1 files changed, 259 insertions, 0 deletions
diff --git a/src/walker.c b/src/walker.c
new file mode 100644
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+++ b/src/walker.c
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+/*
+** 2008 August 16
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains routines used for walking the parser tree for
+** an SQL statement.
+*/
+#include "sqliteInt.h"
+#include <stdlib.h>
+#include <string.h>
+
+
+#if !defined(SQLITE_OMIT_WINDOWFUNC)
+/*
+** Walk all expressions linked into the list of Window objects passed
+** as the second argument.
+*/
+static int walkWindowList(Walker *pWalker, Window *pList, int bOneOnly){
+  Window *pWin;
+  for(pWin=pList; pWin; pWin=pWin->pNextWin){
+    int rc;
+    rc = sqlite3WalkExprList(pWalker, pWin->pOrderBy);
+    if( rc ) return WRC_Abort;
+    rc = sqlite3WalkExprList(pWalker, pWin->pPartition);
+    if( rc ) return WRC_Abort;
+    rc = sqlite3WalkExpr(pWalker, pWin->pFilter);
+    if( rc ) return WRC_Abort;
+    rc = sqlite3WalkExpr(pWalker, pWin->pStart);
+    if( rc ) return WRC_Abort;
+    rc = sqlite3WalkExpr(pWalker, pWin->pEnd);
+    if( rc ) return WRC_Abort;
+    if( bOneOnly ) break;
+  }
+  return WRC_Continue;
+}
+#endif
+
+/*
+** Walk an expression tree.  Invoke the callback once for each node
+** of the expression, while descending.  (In other words, the callback
+** is invoked before visiting children.)
+**
+** The return value from the callback should be one of the WRC_*
+** constants to specify how to proceed with the walk.
+**
+**    WRC_Continue      Continue descending down the tree.
+**
+**    WRC_Prune         Do not descend into child nodes, but allow
+**                      the walk to continue with sibling nodes.
+**
+**    WRC_Abort         Do no more callbacks.  Unwind the stack and
+**                      return from the top-level walk call.
+**
+** The return value from this routine is WRC_Abort to abandon the tree walk
+** and WRC_Continue to continue.
+*/
+SQLITE_NOINLINE int sqlite3WalkExprNN(Walker *pWalker, Expr *pExpr){
+  int rc;
+  testcase( ExprHasProperty(pExpr, EP_TokenOnly) );
+  testcase( ExprHasProperty(pExpr, EP_Reduced) );
+  while(1){
+    rc = pWalker->xExprCallback(pWalker, pExpr);
+    if( rc ) return rc & WRC_Abort;
+    if( !ExprHasProperty(pExpr,(EP_TokenOnly|EP_Leaf)) ){
+      assert( pExpr->x.pList==0 || pExpr->pRight==0 );
+      if( pExpr->pLeft && sqlite3WalkExprNN(pWalker, pExpr->pLeft) ){
+        return WRC_Abort;
+      }
+      if( pExpr->pRight ){
+        assert( !ExprHasProperty(pExpr, EP_WinFunc) );
+        pExpr = pExpr->pRight;
+        continue;
+      }else if( ExprUseXSelect(pExpr) ){
+        assert( !ExprHasProperty(pExpr, EP_WinFunc) );
+        if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort;
+      }else{
+        if( pExpr->x.pList ){
+          if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort;
+        }
+#ifndef SQLITE_OMIT_WINDOWFUNC
+        if( ExprHasProperty(pExpr, EP_WinFunc) ){
+          if( walkWindowList(pWalker, pExpr->y.pWin, 1) ) return WRC_Abort;
+        }
+#endif
+      }
+    }
+    break;
+  }
+  return WRC_Continue;
+}
+int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
+  return pExpr ? sqlite3WalkExprNN(pWalker,pExpr) : WRC_Continue;
+}
+
+/*
+** Call sqlite3WalkExpr() for every expression in list p or until
+** an abort request is seen.
+*/
+int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
+  int i;
+  struct ExprList_item *pItem;
+  if( p ){
+    for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
+      if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** This is a no-op callback for Walker->xSelectCallback2.  If this
+** callback is set, then the Select->pWinDefn list is traversed.
