Add logic to the query planner to only use partial indices if the WHERE clause

constrains the search to rows covered by the partial index.  This is just
infrastructure.  The key routine, sqlite3ExprImpliesExpr(), is currently a
no-op so that partial indices will never be used.

FossilOrigin-Name: 8ca3eac111e06a1854f878a74bffe8f20eb47f1b

manifest

@@ -1,5 +1,5 @@
-C Resolve\snames\sin\sCREATE\sINDEX\sWHERE\sclauses\sand\sdetect\serrors.\s\sDisallow\nexpressions\sthat\scontain\svariables,\ssubqueries,\sor\sfunctions.\nThe\sexpression\sis\sstill\snot\sused\sfor\sanything,\showever.\nstill\sunused.
-D 2013-07-31T19:05:22.844
+C Add\slogic\sto\sthe\squery\splanner\sto\sonly\suse\spartial\sindices\sif\sthe\sWHERE\sclause\nconstrains\sthe\ssearch\sto\srows\scovered\sby\sthe\spartial\sindex.\s\sThis\sis\sjust\ninfrastructure.\s\sThe\skey\sroutine,\ssqlite3ExprImpliesExpr(),\sis\scurrently\sa\nno-op\sso\sthat\spartial\sindices\swill\snever\sbe\sused.
+D 2013-07-31T23:22:39.876
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 5e41da95d92656a5004b03d3576e8b226858a28e
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -172,7 +172,7 @@ F src/complete.c dc1d136c0feee03c2f7550bafc0d29075e36deac
 F src/ctime.c 4262c227bc91cecc61ae37ed3a40f08069cfa267
 F src/date.c 067a81c9942c497aafd2c260e13add8a7d0c7dd4
 F src/delete.c aeabdabeeeaa0584127f291baa9617153d334778
-F src/expr.c 2b47ae9da6c9f34eff6736962ea2e102c6c4a755
+F src/expr.c 8a5e78f47c4919bd53c2ef3c652088d71d5c4d79
 F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb
 F src/fkey.c 914a6bbd987d857c41ac9d244efa6641f36faadb
 F src/func.c 5c50c1ea31fd864b0fe921fe1a8d4c55acd609ef
@@ -221,7 +221,7 @@ F src/shell.c 52f975eae87c8338c4dfbf4c2842d2a0971f01fd
 F src/sqlite.h.in d6a7523d6795317aac574fccc67d9df25253771c
 F src/sqlite3.rc fea433eb0a59f4c9393c8e6d76a6e2596b1fe0c0
 F src/sqlite3ext.h 886f5a34de171002ad46fae8c36a7d8051c190fc
-F src/sqliteInt.h ffe632c1de338b459af86e6df712f4583c05b8af
+F src/sqliteInt.h 911e2fe9bbd45c394e6396a1c00a8539285f82e6
 F src/sqliteLimit.h 164b0e6749d31e0daa1a4589a169d31c0dec7b3d
 F src/status.c 7ac05a5c7017d0b9f0b4bcd701228b784f987158
 F src/table.c 2cd62736f845d82200acfa1287e33feb3c15d62e
@@ -290,7 +290,7 @@ F src/vtab.c 2e8b489db47e20ae36cd247932dc671c9ded0624
 F src/wal.c 7dc3966ef98b74422267e7e6e46e07ff6c6eb1b4
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c 4fa43583d0a84b48f93b1e88f11adf2065be4e73
-F src/where.c a55e27475c3d4c72c8bf1aaf9ece70e47e8731cf
+F src/where.c afa338426730378f3d0aa9b24218462b6cca31f3
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
 F test/aggnested.test 45c0201e28045ad38a530b5a144b73cd4aa2cfd6
@@ -1104,7 +1104,7 @@ F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh fbc018d67fd7395f440c28f33ef0f94420226381
 F tool/wherecosttest.c f407dc4c79786982a475261866a161cd007947ae
 F tool/win/sqlite.vsix 97894c2790eda7b5bce3cc79cb2a8ec2fde9b3ac
-P 6794b2dcb48b3507caccfc7867fc185818cf8291
-R 1d2a041bdd5863b9d0e35692b3da5ea5
+P f2aa7842c8b9df24294f09e2bde27b3f08c455c7
+R 7502b7f00f8eb060c8cfe6d979c2a415
 U drh
-Z 96979d6477d3e0c5f80978a86c33129b
+Z 8c5239fd3bb5391973b43192e175e4ae

manifest.uuid

@@ -1 +1 @@
-f2aa7842c8b9df24294f09e2bde27b3f08c455c7
+8ca3eac111e06a1854f878a74bffe8f20eb47f1b

src/expr.c

@@ -3865,6 +3865,26 @@ int sqlite3ExprListCompare(ExprList *pA, ExprList *pB){
   return 0;
 }
 
