Optimizations to the Walker object and its methods to make the code a little

smaller and to help it run a little faster.

FossilOrigin-Name: 6854a34ed708259f2280f7ee56cec09f7fc99810dc739dc2814ddeae286aa2c4

5 files changed, 50 insertions, 27 deletions

diff --git a/src/expr.c b/src/expr.c
index 201dedcc8..707dfe456 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -1772,10 +1772,12 @@ static int selectNodeIsConstant(Walker *pWalker, Select *NotUsed){
 }
 static int exprIsConst(Expr *p, int initFlag, int iCur){
   Walker w;
-  memset(&w, 0, sizeof(w));
   w.eCode = initFlag;
   w.xExprCallback = exprNodeIsConstant;
   w.xSelectCallback = selectNodeIsConstant;
+#ifdef SQLITE_DEBUG
+  w.xSelectCallback2 = sqlite3SelectWalkAssert2;
+#endif
   w.u.iCur = iCur;
   sqlite3WalkExpr(&w, p);
   return w.eCode;
@@ -1863,9 +1865,9 @@ static int exprNodeIsConstantOrGroupBy(Walker *pWalker, Expr *pExpr){
 */
 int sqlite3ExprIsConstantOrGroupBy(Parse *pParse, Expr *p, ExprList *pGroupBy){
   Walker w;
-  memset(&w, 0, sizeof(w));
   w.eCode = 1;
   w.xExprCallback = exprNodeIsConstantOrGroupBy;
+  w.xSelectCallback = 0;
   w.u.pGroupBy = pGroupBy;
   w.pParse = pParse;
   sqlite3WalkExpr(&w, p);
@@ -1893,10 +1895,12 @@ int sqlite3ExprIsConstantOrFunction(Expr *p, u8 isInit){
 */
 int sqlite3ExprContainsSubquery(Expr *p){
   Walker w;
-  memset(&w, 0, sizeof(w));
   w.eCode = 1;
   w.xExprCallback = sqlite3ExprWalkNoop;
   w.xSelectCallback = selectNodeIsConstant;
+#ifdef SQLITE_DEBUG
+  w.xSelectCallback2 = sqlite3SelectWalkAssert2;
+#endif
   sqlite3WalkExpr(&w, p);
   return w.eCode==0;
 }
@@ -4901,8 +4905,8 @@ int sqlite3FunctionUsesThisSrc(Expr *pExpr, SrcList *pSrcList){
   Walker w;
   struct SrcCount cnt;
   assert( pExpr->op==TK_AGG_FUNCTION );
-  memset(&w, 0, sizeof(w));
   w.xExprCallback = exprSrcCount;
+  w.xSelectCallback = 0;
   w.u.pSrcCount = &cnt;
   cnt.pSrc = pSrcList;
   cnt.nThis = 0;
@@ -5074,10 +5078,14 @@ static int analyzeAggregate(Walker *pWalker, Expr *pExpr){
   return WRC_Continue;
 }
 static int analyzeAggregatesInSelect(Walker *pWalker, Select *pSelect){
-  UNUSED_PARAMETER(pWalker);
   UNUSED_PARAMETER(pSelect);
+  pWalker->walkerDepth++;
   return WRC_Continue;
 }
+static void analyzeAggregatesInSelectEnd(Walker *pWalker, Select *pSelect){
+  UNUSED_PARAMETER(pSelect);
+  pWalker->walkerDepth--;
+}
 
 /*
 ** Analyze the pExpr expression looking for aggregate functions and
@@ -5090,9 +5098,10 @@ static int analyzeAggregatesInSelect(Walker *pWalker, Select *pSelect){
 */
 void sqlite3ExprAnalyzeAggregates(NameContext *pNC, Expr *pExpr){
   Walker w;
-  memset(&w, 0, sizeof(w));
   w.xExprCallback = analyzeAggregate;
   w.xSelectCallback = analyzeAggregatesInSelect;
+  w.xSelectCallback2 = analyzeAggregatesInSelectEnd;
+  w.walkerDepth = 0;
   w.u.pNC = pNC;
   assert( pNC->pSrcList!=0 );
   sqlite3WalkExpr(&w, pExpr);
diff --git a/src/resolve.c b/src/resolve.c
index 6b3caa625..aed48260e 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -1446,8 +1446,6 @@ int sqlite3ResolveExprNames(
   w.xExprCallback = resolveExprStep;
   w.xSelectCallback = resolveSelectStep;
   w.xSelectCallback2 = 0;
-  w.walkerDepth = 0;
-  w.eCode = 0;
   w.u.pNC = pNC;
   sqlite3WalkExpr(&w, pExpr);
 #if SQLITE_MAX_EXPR_DEPTH>0
@@ -1501,9 +1499,9 @@ void sqlite3ResolveSelectNames(
   Walker w;
 
   assert( p!=0 );
-  memset(&w, 0, sizeof(w));
   w.xExprCallback = resolveExprStep;
   w.xSelectCallback = resolveSelectStep;
+  w.xSelectCallback2 = 0;
   w.pParse = pParse;
   w.u.pNC = pOuterNC;
   sqlite3WalkSelect(&w, p);
diff --git a/src/select.c b/src/select.c
index a8547f811..9d4c15919 100644
--- a/src/select.c
+++ b/src/select.c
@@ -4611,6 +4611,25 @@ int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
 }
 
