Simplify and improve the performance of the sqlite3VdbeMemGrow() routine.

FossilOrigin-Name: 48ecf18774ba9572d86696c60d87007a619d9f53

manifest

@@ -1,5 +1,5 @@
-C Simplifications\sto\sthe\sOP_MakeRecord\sopcode\sand\sthe\ssqlite3VdbeSerialPut()\nhelper\sfunction.
-D 2013-12-09T23:17:22.886
+C Simplify\sand\simprove\sthe\sperformance\sof\sthe\ssqlite3VdbeMemGrow()\sroutine.
+D 2013-12-10T19:49:00.802
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in e1a9b4258bbde53f5636f4e238c65b7e11459e2b
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -188,8 +188,8 @@ F src/journal.c b4124532212b6952f42eb2c12fa3c25701d8ba8d
 F src/legacy.c 0df0b1550b9cc1f58229644735e317ac89131f12
 F src/lempar.c cdf0a000315332fc9b50b62f3b5e22e080a0952b
 F src/loadext.c 867c7b330b740c6c917af9956b13b81d0a048303
-F src/main.c 355fc9ab213b43a4d8a96aadf2a84622e6668f0a
-F src/malloc.c 543a8eb5508eaf4cadf55a9b503379eba2088128
+F src/main.c a79c8ca051a914e50d6b221d56801d47835714d8
+F src/malloc.c 0203ebce9152c6a0e5de520140b8ba65187350be
 F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c c0c990fcaddff810ea277b4fb5d9138603dd5d4b
 F src/mem2.c dce31758da87ec2cfa52ba4c5df1aed6e07d8e8f
@@ -286,7 +286,7 @@ F src/vdbeInt.h 7e38eef8f4bd7141e1638b0eacaebf9bc41b26bc
 F src/vdbeapi.c 93a22a9ba2abe292d5c2cf304d7eb2e894dde0ed
 F src/vdbeaux.c d64bc2a057e77aef3e2a4bc6670b80f516a36d55
 F src/vdbeblob.c 8cd05a5630e6d5563ad017bf82edaf812b28acde
-F src/vdbemem.c 2293b66374f4adf54bbdcd662c05a003318600e1
+F src/vdbemem.c a381254caef0d102b091923a309c4c3a06a65393
 F src/vdbesort.c 9d83601f9d6243fe70dd0169a2820c5ddfd48147
 F src/vdbetrace.c e7ec40e1999ff3c6414424365d5941178966dcbc
 F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
@@ -1146,7 +1146,7 @@ F tool/vdbe-compress.tcl f12c884766bd14277f4fcedcae07078011717381
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
-P c43b59dac1fbb67ec3a9d921005543046ad416ce
-R c11616a6774c1e84bdec6602d7be1c45
+P 7277a769694787e0332d1a4efc02041834661e2a
+R 3ef0e61f6611b17b108322b8d504b195
 U drh
-Z 4d30567758bc854237be3d93d5ebeaed
+Z 641e108686357e5c2dc6bc5a433b2dd9

manifest.uuid

@@ -1 +1 @@
-7277a769694787e0332d1a4efc02041834661e2a
+48ecf18774ba9572d86696c60d87007a619d9f53

src/main.c

@@ -588,7 +588,8 @@ static int setupLookaside(sqlite3 *db, void *pBuf, int sz, int cnt){
     db->lookaside.bEnabled = 1;
     db->lookaside.bMalloced = pBuf==0 ?1:0;
   }else{
-    db->lookaside.pEnd = 0;
+    db->lookaside.pStart = db;
+    db->lookaside.pEnd = db;
     db->lookaside.bEnabled = 0;
     db->lookaside.bMalloced = 0;
   }

src/malloc.c

@@ -433,7 +433,7 @@ void sqlite3ScratchFree(void *p){
 */
 #ifndef SQLITE_OMIT_LOOKASIDE
 static int isLookaside(sqlite3 *db, void *p){
-  return p && p>=db->lookaside.pStart && p<db->lookaside.pEnd;
+  return p>=db->lookaside.pStart && p<db->lookaside.pEnd;
 }
 #else
 #define isLookaside(A,B) 0
@@ -449,8 +449,9 @@ int sqlite3MallocSize(void *p){
   return sqlite3GlobalConfig.m.xSize(p);
 }
 int sqlite3DbMallocSize(sqlite3 *db, void *p){
-  assert( db==0 || sqlite3_mutex_held(db->mutex) );
-  if( db && isLookaside(db, p) ){
+  assert( db!=0 );
+  assert( sqlite3_mutex_held(db->mutex) );
+  if( isLookaside(db, p) ){
     return db->lookaside.sz;
   }else{
     assert( sqlite3MemdebugHasType(p, MEMTYPE_DB) );