+/*
+** Return true if we can prove the pE2 will always be true if pE1 is
+** true.  Return false if we cannot complete the proof or if pE2 might
+** be false.  Examples:
+**
+**     pE1: x==5      pE2: x>0              Result: true
+**     pE1: x>0       pE2: x==5             Result: false
+**     pE1: x!=123    pE2: x IS NOT NULL    Result: true
+**
+** When comparing TK_COLUMN nodes between pE1 and pE2, if pE2 has
+** Expr.iTable<0 then assume a table number given by iTab.
+**
+** When in doubt, return false.  Returning true might give a performance
+** improvement.  Returning false might cause a performance reduction, but
+** it will always give the correct answer and is hence always safe.
+*/
+int sqlite3ExprImpliesExpr(Expr *pE1, Expr *pE2, int iTab){
+  return 0;  /* FIXME: this needs to be worked out */
+}
+
 /*
 ** An instance of the following structure is used by the tree walker
 ** to count references to table columns in the arguments of an 

src/sqliteInt.h

@@ -2835,6 +2835,7 @@ int sqlite3RunVacuum(char**, sqlite3*);
 char *sqlite3NameFromToken(sqlite3*, Token*);
 int sqlite3ExprCompare(Expr*, Expr*);
 int sqlite3ExprListCompare(ExprList*, ExprList*);
+int sqlite3ExprImpliesExpr(Expr*, Expr*, int);
 void sqlite3ExprAnalyzeAggregates(NameContext*, Expr*);
 void sqlite3ExprAnalyzeAggList(NameContext*,ExprList*);
 int sqlite3FunctionUsesThisSrc(Expr*, SrcList*);

src/where.c

@@ -4503,6 +4503,17 @@ static Bitmask columnsInIndex(Index *pIdx){
   return m;
 }
 
+/* Check to see if a partial index with pPartIndexWhere can be used
+** in the current query.  Return true if it can be and false if not.
+*/
+static int whereUsablePartialIndex(int iTab, WhereClause *pWC, Expr *pWhere){
+  int i;
+  WhereTerm *pTerm;
+  for(i=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
+    if( sqlite3ExprImpliesExpr(pTerm->pExpr, pWhere, iTab) ) return 1;
+  }
+  return 0;
+}
 
 /*
 ** Add all WhereLoop objects for a single table of the join where the table
@@ -4526,11 +4537,13 @@ static int whereLoopAddBtree(
   int b;                      /* A boolean value */
   WhereCost rSize;            /* number of rows in the table */
   WhereCost rLogSize;         /* Logarithm of the number of rows in the table */
+  WhereClause *pWC;           /* The parsed WHERE clause */
   
   pNew = pBuilder->pNew;
   pWInfo = pBuilder->pWInfo;
   pTabList = pWInfo->pTabList;
   pSrc = pTabList->a + pNew->iTab;
+  pWC = pBuilder->pWC;
   assert( !IsVirtual(pSrc->pTab) );
 
   if( pSrc->pIndex ){
@@ -4570,7 +4583,6 @@ static int whereLoopAddBtree(
    && !pSrc->isCorrelated
   ){
     /* Generate auto-index WhereLoops */
-    WhereClause *pWC = pBuilder->pWC;
     WhereTerm *pTerm;
     WhereTerm *pWCEnd = pWC->a + pWC->nTerm;
     for(pTerm=pWC->a; rc==SQLITE_OK && pTerm<pWCEnd; pTerm++){
@@ -4600,6 +4612,10 @@ static int whereLoopAddBtree(
   /* Loop over all indices
   */
   for(; rc==SQLITE_OK && pProbe; pProbe=pProbe->pNext, iSortIdx++){
+    if( pProbe->pPartIdxWhere!=0
+     && !whereUsablePartialIndex(pNew->iTab, pWC, pProbe->pPartIdxWhere) ){
+      continue;  /* Partial index inappropriate for this query */
+    }
     pNew->u.btree.nEq = 0;
     pNew->nLTerm = 0;
     pNew->iSortIdx = 0;