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