1 /*
2 ** 2008 August 16
3 **
4 ** The author disclaims copyright to this source code. In place of
5 ** a legal notice, here is a blessing:
6 **
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.
10 **
11 *************************************************************************
12 ** This file contains routines used for walking the parser tree for
13 ** an SQL statement.
14 */
15 #include "sqliteInt.h"
16 #include <stdlib.h>
17 #include <string.h>
18
19
20 /*
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.)
24 **
25 ** The return value from the callback should be one of the WRC_*
26 ** constants to specify how to proceed with the walk.
27 **
28 ** WRC_Continue Continue descending down the tree.
29 **
30 ** WRC_Prune Do not descend into child nodes. But allow
31 ** the walk to continue with sibling nodes.
32 **
33 ** WRC_Abort Do no more callbacks. Unwind the stack and
34 ** return the top-level walk call.
35 **
36 ** The return value from this routine is WRC_Abort to abandon the tree walk
37 ** and WRC_Continue to continue.
38 */
sqlite3WalkExpr(Walker * pWalker,Expr * pExpr)39 int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){
40 int rc;
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);
45 if( rc==WRC_Continue
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;
51 }else{
52 if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort;
53 }
54 }
55 return rc & WRC_Abort;
56 }
57
58 /*
59 ** Call sqlite3WalkExpr() for every expression in list p or until
60 ** an abort request is seen.
61 */
sqlite3WalkExprList(Walker * pWalker,ExprList * p)62 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){
63 int i;
64 struct ExprList_item *pItem;
65 if( p ){
66 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){
67 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort;
68 }
69 }
70 return WRC_Continue;
71 }
72
73 /*
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.
78 */
sqlite3WalkSelectExpr(Walker * pWalker,Select * p)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;
87 return WRC_Continue;
88 }
89
90 /*
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;
96 */
sqlite3WalkSelectFrom(Walker * pWalker,Select * p)97 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
98 SrcList *pSrc;
99 int i;
100 struct SrcList_item *pItem;
101
102 pSrc = p->pSrc;
103 if( ALWAYS(pSrc) ){
104 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
105 if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){
106 return WRC_Abort;
107 }
108 }
109 }
110 return WRC_Continue;
111 }
112
113 /*
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.
117 **
118 ** Return WRC_Continue under normal conditions. Return WRC_Abort if
119 ** there is an abort request.
120 **
121 ** If the Walker does not have an xSelectCallback() then this routine
122 ** is a no-op returning WRC_Continue.
123 */
sqlite3WalkSelect(Walker * pWalker,Select * p)124 int sqlite3WalkSelect(Walker *pWalker, Select *p){
125 int rc;
126 if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue;
127 rc = WRC_Continue;
128 while( p ){
129 rc = pWalker->xSelectCallback(pWalker, p);
130 if( rc ) break;
131 if( sqlite3WalkSelectExpr(pWalker, p) ) return WRC_Abort;
132 if( sqlite3WalkSelectFrom(pWalker, p) ) return WRC_Abort;
133 p = p->pPrior;
134 }
135 return rc & WRC_Abort;
136 }
137