Reduce the size of the WhereScan object by 24 bytes while also clarifying its

operation.

FossilOrigin-Name: cbc3c9a8bf169ae0b21f26855038502c6cc25cfe

manifest

@@ -1,5 +1,5 @@
-C Evaluate\sexpressions\sonly\sonce\swhen\sthe\ssame\sexpression\sis\sused\sin\sboth\sthe\nresult\sset\sand\sin\sthe\sORDER\sBY\sclause.
+C Reduce\sthe\ssize\sof\sthe\sWhereScan\sobject\sby\s24\sbytes\swhile\salso\sclarifying\sits\noperation.
-D 2015-08-26T14:01:41.658
+D 2015-08-26T21:08:04.505
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in e2218eb228374422969de7b1680eda6864affcef
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -414,8 +414,8 @@ F src/vxworks.h c18586c8edc1bddbc15c004fa16aeb1e1342b4fb
 F src/wal.c 6fb6b68969e4692593c2552c4e7bff5882de2cb8
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c 2e14d17f592d176b6dc879c33fbdec4fbccaa2ba
-F src/where.c fb8546b8053433bfb39f6c39fdc99c111a6f97c5
+F src/where.c caabc9ec1e86168d7717833700cfed01a75f687a
-F src/whereInt.h 880a8599226ac1c00203490d934f3ed79b292572
+F src/whereInt.h 901c17c1e3c82745ad9b85b4471543fa59c980e9
 F src/wherecode.c 3d9113cc307ffeed58db41fe9f2d807c94787ab5
 F src/whereexpr.c 1a308d1ee5144890d21ea9cf70d49bc96a83432b
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
@@ -1380,7 +1380,7 @@ F tool/vdbe_profile.tcl 67746953071a9f8f2f668b73fe899074e2c6d8c1
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 58ba73630ecc4bc58b03a7962dd45b305ef605ef
+P c2f3bbad778504681b39ab9399a1eb3c1a35ab3f
-R 657299463d01da646731fb6b8ab7d9fe
+R f5f6b9b31662d17ccccce315f9a81df1
 U drh
-Z 83e3936f8767c9500521d2082aa870a1
+Z be2744e78cce20e5ac9fa855b3738fc2

manifest.uuid

@@ -1 +1 @@
-c2f3bbad778504681b39ab9399a1eb3c1a35ab3f
+cbc3c9a8bf169ae0b21f26855038502c6cc25cfe

src/where.c

@@ -171,37 +171,37 @@ static void createMask(WhereMaskSet *pMaskSet, int iCursor){
 */
 static WhereTerm *whereScanNext(WhereScan *pScan){
   int iCur;            /* The cursor on the LHS of the term */
-  int iColumn;         /* The column on the LHS of the term.  -1 for IPK */
+  i16 iColumn;         /* The column on the LHS of the term.  -1 for IPK */
   Expr *pX;            /* An expression being tested */
   WhereClause *pWC;    /* Shorthand for pScan->pWC */
   WhereTerm *pTerm;    /* The term being tested */
   int k = pScan->k;    /* Where to start scanning */
 