 /*
+** No-op routine for the parse-tree walker for SELECT statements.
+** subquery in the parser tree.
+*/
+int sqlite3SelectWalkNoop(Walker *NotUsed, Select *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return WRC_Continue;
+}
+
+#if SQLITE_DEBUG
+/*
+** Always assert.  This xSelectCallback2 implementation proves that the
+** xSelectCallback2 is never invoked.
+*/
+void sqlite3SelectWalkAssert2(Walker *NotUsed, Select *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  assert( 0 );
+}
+#endif
+/*
 ** This routine "expands" a SELECT statement and all of its subqueries.
 ** For additional information on what it means to "expand" a SELECT
 ** statement, see the comment on the selectExpand worker callback above.
@@ -4625,11 +4644,11 @@ int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
 */
 static void sqlite3SelectExpand(Parse *pParse, Select *pSelect){
   Walker w;
-  memset(&w, 0, sizeof(w));
   w.xExprCallback = sqlite3ExprWalkNoop;
   w.pParse = pParse;
   if( pParse->hasCompound ){
     w.xSelectCallback = convertCompoundSelectToSubquery;
+    w.xSelectCallback2 = 0;
     sqlite3WalkSelect(&w, pSelect);
   }
   w.xSelectCallback = selectExpander;
@@ -4689,7 +4708,7 @@ static void selectAddSubqueryTypeInfo(Walker *pWalker, Select *p){
 static void sqlite3SelectAddTypeInfo(Parse *pParse, Select *pSelect){
 #ifndef SQLITE_OMIT_SUBQUERY
   Walker w;
-  memset(&w, 0, sizeof(w));
+  w.xSelectCallback = sqlite3SelectWalkNoop;
   w.xSelectCallback2 = selectAddSubqueryTypeInfo;
   w.xExprCallback = sqlite3ExprWalkNoop;
   w.pParse = pParse;
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index fc24885e2..7c78fdb42 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -3337,6 +3337,10 @@ int sqlite3WalkSelect(Walker*, Select*);
 int sqlite3WalkSelectExpr(Walker*, Select*);
 int sqlite3WalkSelectFrom(Walker*, Select*);
 int sqlite3ExprWalkNoop(Walker*, Expr*);
+int sqlite3SelectWalkNoop(Walker*, Select*);
+#ifdef SQLITE_DEBUG
+void sqlite3SelectWalkAssert2(Walker*, Select*);
+#endif
 
 /*
 ** Return code from the parse-tree walking primitives and their
diff --git a/src/walker.c b/src/walker.c
index a7123d8ab..dc874a259 100644
--- a/src/walker.c
+++ b/src/walker.c
@@ -124,8 +124,9 @@ int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
 **
 ** If it is not NULL, the xSelectCallback() callback is invoked before
 ** the walk of the expressions and FROM clause. The xSelectCallback2()
-** method, if it is not NULL, is invoked following the walk of the 
-** expressions and FROM clause.
+** method is invoked following the walk of the expressions and FROM clause,
+** but only if both xSelectCallback and xSelectCallback2 are both non-NULL
+** and if the expressions and FROM clause both return WRC_Continue;
 **
 ** Return WRC_Continue under normal conditions.  Return WRC_Abort if
 ** there is an abort request.
@@ -135,27 +136,19 @@ int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
 */
 int sqlite3WalkSelect(Walker *pWalker, Select *p){
   int rc;
-  if( p==0 || (pWalker->xSelectCallback==0 && pWalker->xSelectCallback2==0) ){
-    return WRC_Continue;
-  }
-  rc = WRC_Continue;
-  pWalker->walkerDepth++;
-  while( p ){
-    if( pWalker->xSelectCallback ){
-       rc = pWalker->xSelectCallback(pWalker, p);
-       if( rc ) break;
-    }
+  if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue;
+  do{
+    rc = pWalker->xSelectCallback(pWalker, p);
+    if( rc ) return rc & WRC_Abort;
     if( sqlite3WalkSelectExpr(pWalker, p)
      || sqlite3WalkSelectFrom(pWalker, p)
     ){
-      pWalker->walkerDepth--;
       return WRC_Abort;
     }
     if( pWalker->xSelectCallback2 ){
       pWalker->xSelectCallback2(pWalker, p);
     }
     p = p->pPrior;
-  }
-  pWalker->walkerDepth--;
-  return rc & WRC_Abort;
+  }while( p!=0 );
+  return WRC_Continue;
 }