Omit all use of Expr nodes for TK_AS, as those nodes no longer served a useful

purpose and in fact interferred with the query planner.

FossilOrigin-Name: 7ab0b258eabfcfb7f1b0bd1b12e166d2f267823d

1 files changed, 3 insertions, 35 deletions

diff --git a/src/resolve.c b/src/resolve.c
index 22df22394..2c4212ba7 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -45,30 +45,6 @@ static void incrAggFunctionDepth(Expr *pExpr, int N){
 ** Turn the pExpr expression into an alias for the iCol-th column of the
 ** result set in pEList.
 **
-** If the result set column is a simple column reference, then this routine
-** makes an exact copy.  But for any other kind of expression, this
-** routine make a copy of the result set column as the argument to the
-** TK_AS operator.  The TK_AS operator causes the expression to be
-** evaluated just once and then reused for each alias.
-**
-** The reason for suppressing the TK_AS term when the expression is a simple
-** column reference is so that the column reference will be recognized as
-** usable by indices within the WHERE clause processing logic. 
-**
-** The TK_AS operator is inhibited if zType[0]=='G'.  This means
-** that in a GROUP BY clause, the expression is evaluated twice.  Hence:
-**
-**     SELECT random()%5 AS x, count(*) FROM tab GROUP BY x
-**
-** Is equivalent to:
-**
-**     SELECT random()%5 AS x, count(*) FROM tab GROUP BY random()%5
-**
-** The result of random()%5 in the GROUP BY clause is probably different
-** from the result in the result-set.  On the other hand Standard SQL does
-** not allow the GROUP BY clause to contain references to result-set columns.
-** So this should never come up in well-formed queries.
-**
 ** If the reference is followed by a COLLATE operator, then make sure
 ** the COLLATE operator is preserved.  For example:
 **
@@ -102,19 +78,11 @@ static void resolveAlias(
   db = pParse->db;
   pDup = sqlite3ExprDup(db, pOrig, 0);
   if( pDup==0 ) return;
-  if( pOrig->op!=TK_COLUMN && zType[0]!='G' ){
-    incrAggFunctionDepth(pDup, nSubquery);
-    pDup = sqlite3PExpr(pParse, TK_AS, pDup, 0, 0);
-    if( pDup==0 ) return;
-    ExprSetProperty(pDup, EP_Skip);
-    if( pEList->a[iCol].u.x.iAlias==0 ){
-      pEList->a[iCol].u.x.iAlias = (u16)(++pParse->nAlias);
-    }
-    pDup->iTable = pEList->a[iCol].u.x.iAlias;
-  }
+  if( zType[0]!='G' ) incrAggFunctionDepth(pDup, nSubquery);
   if( pExpr->op==TK_COLLATE ){
     pDup = sqlite3ExprAddCollateString(pParse, pDup, pExpr->u.zToken);
   }
+  ExprSetProperty(pDup, EP_Alias);
 
   /* Before calling sqlite3ExprDelete(), set the EP_Static flag. This 
   ** prevents ExprDelete() from deleting the Expr structure itself,
@@ -506,7 +474,7 @@ static int lookupName(
 lookupname_end:
   if( cnt==1 ){
     assert( pNC!=0 );
-    if( pExpr->op!=TK_AS ){
+    if( !ExprHasProperty(pExpr, EP_Alias) ){
       sqlite3AuthRead(pParse, pExpr, pSchema, pNC->pSrcList);
     }
     /* Increment the nRef value on all name contexts from TopNC up to