Do a better job of detecting when a WHERE clause term might be useful to

an expression index.  Fix for performance regression reported by
[forum:/forumpost/e65800d8cb|forum thread e65800d8cb].

FossilOrigin-Name: 44200596aa943963bc6ca98b5d4fd5b9235d1109d8dfc1a75eeae353b4239142

manifest

@@ -1,5 +1,5 @@
-C Fix\sa\sproblem\swith\sthe\sfts5\strigram\stokenizer\sand\sLIKE\sor\sGLOB\spatterns\sfor\swhich\scontain\sruns\sof\s2\sor\sfewer\snon-wildcard\scharacters\sthat\sare\s3\sor\smore\sbytes\swhen\sencoded\sas\sutf-8.
-D 2023-02-10T17:17:04.066
+C Do\sa\sbetter\sjob\sof\sdetecting\swhen\sa\sWHERE\sclause\sterm\smight\sbe\suseful\sto\nan\sexpression\sindex.\s\sFix\sfor\sperformance\sregression\sreported\sby\n[forum:/forumpost/e65800d8cb|forum\sthread\se65800d8cb].
+D 2023-02-10T21:53:33.465
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -709,7 +709,7 @@ F src/walker.c f890a3298418d7cba3b69b8803594fdc484ea241206a8dfa99db6dd36f8cbb3b
 F src/where.c 5b20d08699c9a55c0556661ff6f937dd1c8e27567b7553e48d477d3fad22ec4c
 F src/whereInt.h e25203e5bfee149f5f1225ae0166cfb4f1e65490c998a024249e98bb0647377c
 F src/wherecode.c 76bca3379219880d2527493b71a3be49e696f75396d3481e4de5d4ceec7886b2
-F src/whereexpr.c 7c5671a04b00c876bec5e99fd4e6f688065feb4773160fbf76fd7900d2901777
+F src/whereexpr.c aa9467272033315424c76f446ca0b65683d6002ededaa65b6a6d4c00b3b525b8
 F src/window.c 76a27cff9ea2ded0c2c3527187029259440fabcc4cc4c07b11d942c78494a614
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/affinity2.test ce1aafc86e110685b324e9a763eab4f2a73f737842ec3b687bd965867de90627
@@ -1884,7 +1884,7 @@ F test/whereH.test e4b07f7a3c2f5d31195cd33710054c78667573b2
 F test/whereI.test c4bb7e2ca56d49bd8ab5c7bd085b8b83e353922b46904d68aefb3c7468643581
 F test/whereJ.test fc05e374cc9f2dc204148d6c06822c380ad388895fe97a6d335b94a26a08aecf
 F test/whereK.test 0270ab7f04ba5436fb9156d31d642a1c82727f4c4bfe5ba90d435c78cf44684a
-F test/whereL.test 50171e3ec00b4c8ad5ec773119a35d9e9642cec45154b44c366d628326479f4d
+F test/whereL.test 9d7c8a9f4e5e82d6859e61cf8758c3856c7e0a7fd8be11c92cac8c3ec39228fd
 F test/whereM.test 0dbc9998783458ddcf3cc078ca7c2951d8b2677d472ecf0028f449ed327c0250
 F test/wherefault.test 6cf2a9c5712952d463d3f45ebee7f6caf400984df51a195d884cfb7eb0e837a7
 F test/wherelfault.test 9012e4ef5259058b771606616bd007af5d154e64cc25fa9fd4170f6411db44e3
@@ -2045,8 +2045,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 734766451123c98a467c3407562eaa097b3307c8a275e1c8dd93e4654fe78014
-R 5bf915f087ec1f7e7765a72585c21ed1
-U dan
-Z 46cdaf9bdec2b8801443f3e6fa3042be
+P 00714b39b39c51519edbc0194f98c7275fecf96763a06fd95db6e1d81bb9f1f1
+R 122a35632c84f1a86bc1efeb49e3bb37
+U drh
+Z 7d2b0fd613ff6bddf59b196d4f5df2a1
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-00714b39b39c51519edbc0194f98c7275fecf96763a06fd95db6e1d81bb9f1f1
+44200596aa943963bc6ca98b5d4fd5b9235d1109d8dfc1a75eeae353b4239142

