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*/
39int 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*/
62int 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*/
79int 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*/
97int 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*/
124int 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