src/vdbemem.c

@@ -59,18 +59,14 @@ int sqlite3VdbeChangeEncoding(Mem *pMem, int desiredEnc){
 
 /*
 ** Make sure pMem->z points to a writable allocation of at least 
-** n bytes.
+** min(n,32) bytes.
 **
-** If the third argument passed to this function is true, then memory
-** cell pMem must contain a string or blob. In this case the content is
-** preserved. Otherwise, if the third parameter to this function is false,
-** any current string or blob value may be discarded.
-**
-** This function sets the MEM_Dyn flag and clears any xDel callback.
-** It also clears MEM_Ephem and MEM_Static. If the preserve flag is 
-** not set, Mem.n is zeroed.
+** If the bPreserve argument is true, then copy of the content of
+** pMem->z into the new allocation.  pMem must be either a string or
+** blob if bPreserve is true.  If bPreserve is false, any prior content
+** in pMem->z is discarded.
 */
-int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve){
+int sqlite3VdbeMemGrow(Mem *pMem, int n, int bPreserve){
   assert( 1 >=
     ((pMem->zMalloc && pMem->zMalloc==pMem->z) ? 1 : 0) +
     (((pMem->flags&MEM_Dyn)&&pMem->xDel) ? 1 : 0) + 
@@ -79,37 +75,39 @@ int sqlite3VdbeMemGrow(Mem *pMem, int n, int preserve){
   );
   assert( (pMem->flags&MEM_RowSet)==0 );
 
-  /* If the preserve flag is set to true, then the memory cell must already
+  /* If the bPreserve flag is set to true, then the memory cell must already
   ** contain a valid string or blob value.  */
-  assert( preserve==0 || pMem->flags&(MEM_Blob|MEM_Str) );
+  assert( bPreserve==0 || pMem->flags&(MEM_Blob|MEM_Str) );
+  testcase( bPreserve && pMem->z==0 );
 
-  if( n<32 ) n = 32;
-  if( sqlite3DbMallocSize(pMem->db, pMem->zMalloc)<n ){
-    if( preserve && pMem->z==pMem->zMalloc ){
+  if( pMem->zMalloc==0 || sqlite3DbMallocSize(pMem->db, pMem->zMalloc)<n ){
+    if( n<32 ) n = 32;
+    if( bPreserve && pMem->z==pMem->zMalloc ){
       pMem->z = pMem->zMalloc = sqlite3DbReallocOrFree(pMem->db, pMem->z, n);
-      preserve = 0;
+      bPreserve = 0;
     }else{
       sqlite3DbFree(pMem->db, pMem->zMalloc);
       pMem->zMalloc = sqlite3DbMallocRaw(pMem->db, n);
     }
+    if( pMem->zMalloc==0 ){
+      sqlite3VdbeMemRelease(pMem);
+      pMem->flags = MEM_Null;  
+      return SQLITE_NOMEM;
+    }
   }
 
-  if( pMem->z && preserve && pMem->zMalloc && pMem->z!=pMem->zMalloc ){
+  if( pMem->z && bPreserve && pMem->z!=pMem->zMalloc ){
     memcpy(pMem->zMalloc, pMem->z, pMem->n);
   }
-  if( pMem->flags&MEM_Dyn && pMem->xDel ){
+  if( (pMem->flags&MEM_Dyn)!=0 && pMem->xDel ){
     assert( pMem->xDel!=SQLITE_DYNAMIC );
     pMem->xDel((void *)(pMem->z));
   }
 
   pMem->z = pMem->zMalloc;
-  if( pMem->z==0 ){
-    pMem->flags = MEM_Null;
-  }else{
-    pMem->flags &= ~(MEM_Ephem|MEM_Static);
-  }
+  pMem->flags &= ~(MEM_Ephem|MEM_Static);
   pMem->xDel = 0;
-  return (pMem->z ? SQLITE_OK : SQLITE_NOMEM);
+  return SQLITE_OK;
 }
 
 /*