   while( pScan->iEquiv<=pScan->nEquiv ){
-    iCur = pScan->aEquiv[pScan->iEquiv-2];
+    iCur = pScan->aiCur[pScan->iEquiv-1];
-    iColumn = pScan->aEquiv[pScan->iEquiv-1];
+    iColumn = pScan->aiColumn[pScan->iEquiv-1];
     while( (pWC = pScan->pWC)!=0 ){
       for(pTerm=pWC->a+k; k<pWC->nTerm; k++, pTerm++){
         if( pTerm->leftCursor==iCur
          && pTerm->u.leftColumn==iColumn
-         && (pScan->iEquiv<=2 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
+         && (pScan->iEquiv<=1 || !ExprHasProperty(pTerm->pExpr, EP_FromJoin))
         ){
           if( (pTerm->eOperator & WO_EQUIV)!=0
-           && pScan->nEquiv<ArraySize(pScan->aEquiv)
+           && pScan->nEquiv<ArraySize(pScan->aiCur)
           ){
             int j;
             pX = sqlite3ExprSkipCollate(pTerm->pExpr->pRight);
             assert( pX->op==TK_COLUMN );
-            for(j=0; j<pScan->nEquiv; j+=2){
+            for(j=0; j<pScan->nEquiv; j++){
-              if( pScan->aEquiv[j]==pX->iTable
+              if( pScan->aiCur[j]==pX->iTable
-               && pScan->aEquiv[j+1]==pX->iColumn ){
+               && pScan->aiColumn[j]==pX->iColumn ){
                   break;
               }
             }
             if( j==pScan->nEquiv ){
-              pScan->aEquiv[j] = pX->iTable;
+              pScan->aiCur[j] = pX->iTable;
-              pScan->aEquiv[j+1] = pX->iColumn;
+              pScan->aiColumn[j] = pX->iColumn;
-              pScan->nEquiv += 2;
+              pScan->nEquiv++;
             }
           }
           if( (pTerm->eOperator & pScan->opMask)!=0 ){
@@ -223,8 +223,8 @@ static WhereTerm *whereScanNext(WhereScan *pScan){
             }
             if( (pTerm->eOperator & (WO_EQ|WO_IS))!=0
              && (pX = pTerm->pExpr->pRight)->op==TK_COLUMN
-             && pX->iTable==pScan->aEquiv[0]
+             && pX->iTable==pScan->aiCur[0]
-             && pX->iColumn==pScan->aEquiv[1]
+             && pX->iColumn==pScan->aiColumn[0]
             ){
               testcase( pTerm->eOperator & WO_IS );
               continue;
@@ -239,7 +239,7 @@ static WhereTerm *whereScanNext(WhereScan *pScan){
     }
     pScan->pWC = pScan->pOrigWC;
     k = 0;
-    pScan->iEquiv += 2;
+    pScan->iEquiv++;
   }
   return 0;
 }
@@ -285,10 +285,10 @@ static WhereTerm *whereScanInit(
   }
   pScan->opMask = opMask;
   pScan->k = 0;
-  pScan->aEquiv[0] = iCur;
+  pScan->aiCur[0] = iCur;
-  pScan->aEquiv[1] = iColumn;
+  pScan->aiColumn[0] = iColumn;
-  pScan->nEquiv = 2;
+  pScan->nEquiv = 1;
-  pScan->iEquiv = 2;
+  pScan->iEquiv = 1;
   return whereScanNext(pScan);
 }
 
@@ -301,12 +301,10 @@ static WhereTerm *whereScanInit(
 ** The term returned might by Y=<expr> if there is another constraint in
 ** the WHERE clause that specifies that X=Y.  Any such constraints will be
 ** identified by the WO_EQUIV bit in the pTerm->eOperator field.  The
-** aEquiv[] array holds X and all its equivalents, with each SQL variable
+** aiCur[]/iaColumn[] arrays hold X and all its equivalents. There are 11
-** taking up two slots in aEquiv[].  The first slot is for the cursor number
+** slots in aiCur[]/aiColumn[] so that means we can look for X plus up to 10
-** and the second is for the column number.  There are 22 slots in aEquiv[]
+** other equivalent values.  Hence a search for X will return <expr> if X=A1
-** so that means we can look for X plus up to 10 other equivalent values.
+** and A1=A2 and A2=A3 and ... and A9=A10 and A10=<expr>.
-** Hence a search for X will return <expr> if X=A1 and A1=A2 and A2=A3
-** and ... and A9=A10 and A10=<expr>.
 **
 ** If there are multiple terms in the WHERE clause of the form "X <op> <expr>"
 ** then try for the one with no dependencies on <expr> - in other words where

src/whereInt.h

@@ -291,7 +291,8 @@ struct WhereScan {
   unsigned char iEquiv;      /* Next unused slot in aEquiv[] */
   u32 opMask;                /* Acceptable operators */
   int k;                     /* Resume scanning at this->pWC->a[this->k] */
-  int aEquiv[22];            /* Cursor,Column pairs for equivalence classes */
+  int aiCur[11];             /* Cursors in the equivalence class */
+  i16 aiColumn[11];          /* Corresponding column number in the eq-class */
 };
 
 /*