Attempt to factor out constant functions from the interior of table scans,

since functions can often be expensive to compute.

FossilOrigin-Name: 62e9270a8057d758621da33adb27fad14225f95d

1 files changed, 26 insertions, 13 deletions

diff --git a/src/expr.c b/src/expr.c
index 3bb0ca03f..2fb5dff8c 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -3612,6 +3612,9 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
       u8 enc = ENC(db);      /* The text encoding used by this database */
       CollSeq *pColl = 0;    /* A collating sequence */
 
+      if( ConstFactorOk(pParse) && sqlite3ExprIsConstantNotJoin(pExpr) ){
+        return sqlite3ExprCodeAtInit(pParse, pExpr, -1, 1);
+      }
       assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
       if( ExprHasProperty(pExpr, EP_TokenOnly) ){
         pFarg = 0;
@@ -3992,8 +3995,16 @@ int sqlite3ExprCodeTarget(Parse *pParse, Expr *pExpr, int target){
 
 /*
 ** Factor out the code of the given expression to initialization time.
+**
+** If regDest>=0 then the result is always stored in that register.
+** If regDest<0 then this routine is free to store the value whereever
+** it wants.  The register where the expression is stored is returned.
+**
+** If regDest<0 and an equivalent expression already exists elsewhere
+** in the initialization expressions, then routine just returns the
+** register of the prior occurrance.
 */
-void sqlite3ExprCodeAtInit(
+int sqlite3ExprCodeAtInit(
   Parse *pParse,    /* Parsing context */
   Expr *pExpr,      /* The expression to code when the VDBE initializes */
   int regDest,      /* Store the value in this register */
@@ -4002,6 +4013,18 @@ void sqlite3ExprCodeAtInit(
   ExprList *p;
   assert( ConstFactorOk(pParse) );
   p = pParse->pConstExpr;
+  if( regDest<0 ){
+    if( p && reusable ){
+      struct ExprList_item *pItem;
+      int i;
+      for(pItem=p->a, i=p->nExpr; i>0; pItem++, i--){
+        if( pItem->reusable && sqlite3ExprCompare(pItem->pExpr,pExpr,-1)==0 ){
+          return pItem->u.iConstExprReg;
+        }
+      }
+    }
+    regDest = ++pParse->nMem;
+  }
   pExpr = sqlite3ExprDup(pParse->db, pExpr, 0);
   p = sqlite3ExprListAppend(pParse, p, pExpr);
   if( p ){
@@ -4010,6 +4033,7 @@ void sqlite3ExprCodeAtInit(
      pItem->reusable = reusable;
   }
   pParse->pConstExpr = p;
+  return regDest;
 }
 
 /*
@@ -4032,19 +4056,8 @@ int sqlite3ExprCodeTemp(Parse *pParse, Expr *pExpr, int *pReg){
    && pExpr->op!=TK_REGISTER
    && sqlite3ExprIsConstantNotJoin(pExpr)
   ){
-    ExprList *p = pParse->pConstExpr;
-    int i;
     *pReg  = 0;
-    if( p ){
-      struct ExprList_item *pItem;
-      for(pItem=p->a, i=p->nExpr; i>0; pItem++, i--){
-        if( pItem->reusable && sqlite3ExprCompare(pItem->pExpr,pExpr,-1)==0 ){
-          return pItem->u.iConstExprReg;
-        }
-      }
-    }
-    r2 = ++pParse->nMem;
-    sqlite3ExprCodeAtInit(pParse, pExpr, r2, 1);
+    r2 = sqlite3ExprCodeAtInit(pParse, pExpr, -1, 1);
   }else{
     int r1 = sqlite3GetTempReg(pParse);
     r2 = sqlite3ExprCodeTarget(pParse, pExpr, r1);