Avoid unnecessary Mem initializations when generating a new sqlite3_stmt

object.

FossilOrigin-Name: 47ae1cda8dc255d100aeb8cb90ea4c9e449509be

manifest

@@ -1,5 +1,5 @@
-C Small\ssize\sand\sperformance\soptimization\sto\ssqlite3VdbeChangeP5().
+C Avoid\sunnecessary\sMem\sinitializations\swhen\sgenerating\sa\snew\ssqlite3_stmt\nobject.
-D 2016-09-29T20:28:34.145
+D 2016-09-30T17:46:44.827
 F Makefile.in 6fd48ffcf7c2deea7499062d1f3747f986c19678
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 5151cc64c4c05f3455f4f692ad11410a810d937f
@@ -453,13 +453,13 @@ F src/update.c 8179e699dbd45b92934fd02d3d8e3732e8da8802
 F src/utf.c 699001c79f28e48e9bcdf8a463da029ea660540c
 F src/util.c 3e2da6101888d073e79ecc6af5e0a2f70fa1e498
 F src/vacuum.c 913970b9d86dd6c2b8063ef1af421880f1464ec3
-F src/vdbe.c 6781329737f4bb140834cd32b15e93b83d60858e
+F src/vdbe.c 51e754eec26d892abc6279f5e949545af68ec1b3
 F src/vdbe.h c044be7050ac6bf596eecc6ab159f5dbc020a3b7
 F src/vdbeInt.h 581b737c2f6e413c555469480efe31796a71bcad
 F src/vdbeapi.c 794f80669e9e3b9b3edc78d80c15968985c7bf21
-F src/vdbeaux.c 041dd9dd28dfe57dc0104a98c067cadd808a059c
+F src/vdbeaux.c 240fecf157b6a3deb3c68abe614ae30cb8e884cd
 F src/vdbeblob.c 3e82a797b60c3b9fed7b8de8c539ca7607874937
-F src/vdbemem.c 1b8d5b770a9a3c6d8ed3463104a382bffa6f15c2
+F src/vdbemem.c 1c330522e6b6e4ddd2ff63c4c0dfafa20c3965a7
 F src/vdbesort.c 91fda3909326860382b0ca8aa251e609c6a9d62c
 F src/vdbetrace.c 41963d5376f0349842b5fc4aaaaacd7d9cdc0834
 F src/vtab.c e02cacb5c7ae742631edeb9ae9f53d399f093fd8
@@ -1525,7 +1525,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 984a96d79656c1b095aba1f88aca4bb787ba0bd8
+P 3c93c8f5bbf54ed2a331079b28fdd94eb0e59e69
-R 6df17638e558d58efae8855e65d389dc
+R 3cf19b11ac694d678c7ce4092749d94e
 U drh
-Z 789252daa215e2c9b52dcdaab286dc1e
+Z 262005117be631ec889db38469ab8967

manifest.uuid

@@ -1 +1 @@
-3c93c8f5bbf54ed2a331079b28fdd94eb0e59e69
+47ae1cda8dc255d100aeb8cb90ea4c9e449509be

src/vdbe.c

@@ -1136,11 +1136,13 @@ case OP_Null: {           /* out2 */
   cnt = pOp->p3-pOp->p2;
   assert( pOp->p3<=(p->nMem+1 - p->nCursor) );
   pOut->flags = nullFlag = pOp->p1 ? (MEM_Null|MEM_Cleared) : MEM_Null;
+  pOut->n = 0;
   while( cnt>0 ){
     pOut++;
     memAboutToChange(p, pOut);
     sqlite3VdbeMemSetNull(pOut);
     pOut->flags = nullFlag;
+    pOut->n = 0;
     cnt--;
   }
   break;

src/vdbeaux.c

@@ -1458,6 +1458,21 @@ void sqlite3VdbePrintOp(FILE *pOut, int pc, Op *pOp){
 }
 #endif
 