+*/
+void sqlite3WalkWinDefnDummyCallback(Walker *pWalker, Select *p){
+  UNUSED_PARAMETER(pWalker);
+  UNUSED_PARAMETER(p);
+  /* No-op */
+}
+
+/*
+** Walk all expressions associated with SELECT statement p.  Do
+** not invoke the SELECT callback on p, but do (of course) invoke
+** any expr callbacks and SELECT callbacks that come from subqueries.
+** Return WRC_Abort or WRC_Continue.
+*/
+int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
+  if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
+  if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
+  if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
+  if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
+#if !defined(SQLITE_OMIT_WINDOWFUNC)
+  if( p->pWinDefn ){
+    Parse *pParse;
+    if( pWalker->xSelectCallback2==sqlite3WalkWinDefnDummyCallback
+     || ((pParse = pWalker->pParse)!=0 && IN_RENAME_OBJECT)
+#ifndef SQLITE_OMIT_CTE
+     || pWalker->xSelectCallback2==sqlite3SelectPopWith
+#endif
+    ){
+      /* The following may return WRC_Abort if there are unresolvable
+      ** symbols (e.g. a table that does not exist) in a window definition. */
+      int rc = walkWindowList(pWalker, p->pWinDefn, 0);
+      return rc;
+    }
+  }
+#endif
+  return WRC_Continue;
+}
+
+/*
+** Walk the parse trees associated with all subqueries in the
+** FROM clause of SELECT statement p.  Do not invoke the select
+** callback on p, but do invoke it on each FROM clause subquery
+** and on any subqueries further down in the tree.  Return 
+** WRC_Abort or WRC_Continue;
+*/
+int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
+  SrcList *pSrc;
+  int i;
+  SrcItem *pItem;
+
+  pSrc = p->pSrc;
+  if( ALWAYS(pSrc) ){
+    for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
+      if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){
+        return WRC_Abort;
+      }
+      if( pItem->fg.isTabFunc
+       && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg)
+      ){
+        return WRC_Abort;
+      }
+    }
+  }
+  return WRC_Continue;
+}
+
+/*
+** Call sqlite3WalkExpr() for every expression in Select statement p.
+** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and
+** on the compound select chain, p->pPrior. 
+**
+** If it is not NULL, the xSelectCallback() callback is invoked before
+** the walk of the expressions and FROM clause. The xSelectCallback2()
+** 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.
+**
+** If the Walker does not have an xSelectCallback() then this routine
+** is a no-op returning WRC_Continue.
+*/
+int sqlite3WalkSelect(Walker *pWalker, Select *p){
+  int rc;
+  if( p==0 ) return WRC_Continue;
+  if( 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)
+    ){
+      return WRC_Abort;
+    }
+    if( pWalker->xSelectCallback2 ){
+      pWalker->xSelectCallback2(pWalker, p);
+    }
+    p = p->pPrior;
+  }while( p!=0 );
+  return WRC_Continue;
+}
+
+/* Increase the walkerDepth when entering a subquery, and
+** decrease when leaving the subquery.
+*/
+int sqlite3WalkerDepthIncrease(Walker *pWalker, Select *pSelect){
+  UNUSED_PARAMETER(pSelect);
+  pWalker->walkerDepth++;
+  return WRC_Continue;
+}
+void sqlite3WalkerDepthDecrease(Walker *pWalker, Select *pSelect){
+  UNUSED_PARAMETER(pSelect);
+  pWalker->walkerDepth--;
+}
+
+
+/*
+** No-op routine for the parse-tree walker.
+**
+** When this routine is the Walker.xExprCallback then expression trees
+** are walked without any actions being taken at each node.  Presumably,
+** when this routine is used for Walker.xExprCallback then 
+** Walker.xSelectCallback is set to do something useful for every 
+** subquery in the parser tree.
+*/
+int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
+  UNUSED_PARAMETER2(NotUsed, NotUsed2);
+  return WRC_Continue;
+}
+
+/*
+** 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;
+}