY_CHECK */
 
 #ifndef SQLITE_OMIT_INTEGRITY_CHECK
+
+/*
+** Return non-zero if the bit in the IntegrityCk.aPgRef[] array that
+** corresponds to page iPg is already set.
+*/
+static int getPageReferenced(IntegrityCk *pCheck, Pgno iPg){
+  assert( iPg<=pCheck->nPage && sizeof(pCheck->aPgRef[0])==1 );
+  return (pCheck->aPgRef[iPg/8] & (1 << (iPg & 0x07)));
+}
+
+/*
+** Set the bit in the IntegrityCk.aPgRef[] array that corresponds to page iPg.
+*/
+static void setPageReferenced(IntegrityCk *pCheck, Pgno iPg){
+  assert( iPg<=pCheck->nPage && sizeof(pCheck->aPgRef[0])==1 );
+  pCheck->aPgRef[iPg/8] |= (1 << (iPg & 0x07));
+}
+
+
 /*
 ** Add 1 to the reference count for page iPage.  If this is the second
 ** reference to the page, add an error message to pCheck->zErrMsg.
@@ -7568,11 +7587,12 @@ static int checkRef(IntegrityCk *pCheck, Pgno iPage, char *zContext){
     checkAppendMsg(pCheck, zContext, "invalid page number %d", iPage);
     return 1;
   }
-  if( pCheck->anRef[iPage]==1 ){
+  if( getPageReferenced(pCheck, iPage) ){
     checkAppendMsg(pCheck, zContext, "2nd reference to page %d", iPage);
     return 1;
   }
-  return  (pCheck->anRef[iPage]++)>1;
+  setPageReferenced(pCheck, iPage);
+  return 0;
 }
 
 #ifndef SQLITE_OMIT_AUTOVACUUM
@@ -7948,17 +7968,15 @@ char *sqlite3BtreeIntegrityCheck(
     sqlite3BtreeLeave(p);
     return 0;
   }
-  sCheck.anRef = sqlite3Malloc( (sCheck.nPage+1)*sizeof(sCheck.anRef[0]) );
-  if( !sCheck.anRef ){
+
+  sCheck.aPgRef = sqlite3MallocZero((sCheck.nPage / 8)+ 1);
+  if( !sCheck.aPgRef ){
     *pnErr = 1;
     sqlite3BtreeLeave(p);
     return 0;
   }
-  for(i=0; i<=sCheck.nPage; i++){ sCheck.anRef[i] = 0; }
   i = PENDING_BYTE_PAGE(pBt);
-  if( i<=sCheck.nPage ){
-    sCheck.anRef[i] = 1;
-  }
+  if( i<=sCheck.nPage ) setPageReferenced(&sCheck, i);
   sqlite3StrAccumInit(&sCheck.errMsg, zErr, sizeof(zErr), 20000);
   sCheck.errMsg.useMalloc = 2;
 
@@ -7983,18 +8001,18 @@ char *sqlite3BtreeIntegrityCheck(
   */
   for(i=1; i<=sCheck.nPage && sCheck.mxErr; i++){
 #ifdef SQLITE_OMIT_AUTOVACUUM
-    if( sCheck.anRef[i]==0 ){
+    if( getPageReferenced(&sCheck, i)==0 ){
       checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
     }
 #else
     /* If the database supports auto-vacuum, make sure no tables contain
     ** references to pointer-map pages.
     */
-    if( sCheck.anRef[i]==0 && 
+    if( getPageReferenced(&sCheck, i)==0 && 
        (PTRMAP_PAGENO(pBt, i)!=i || !pBt->autoVacuum) ){
       checkAppendMsg(&sCheck, 0, "Page %d is never used", i);
     }
-    if( sCheck.anRef[i]!=0 && 
+    if( getPageReferenced(&sCheck, i)!=0 && 
        (PTRMAP_PAGENO(pBt, i)==i && pBt->autoVacuum) ){
       checkAppendMsg(&sCheck, 0, "Pointer map page %d is referenced", i);
     }
@@ -8015,7 +8033,7 @@ char *sqlite3BtreeIntegrityCheck(
   /* Clean  up and report errors.
   */
   sqlite3BtreeLeave(p);
-  sqlite3_free(sCheck.anRef);
+  sqlite3_free(sCheck.aPgRef);
   if( sCheck.mallocFailed ){
     sqlite3StrAccumReset(&sCheck.errMsg);
     *pnErr = sCheck.nErr+1;

src/btreeInt.h

@@ -631,12 +631,18 @@ struct BtCursor {
 /*
 ** This structure is passed around through all the sanity checking routines
 ** in order to keep track of some global state information.
+**
+** The aRef[] array is allocated so that there is 1 bit for each page in
+** the database. As the integrity-check proceeds, for each page used in
+** the database the corresponding bit is set. This allows integrity-check to 
+** detect pages that are used twice and orphaned pages (both of which 
+** indicate corruption).
 */
 typedef struct IntegrityCk IntegrityCk;
 struct IntegrityCk {
   BtShared *pBt;    /* The tree being checked out */
   Pager *pPager;    /* The associated pager.  Also accessible by pBt->pPager */
-  int *anRef;       /* Number of times each page is referenced */
+  u8 *aPgRef;       /* 1 bit per page in the db (see above) */
   Pgno nPage;       /* Number of pages in the database */
   int mxErr;        /* Stop accumulating errors when this reaches zero */
   int nErr;         /* Number of messages written to zErrMsg so far */