Avoid storing redundant fields in sorter records when the sort-key and data have

fields in common (as in "SELECT a FROM t1 ORDER BY 1").

FossilOrigin-Name: 0af62fdbd8e2aab14718ff8bcb5934f05463c176

3 files changed, 41 insertions, 11 deletions

diff --git a/src/expr.c b/src/expr.c
index c2b9c8fe4..165bb30f7 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -4086,8 +4086,13 @@ int sqlite3ExprCodeExprList(
   if( !ConstFactorOk(pParse) ) flags &= ~SQLITE_ECEL_FACTOR;
   for(pItem=pList->a, i=0; i<n; i++, pItem++){
     Expr *pExpr = pItem->pExpr;
-    if( (flags & SQLITE_ECEL_REF)!=0 && (j = pList->a[i].u.x.iOrderByCol)>0 ){
-      sqlite3VdbeAddOp2(v, copyOp, j+srcReg-1, target+i);
+    if( (flags & SQLITE_ECEL_REF)!=0 && (j = pItem->u.x.iOrderByCol)>0 ){
+      if( flags & SQLITE_ECEL_OMITREF ){
+        i--;
+        n--;
+      }else{
+        sqlite3VdbeAddOp2(v, copyOp, j+srcReg-1, target+i);
+      }
     }else if( (flags & SQLITE_ECEL_FACTOR)!=0 && sqlite3ExprIsConstant(pExpr) ){
       sqlite3ExprCodeAtInit(pParse, pExpr, target+i, 0);
     }else{
diff --git a/src/select.c b/src/select.c
index 199e13f11..003d42e72 100644
--- a/src/select.c
+++ b/src/select.c
@@ -533,11 +533,11 @@ static void pushOntoSorter(
   iLimit = pSelect->iOffset ? pSelect->iOffset+1 : pSelect->iLimit;
   pSort->labelDone = sqlite3VdbeMakeLabel(v);
   sqlite3ExprCodeExprList(pParse, pSort->pOrderBy, regBase, regOrigData,
-                          SQLITE_ECEL_DUP|SQLITE_ECEL_REF);
+                          SQLITE_ECEL_DUP);
   if( bSeq ){
     sqlite3VdbeAddOp2(v, OP_Sequence, pSort->iECursor, regBase+nExpr);
   }
-  if( nPrefixReg==0 ){
+  if( nPrefixReg==0 && nData>0 ){
     sqlite3ExprCodeMove(pParse, regData, regBase+nExpr+bSeq, nData);
   }
   sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase+nOBSat, nBase-nOBSat, regRecord);
@@ -666,7 +666,7 @@ static void codeDistinct(
 ** If srcTab is negative, then the pEList expressions
 ** are evaluated in order to get the data for this row.  If srcTab is
 ** zero or more, then data is pulled from srcTab and pEList is used only 
-** to get number columns and the datatype for each column.
+** to get the number of columns and the collation sequence for each column.
 */
 static void selectInnerLoop(
   Parse *pParse,          /* The parser context */
@@ -734,7 +734,25 @@ static void selectInnerLoop(
     }else{
       ecelFlags = 0;
     }
-    sqlite3ExprCodeExprList(pParse, pEList, regResult, 0, ecelFlags);
+    if( pSort && hasDistinct==0 && eDest!=SRT_EphemTab && eDest!=SRT_Table ){
+      /* For each expression in pEList that is a copy of an expression in
+      ** the ORDER BY clause (pSort->pOrderBy), set the associated 
+      ** iOrderByCol value to one more than the index of the ORDER BY 
+      ** expression within the sort-key that pushOntoSorter() will generate.
+      ** This allows the pEList field to be omitted from the sorted record,
+      ** saving space and CPU cycles.  */
+      ecelFlags |= (SQLITE_ECEL_OMITREF|SQLITE_ECEL_REF);
+      for(i=pSort->nOBSat; i<pSort->pOrderBy->nExpr; i++){
+        int j;
+        if( (j = pSort->pOrderBy->a[i].u.x.iOrderByCol)>0 ){
+          pEList->a[j-1].u.x.iOrderByCol = i+1-pSort->nOBSat;
+        }
+      }
+
+      assert( eDest==SRT_Set || eDest==SRT_Mem 
+           || eDest==SRT_Coroutine || eDest==SRT_Output );
+    }
+    nResultCol = sqlite3ExprCodeExprList(pParse,pEList,regResult,0,ecelFlags);
   }
 
   /* If the DISTINCT keyword was present on the SELECT statement
@@ -900,11 +918,12 @@ static void selectInnerLoop(
     ** memory cells and break out of the scan loop.
     */
     case SRT_Mem: {
-      assert( nResultCol==pDest->nSdst );
       if( pSort ){
+        assert( nResultCol<=pDest->nSdst );
         pushOntoSorter(
             pParse, pSort, p, regResult, regResult, nResultCol, nPrefixReg);
       }else{
+        assert( nResultCol==pDest->nSdst );
         assert( regResult==iParm );
         /* The LIMIT clause will jump out of the loop for us */
       }
@@ -1202,14 +1221,13 @@ static void generateSortTail(
   int iParm = pDest->iSDParm;
   int regRow;
   int regRowid;
+  int iCol;
   int nKey;
   int iSortTab;                   /* Sorter cursor to read from */
   int nSortData;                  /* Trailing values to read from sorter */
   int i;
   int bSeq;                       /* True if sorter record includes seq. no. */
-#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
   struct ExprList_item *aOutEx = p->pEList->a;
-#endif
 
   assert( addrBreak<0 );
   if( pSort->labelBkOut ){
@@ -1247,8 +1265,14 @@ static void generateSortTail(
     iSortTab = iTab;
     bSeq = 1;
   }
-  for(i=0; i<nSortData; i++){
-    sqlite3VdbeAddOp3(v, OP_Column, iSortTab, nKey+bSeq+i, regRow+i);
+  for(i=0, iCol=nKey+bSeq; i<nSortData; i++){
+    int iRead;
+    if( aOutEx[i].u.x.iOrderByCol ){
+      iRead = aOutEx[i].u.x.iOrderByCol-1;
+    }else{
+      iRead = iCol++;
+    }
+    sqlite3VdbeAddOp3(v, OP_Column, iSortTab, iRead, regRow+i);
     VdbeComment((v, "%s", aOutEx[i].zName ? aOutEx[i].zName : aOutEx[i].zSpan));
   }
   switch( eDest ){
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index c0e5aa01b..88662958d 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3706,6 +3706,7 @@ int sqlite3ExprCodeExprList(Parse*, ExprList*, int, int, u8);
 #define SQLITE_ECEL_DUP      0x01  /* Deep, not shallow copies */
 #define SQLITE_ECEL_FACTOR   0x02  /* Factor out constant terms */
 #define SQLITE_ECEL_REF      0x04  /* Use ExprList.u.x.iOrderByCol */
+#define SQLITE_ECEL_OMITREF  0x08  /* Omit if ExprList.u.x.iOrderByCol */
 void sqlite3ExprIfTrue(Parse*, Expr*, int, int);
 void sqlite3ExprIfFalse(Parse*, Expr*, int, int);
 void sqlite3ExprIfFalseDup(Parse*, Expr*, int, int);