Avoid storing the result register for EXISTS and SELECT in any field of

the Expr object - simply return the register number as the return value
of the function that codes those expressions.

FossilOrigin-Name: 7253f8fad1efe6b88666f0f8740d247ff07a7640

manifest

@@ -1,8 +1,8 @@
 -----BEGIN PGP SIGNED MESSAGE-----
 Hash: SHA1
 
-C Reduce\sthe\smemory\srequired\sby\sprepared\sstatements\sthat\suse\sthe\sIN\soperator\s\nwith\sa\slist\son\sthe\sright\sand\san\sINTEGER\sPRIMARY\sKEY\son\sthe\sleft.
-D 2009-10-29T13:48:11
+C Avoid\sstoring\sthe\sresult\sregister\sfor\sEXISTS\sand\sSELECT\sin\sany\sfield\sof\nthe\sExpr\sobject\s-\ssimply\sreturn\sthe\sregister\snumber\sas\sthe\sreturn\svalue\nof\sthe\sfunction\sthat\scodes\sthose\sexpressions.
+D 2009-10-30T13:25:57
 F Makefile.arm-wince-mingw32ce-gcc fcd5e9cd67fe88836360bb4f9ef4cb7f8e2fb5a0
 F Makefile.in a77dfde96ad86aafd3f71651a4333a104debe86a
 F Makefile.linux-gcc d53183f4aa6a9192d249731c90dbdffbd2c68654
@@ -117,7 +117,7 @@ F src/callback.c 10d237171472865f58fb07d515737238c9e06688
 F src/complete.c 5ad5c6cd4548211867c204c41a126d73a9fbcea0
 F src/date.c 657ff12ca0f1195b531561afacbb38b772d16638
 F src/delete.c 308e300d599d2d11b838687e2cf7309d42f29a1a
-F src/expr.c 658002e35de61e9a769a3bc438cc457171cbab17
+F src/expr.c 26dc693216dfafbdde18de2269cc00a627b7807b
 F src/fault.c dc88c821842157460750d2d61a8a8b4197d047ff
 F src/fkey.c 41219cba186bcf0a053e42327dfa23aaba4f834a
 F src/func.c e536218d193b8d326aab91120bc4c6f28aa2b606
@@ -167,7 +167,7 @@ F src/select.c cbe366a0ce114856e66f5daf0f848d7c48a88298
 F src/shell.c f66531a57fff927f95c98d99c28237d88e400c86
 F src/sqlite.h.in 5853e42a4066a6c9c3bf6592a9d57d0012bfdb90
 F src/sqlite3ext.h 1db7d63ab5de4b3e6b83dd03d1a4e64fef6d2a17
-F src/sqliteInt.h 3b00a3ce79e60c5a47c342b738c8b75013f3ec84
+F src/sqliteInt.h 00256600cb4e17d71373df3844aa53aed5594cdb
 F src/sqliteLimit.h 38b2fffcd01faeaeaadea71b2b47695a81580c8b
 F src/status.c 237b193efae0cf6ac3f0817a208de6c6c6ef6d76
 F src/table.c cc86ad3d6ad54df7c63a3e807b5783c90411a08d
@@ -764,14 +764,14 @@ F tool/speedtest2.tcl ee2149167303ba8e95af97873c575c3e0fab58ff
 F tool/speedtest8.c 2902c46588c40b55661e471d7a86e4dd71a18224
 F tool/speedtest8inst1.c 293327bc76823f473684d589a8160bde1f52c14e
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
-P ad949fa1acb4546fe4f2a448025579cc374dd8dd
-R 3bb532253075d93fd9eb68f8cb42f41d
+P e7984ad2f7e4be30e7198ebd6609a7f6177513e2
+R cd38913b285f7c9e4491c7e2f4bd28f3
 U drh
-Z db24204c5eebb100574fed36b2374757
+Z f2bea1211055544cac6d8aed3a82cf0f
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-=dwzc
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manifest.uuid

@@ -1 +1 @@
-e7984ad2f7e4be30e7198ebd6609a7f6177513e2
+7253f8fad1efe6b88666f0f8740d247ff07a7640

src/expr.c

@@ -1372,6 +1372,8 @@ int sqlite3FindInIndex(Parse *pParse, Expr *pX, int *prNotFound){
   int iTab = pParse->nTab++;            /* Cursor of the RHS table */
   int mustBeUnique = (prNotFound==0);   /* True if RHS must be unique */
 