+/*
+** Initialize an array of N Mem element.
+*/
+static void initMemArray(Mem *p, int N, sqlite3 *db, u16 flags){
+  while( (N--)>0 ){
+    p->db = db;
+    p->flags = flags;
+    p->szMalloc = 0;
+#ifdef SQLITE_DEBUG
+    p->pScopyFrom = 0;
+#endif
+    p++;
+  }
+}
+
 /*
 ** Release an array of N Mem elements
 */
@@ -1669,6 +1684,7 @@ int sqlite3VdbeList(
     pMem->flags = MEM_Str|MEM_Term;
     zP4 = displayP4(pOp, pMem->z, pMem->szMalloc);
     if( zP4!=pMem->z ){
+      pMem->n = 0;
       sqlite3VdbeMemSetStr(pMem, zP4, -1, SQLITE_UTF8, 0);
     }else{
       assert( pMem->z!=0 );
@@ -1900,10 +1916,7 @@ void sqlite3VdbeMakeReady(
   assert( EIGHT_BYTE_ALIGNMENT(x.pSpace) );
   x.nFree = ROUNDDOWN8(pParse->szOpAlloc - n);  /* Bytes of unused memory */
   assert( x.nFree>=0 );
-  if( x.nFree>0 ){
+  assert( EIGHT_BYTE_ALIGNMENT(&x.pSpace[x.nFree]) );
-    memset(x.pSpace, 0, x.nFree);
-    assert( EIGHT_BYTE_ALIGNMENT(&x.pSpace[x.nFree]) );
-  }
 
   resolveP2Values(p, &nArg);
   p->usesStmtJournal = (u8)(pParse->isMultiWrite && pParse->mayAbort);
@@ -1932,30 +1945,27 @@ void sqlite3VdbeMakeReady(
     p->anExec = allocSpace(&x, p->anExec, p->nOp*sizeof(i64));
 #endif
     if( x.nNeeded==0 ) break;
-    x.pSpace = p->pFree = sqlite3DbMallocZero(db, x.nNeeded);
+    x.pSpace = p->pFree = sqlite3DbMallocRawNN(db, x.nNeeded);
     x.nFree = x.nNeeded;
   }while( !db->mallocFailed );
 
-  p->nCursor = nCursor;
-  if( p->aVar ){
-    p->nVar = (ynVar)nVar;
-    for(n=0; n<nVar; n++){
-      p->aVar[n].flags = MEM_Null;
-      p->aVar[n].db = db;
-    }
-  }
   p->nzVar = pParse->nzVar;
   p->azVar = pParse->azVar;
   pParse->nzVar =  0;
   pParse->azVar = 0;
-  if( p->aMem ){
-    p->nMem = nMem;
-    for(n=0; n<nMem; n++){
-      p->aMem[n].flags = MEM_Undefined;
-      p->aMem[n].db = db;
-    }
-  }
   p->explain = pParse->explain;
+  if( db->mallocFailed==0 ){
+    p->nCursor = nCursor;
+    p->nVar = (ynVar)nVar;
+    initMemArray(p->aVar, nVar, db, MEM_Null);
+    p->nMem = nMem;
+    initMemArray(p->aMem, nMem, db, MEM_Undefined);
+    memset(p->apArg, 0, nArg*sizeof(Mem*));
+    memset(p->apCsr, 0, nCursor*sizeof(VdbeCursor*));
+#ifdef SQLITE_ENABLE_STMT_SCANSTATUS
+    memset(p->anExec, 0, p->nOp*sizeof(i64));
+#endif
+  }
   sqlite3VdbeRewind(p);
 }
 
@@ -2107,13 +2117,9 @@ void sqlite3VdbeSetNumCols(Vdbe *p, int nResColumn){
   sqlite3DbFree(db, p->aColName);
   n = nResColumn*COLNAME_N;
   p->nResColumn = (u16)nResColumn;
-  p->aColName = pColName = (Mem*)sqlite3DbMallocZero(db, sizeof(Mem)*n );
+  p->aColName = pColName = (Mem*)sqlite3DbMallocRawNN(db, sizeof(Mem)*n );
   if( p->aColName==0 ) return;
-  while( n-- > 0 ){
+  initMemArray(p->aColName, n, p->db, MEM_Null);
-    pColName->flags = MEM_Null;
-    pColName->db = p->db;
-    pColName++;
-  }
 }
 
 /*

src/vdbemem.c

@@ -293,6 +293,7 @@ int sqlite3VdbeMemStringify(Mem *pMem, u8 enc, u8 bForce){
 
 
   if( sqlite3VdbeMemClearAndResize(pMem, nByte) ){
+    pMem->enc = 0;
     return SQLITE_NOMEM_BKPT;
   }