src/whereexpr.c

@@ -974,36 +974,38 @@ static Bitmask exprSelectUsage(WhereMaskSet *pMaskSet, Select *pS){
 */
 static SQLITE_NOINLINE int exprMightBeIndexed2(
   SrcList *pFrom,        /* The FROM clause */
-  Bitmask mPrereq,       /* Bitmask of FROM clause terms referenced by pExpr */
   int *aiCurCol,         /* Write the referenced table cursor and column here */
-  Expr *pExpr            /* An operand of a comparison operator */
+  Expr *pExpr,           /* An operand of a comparison operator */
+  int j                  /* Start looking with the j-th pFrom entry */
 ){
   Index *pIdx;
   int i;
   int iCur;
-  for(i=0; mPrereq>1; i++, mPrereq>>=1){}
-  iCur = pFrom->a[i].iCursor;
-  for(pIdx=pFrom->a[i].pTab->pIndex; pIdx; pIdx=pIdx->pNext){
-    if( pIdx->aColExpr==0 ) continue;
-    for(i=0; i<pIdx->nKeyCol; i++){
-      if( pIdx->aiColumn[i]!=XN_EXPR ) continue;
-      assert( pIdx->bHasExpr );
-      if( sqlite3ExprCompareSkip(pExpr, pIdx->aColExpr->a[i].pExpr, iCur)==0 ){
-        aiCurCol[0] = iCur;
-        aiCurCol[1] = XN_EXPR;
-        return 1;
+  do{
+    iCur = pFrom->a[j].iCursor;
+    for(pIdx=pFrom->a[j].pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      if( pIdx->aColExpr==0 ) continue;
+      for(i=0; i<pIdx->nKeyCol; i++){
+        if( pIdx->aiColumn[i]!=XN_EXPR ) continue;
+        assert( pIdx->bHasExpr );
+        if( sqlite3ExprCompareSkip(pExpr,pIdx->aColExpr->a[i].pExpr,iCur)==0 ){
+          aiCurCol[0] = iCur;
+          aiCurCol[1] = XN_EXPR;
+          return 1;
+        }
       }
     }
-  }
+  }while( ++j < pFrom->nSrc );
   return 0;
 }
 static int exprMightBeIndexed(
   SrcList *pFrom,        /* The FROM clause */
-  Bitmask mPrereq,       /* Bitmask of FROM clause terms referenced by pExpr */
   int *aiCurCol,         /* Write the referenced table cursor & column here */
   Expr *pExpr,           /* An operand of a comparison operator */
   int op                 /* The specific comparison operator */
 ){
+  int i;
+
   /* If this expression is a vector to the left or right of a 
   ** inequality constraint (>, <, >= or <=), perform the processing 
   ** on the first element of the vector.  */
@@ -1013,7 +1015,6 @@ static int exprMightBeIndexed(
   if( pExpr->op==TK_VECTOR && (op>=TK_GT && ALWAYS(op<=TK_GE)) ){
     assert( ExprUseXList(pExpr) );
     pExpr = pExpr->x.pList->a[0].pExpr;
-
   }
 
   if( pExpr->op==TK_COLUMN ){
@@ -1021,9 +1022,16 @@ static int exprMightBeIndexed(
     aiCurCol[1] = pExpr->iColumn;
     return 1;
   }
-  if( mPrereq==0 ) return 0;                 /* No table references */
-  if( (mPrereq&(mPrereq-1))!=0 ) return 0;   /* Refs more than one table */
-  return exprMightBeIndexed2(pFrom,mPrereq,aiCurCol,pExpr);
+
+  for(i=0; i<pFrom->nSrc; i++){
+    Index *pIdx;
+    for(pIdx=pFrom->a[i].pTab->pIndex; pIdx; pIdx=pIdx->pNext){
+      if( pIdx->aColExpr ){
+        return exprMightBeIndexed2(pFrom,aiCurCol,pExpr,i);
+      }
+    }
+  }
+  return 0;
 }
 
 
@@ -1149,7 +1157,7 @@ static void exprAnalyze(
       pLeft = pLeft->x.pList->a[pTerm->u.x.iField-1].pExpr;
     }
 
-    if( exprMightBeIndexed(pSrc, prereqLeft, aiCurCol, pLeft, op) ){
+    if( exprMightBeIndexed(pSrc, aiCurCol, pLeft, op) ){
       pTerm->leftCursor = aiCurCol[0];
       assert( (pTerm->eOperator & (WO_OR|WO_AND))==0 );
       pTerm->u.x.leftColumn = aiCurCol[1];
@@ -1157,7 +1165,7 @@ static void exprAnalyze(
     }
     if( op==TK_IS ) pTerm->wtFlags |= TERM_IS;
     if( pRight 
-     && exprMightBeIndexed(pSrc, pTerm->prereqRight, aiCurCol, pRight, op)
+     && exprMightBeIndexed(pSrc, aiCurCol, pRight, op)
      && !ExprHasProperty(pRight, EP_FixedCol)
     ){
       WhereTerm *pNew;

test/whereL.test

@@ -189,5 +189,24 @@ do_execsql_test 610 {
     AND A.RunYearMonth = B.RunYearMonth;
 } {4 202004 4 202004 5 202004 5 202004}
 
+# 2023-02-10 https://sqlite.org/forum/forumpost/0a539c76db3b9e29
+# The original constant propagation implementation caused a performance
+# regression.  Because "abs(v)" was rewritten into "abs(1)" it no longer
+# matches the indexed column and the index is not used.
+# 
+reset_db
+do_execsql_test 700 {
+  CREATE TABLE t1(v INTEGER);
+  WITH RECURSIVE c(x) AS (VALUES(-10) UNION ALL SELECT x+1 FROM c WHERE x<10)
+    INSERT INTO t1(v) SELECT x FROM c;
+  CREATE INDEX idx ON t1( abs(v) );
+  SELECT v FROM t1 WHERE abs(v)=1 and v=1;
+} 1
+do_eqp_test 710 {
+  SELECT v FROM t1 WHERE abs(v)=1 and v=1;
+} {
+  QUERY PLAN
+  `--SEARCH t1 USING INDEX idx (<expr>=?)
+}
 
 finish_test