Use the estimated number of rows computed for subqueries in the cost

computations for outer queries.

FossilOrigin-Name: 56bbc539246a6dc9f1ae1edb898db7a4f6f6d322

3 files changed, 24 insertions, 0 deletions

diff --git a/src/select.c b/src/select.c
index 0f83bbb36..5c5b61589 100644
--- a/src/select.c
+++ b/src/select.c
@@ -1433,6 +1433,8 @@ static void computeLimitRegisters(Parse *pParse, Select *p, int iBreak){
       VdbeComment((v, "LIMIT counter"));
       if( n==0 ){
         sqlite3VdbeAddOp2(v, OP_Goto, 0, iBreak);
+      }else{
+        if( p->nSelectRow > (double)n ) p->nSelectRow = (double)n;
       }
     }else{
       sqlite3ExprCode(pParse, p->pLimit, iLimit);
@@ -1594,6 +1596,7 @@ static int multiSelect(
   switch( p->op ){
     case TK_ALL: {
       int addr = 0;
+      int nLimit;
       assert( !pPrior->pLimit );
       pPrior->pLimit = p->pLimit;
       pPrior->pOffset = p->pOffset;
@@ -1616,6 +1619,13 @@ static int multiSelect(
       testcase( rc!=SQLITE_OK );
       pDelete = p->pPrior;
       p->pPrior = pPrior;
+      p->nSelectRow += pPrior->nSelectRow;
+      if( pPrior->pLimit
+       && sqlite3ExprIsInteger(pPrior->pLimit, &nLimit)
+       && p->nSelectRow > (double)nLimit 
+      ){
+        p->nSelectRow = (double)nLimit;
+      }
       if( addr ){
         sqlite3VdbeJumpHere(v, addr);
       }
@@ -1688,6 +1698,7 @@ static int multiSelect(
       pDelete = p->pPrior;
       p->pPrior = pPrior;
       p->pOrderBy = 0;
+      if( p->op==TK_UNION ) p->nSelectRow += pPrior->nSelectRow;
       sqlite3ExprDelete(db, p->pLimit);
       p->pLimit = pLimit;
       p->pOffset = pOffset;
@@ -1767,6 +1778,7 @@ static int multiSelect(
       testcase( rc!=SQLITE_OK );
       pDelete = p->pPrior;
       p->pPrior = pPrior;
+      if( p->nSelectRow>pPrior->nSelectRow ) p->nSelectRow = pPrior->nSelectRow;
       sqlite3ExprDelete(db, p->pLimit);
       p->pLimit = pLimit;
       p->pOffset = pOffset;
@@ -2353,6 +2365,7 @@ static int multiSelectOrderBy(
     sqlite3VdbeAddOp2(v, OP_Gosub, regOutB, addrOutB);
     sqlite3VdbeAddOp1(v, OP_Yield, regAddrB);
     sqlite3VdbeAddOp2(v, OP_Goto, 0, addrEofA);
+    p->nSelectRow += pPrior->nSelectRow;
   }
 
   /* Generate a subroutine to run when the results from select B
@@ -2360,6 +2373,7 @@ static int multiSelectOrderBy(
   */
   if( op==TK_INTERSECT ){
     addrEofB = addrEofA;
+    if( p->nSelectRow > pPrior->nSelectRow ) p->nSelectRow = pPrior->nSelectRow;
   }else{  
     VdbeNoopComment((v, "eof-B subroutine"));
     addrEofB = sqlite3VdbeAddOp2(v, OP_If, regEofA, labelEnd);
@@ -3754,6 +3768,7 @@ int sqlite3Select(
       explainSetInteger(pItem->iSelectId, pParse->iNextSelectId);
       sqlite3Select(pParse, pSub, &dest);
       pItem->isPopulated = 1;
+      pItem->pTab->nRowEst = (unsigned)pSub->nSelectRow;
     }
     if( /*pParse->nErr ||*/ db->mallocFailed ){
       goto select_end;
@@ -3846,6 +3861,7 @@ int sqlite3Select(
   /* Set the limiter.
   */
   iEnd = sqlite3VdbeMakeLabel(v);
+  p->nSelectRow = (double)LARGEST_INT64;
   computeLimitRegisters(pParse, p, iEnd);
 
   /* Open a virtual index to use for the distinct set.
@@ -3869,6 +3885,7 @@ int sqlite3Select(
     */
     pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, &pOrderBy, 0);
     if( pWInfo==0 ) goto select_end;
+    if( pWInfo->nRowOut < p->nSelectRow ) p->nSelectRow = pWInfo->nRowOut;
 
     /* If sorting index that was created by a prior OP_OpenEphemeral 
     ** instruction ended up not being needed, then change the OP_OpenEphemeral
@@ -3913,6 +3930,9 @@ int sqlite3Select(
       for(k=pGroupBy->nExpr, pItem=pGroupBy->a; k>0; k--, pItem++){
         pItem->iAlias = 0;
       }
+      if( p->nSelectRow>(double)100 ) p->nSelectRow = (double)100;
+    }else{
+      p->nSelectRow = (double)1;
     }
 
  
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index b9eb650d8..c02a0e448 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -1947,6 +1947,7 @@ struct WhereInfo {
   int nLevel;                    /* Number of nested loop */
   struct WhereClause *pWC;       /* Decomposition of the WHERE clause */
   double savedNQueryLoop;        /* pParse->nQueryLoop outside the WHERE loop */
+  double nRowOut;                /* Estimated number of output rows */
   WhereLevel a[1];               /* Information about each nest loop in WHERE */
 };
 
@@ -2022,6 +2023,7 @@ struct Select {
   Expr *pOffset;         /* OFFSET expression. NULL means not used. */
   int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */
   int addrOpenEphm[3];   /* OP_OpenEphem opcodes related to this select */
+  double nSelectRow;     /* Estimated number of result rows */
 };
 
 /*
diff --git a/src/where.c b/src/where.c
index 1d6641ee8..751c7a99c 100644
--- a/src/where.c
+++ b/src/where.c
@@ -4423,6 +4423,7 @@ WhereInfo *sqlite3WhereBegin(
   */
   sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
   notReady = ~(Bitmask)0;
+  pWInfo->nRowOut = (double)1;
   for(i=0, pLevel=pWInfo->a; i<nTabList; i++, pLevel++){
     Table *pTab;     /* Table to open */
     int iDb;         /* Index of database containing table/index */
@@ -4430,6 +4431,7 @@ WhereInfo *sqlite3WhereBegin(
     pTabItem = &pTabList->a[pLevel->iFrom];
     pTab = pTabItem->pTab;
     pLevel->iTabCur = pTabItem->iCursor;
+    pWInfo->nRowOut *= pLevel->plan.nRow;
     iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
     if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
       /* Do nothing */