4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
7 ** May you do good and not evil.
8 ** May you find forgiveness for yourself and forgive others.
9 ** May you share freely, never taking more than you give.
11 *************************************************************************
12 ** This file contains routines used for walking the parser tree for
15 #include "sqliteInt.h"
21 ** Walk an expression tree. Invoke the callback once for each node
22 ** of the expression, while decending. (In other words, the callback
23 ** is invoked before visiting children.)
25 ** The return value from the callback should be one of the WRC_*
26 ** constants to specify how to proceed with the walk.
28 ** WRC_Continue Continue descending down the tree.
30 ** WRC_Prune Do not descend into child nodes. But allow
31 ** the walk to continue with sibling nodes.
33 ** WRC_Abort Do no more callbacks. Unwind the stack and
34 ** return the top-level walk call.
36 ** The return value from this routine is WRC_Abort to abandon the tree walk
37 ** and WRC_Continue to continue.
39 int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
41 if( pExpr==0 ) return WRC_Continue;
42 testcase( ExprHasProperty(pExpr, EP_TokenOnly) );
43 testcase( ExprHasProperty(pExpr, EP_Reduced) );
44 rc = pWalker->xExprCallback(pWalker, pExpr);
46 && !ExprHasAnyProperty(pExpr,EP_TokenOnly) ){
47 if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort;
48 if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort;
49 if( ExprHasProperty(pExpr, EP_xIsSelect) ){
50 if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort;
52 if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort;
55 return rc & WRC_Abort;
59 ** Call sqlite3WalkExpr() for every expression in list p or until
60 ** an abort request is seen.
62 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
64 struct ExprList_item *pItem;
66 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
67 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
74 ** Walk all expressions associated with SELECT statement p. Do
75 ** not invoke the SELECT callback on p, but do (of course) invoke
76 ** any expr callbacks and SELECT callbacks that come from subqueries.
77 ** Return WRC_Abort or WRC_Continue.
79 int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){
80 if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort;
81 if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort;
82 if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort;
83 if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort;
84 if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort;
85 if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort;
86 if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort;
91 ** Walk the parse trees associated with all subqueries in the
92 ** FROM clause of SELECT statement p. Do not invoke the select
93 ** callback on p, but do invoke it on each FROM clause subquery
94 ** and on any subqueries further down in the tree. Return
95 ** WRC_Abort or WRC_Continue;
97 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
100 struct SrcList_item *pItem;
104 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
105 if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){
114 ** Call sqlite3WalkExpr() for every expression in Select statement p.
115 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and
116 ** on the compound select chain, p->pPrior.
118 ** Return WRC_Continue under normal conditions. Return WRC_Abort if
119 ** there is an abort request.
121 ** If the Walker does not have an xSelectCallback() then this routine
122 ** is a no-op returning WRC_Continue.
124 int sqlite3WalkSelect(Walker *pWalker, Select *p){
126 if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue;
129 rc = pWalker->xSelectCallback(pWalker, p);
131 if( sqlite3WalkSelectExpr(pWalker, p) ) return WRC_Abort;
132 if( sqlite3WalkSelectFrom(pWalker, p) ) return WRC_Abort;
135 return rc & WRC_Abort;