+  assert( pX->op==TK_IN );
+
   /* Check to see if an existing table or index can be used to
   ** satisfy the query.  This is preferable to generating a new 
   ** ephemeral table.
@@ -1449,7 +1451,7 @@ int sqlite3FindInIndex(Parse *pParse, Expr *pX, int *prNotFound){
   }
 
   if( eType==0 ){
-    /* Could not found an existing able or index to use as the RHS b-tree.
+    /* Could not found an existing table or index to use as the RHS b-tree.
     ** We will have to generate an ephemeral table to do the job.
     */
     int rMayHaveNull = 0;
@@ -1496,17 +1498,21 @@ int sqlite3FindInIndex(Parse *pParse, Expr *pX, int *prNotFound){
 ** If rMayHaveNull is zero, that means that the subquery is being used
 ** for membership testing only.  There is no need to initialize any
 ** registers to indicate the presense or absence of NULLs on the RHS.
+**
+** For a SELECT or EXISTS operator, return the register that holds the
+** result.  For IN operators or if an error occurs, the return value is 0.
 */
 #ifndef SQLITE_OMIT_SUBQUERY
-void sqlite3CodeSubselect(
+int sqlite3CodeSubselect(
   Parse *pParse,          /* Parsing context */
   Expr *pExpr,            /* The IN, SELECT, or EXISTS operator */
   int rMayHaveNull,       /* Register that records whether NULLs exist in RHS */
   int isRowid             /* If true, LHS of IN operator is a rowid */
 ){
   int testAddr = 0;                       /* One-time test address */
+  int rReg = 0;                           /* Register storing resulting */
   Vdbe *v = sqlite3GetVdbe(pParse);
-  if( NEVER(v==0) ) return;
+  if( NEVER(v==0) ) return 0;
   sqlite3ExprCachePush(pParse);
 
   /* This code must be run in its entirety every time it is encountered
@@ -1571,7 +1577,7 @@ void sqlite3CodeSubselect(
         dest.affinity = (u8)affinity;
         assert( (pExpr->iTable&0x0000FFFF)==pExpr->iTable );
         if( sqlite3Select(pParse, pExpr->x.pSelect, &dest) ){
-          return;
+          return 0;
         }
         pEList = pExpr->x.pSelect->pEList;
         if( ALWAYS(pEList!=0 && pEList->nExpr>0) ){ 
@@ -1671,9 +1677,9 @@ void sqlite3CodeSubselect(
       sqlite3ExprDelete(pParse->db, pSel->pLimit);
       pSel->pLimit = sqlite3PExpr(pParse, TK_INTEGER, 0, 0, &one);
       if( sqlite3Select(pParse, pSel, &dest) ){
-        return;
+        return 0;
       }
-      pExpr->iColumn = (i16)dest.iParm;
+      rReg = dest.iParm;
       ExprSetIrreducible(pExpr);
       break;
     }
@@ -1684,7 +1690,7 @@ void sqlite3CodeSubselect(
   }
   sqlite3ExprCachePop(pParse, 1);
 
-  return;
+  return rReg;
 }
 #endif /* SQLITE_OMIT_SUBQUERY */
 
@@ -2441,8 +2447,7 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
     case TK_SELECT: {
       testcase( op==TK_EXISTS );
       testcase( op==TK_SELECT );
-      sqlite3CodeSubselect(pParse, pExpr, 0, 0);
-      inReg = pExpr->iColumn;
+      inReg = sqlite3CodeSubselect(pParse, pExpr, 0, 0);
       break;
     }
     case TK_IN: {

src/sqliteInt.h

@@ -2841,7 +2841,7 @@ void sqlite3AlterRenameTable(Parse*, SrcList*, Token*);
 int sqlite3GetToken(const unsigned char *, int *);
 void sqlite3NestedParse(Parse*, const char*, ...);
 void sqlite3ExpirePreparedStatements(sqlite3*);
-void sqlite3CodeSubselect(Parse *, Expr *, int, int);
+int sqlite3CodeSubselect(Parse *, Expr *, int, int);
 void sqlite3SelectPrep(Parse*, Select*, NameContext*);
 int sqlite3ResolveExprNames(NameContext*, Expr*);
 void sqlite3ResolveSelectNames(Parse*, Select*, NameContext*);