In the parse tree, combine LIMIT and OFFSET into a single expression rooted

on a TK_LIMIT node, for a small code size reduction and performance increase,
and a reduction in code complexity.

FossilOrigin-Name: 3925facd942c9df663f9b29b1e6f94f6be14af8c2b99eb691bfc836b4c220826

1 files changed, 8 insertions, 6 deletions

diff --git a/src/expr.c b/src/expr.c
index 0a5dc913f..5027f994d 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -663,7 +663,6 @@ static void heightOfSelect(Select *p, int *pnHeight){
     heightOfExpr(p->pWhere, pnHeight);
     heightOfExpr(p->pHaving, pnHeight);
     heightOfExpr(p->pLimit, pnHeight);
-    heightOfExpr(p->pOffset, pnHeight);
     heightOfExprList(p->pEList, pnHeight);
     heightOfExprList(p->pGroupBy, pnHeight);
     heightOfExprList(p->pOrderBy, pnHeight);
@@ -1462,7 +1461,6 @@ Select *sqlite3SelectDup(sqlite3 *db, Select *pDup, int flags){
     pNew->pNext = pNext;
     pNew->pPrior = 0;
     pNew->pLimit = sqlite3ExprDup(db, p->pLimit, flags);
-    pNew->pOffset = sqlite3ExprDup(db, p->pOffset, flags);
     pNew->iLimit = 0;
     pNew->iOffset = 0;
     pNew->selFlags = p->selFlags & ~SF_UsesEphemeral;
@@ -2099,7 +2097,6 @@ static Select *isCandidateForInOpt(Expr *pX){
   }
   assert( p->pGroupBy==0 );              /* Has no GROUP BY clause */
   if( p->pLimit ) return 0;              /* Has no LIMIT clause */
-  assert( p->pOffset==0 );               /* No LIMIT means no OFFSET */
   if( p->pWhere ) return 0;              /* Has no WHERE clause */
   pSrc = p->pSrc;
   assert( pSrc!=0 );
@@ -2739,6 +2736,7 @@ int sqlite3CodeSubselect(
       Select *pSel;                         /* SELECT statement to encode */
       SelectDest dest;                      /* How to deal with SELECT result */
       int nReg;                             /* Registers to allocate */
+      Expr *pLimit;                         /* New limit expression */
 
       testcase( pExpr->op==TK_EXISTS );
       testcase( pExpr->op==TK_SELECT );
@@ -2760,9 +2758,13 @@ int sqlite3CodeSubselect(
         sqlite3VdbeAddOp2(v, OP_Integer, 0, dest.iSDParm);
         VdbeComment((v, "Init EXISTS result"));
       }
-      sqlite3ExprDelete(pParse->db, pSel->pLimit);
-      pSel->pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,
-                                  &sqlite3IntTokens[1], 0);
+      pLimit = sqlite3ExprAlloc(pParse->db, TK_INTEGER,&sqlite3IntTokens[1], 0);
+      if( pSel->pLimit ){
+        sqlite3ExprDelete(pParse->db, pSel->pLimit->pLeft);
+        pSel->pLimit->pLeft = pLimit;
+      }else{
+        pSel->pLimit = sqlite3PExpr(pParse, TK_LIMIT, pLimit, 0);
+      }
       pSel->iLimit = 0;
       pSel->selFlags &= ~SF_MultiValue;
       if( sqlite3Select(pParse, pSel, &dest) ){