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 ** $Id: walker.c,v 1.1 2008/08/20 16:35:10 drh Exp $ 16 */ 17 #include "sqliteInt.h" 18 #include <stdlib.h> 19 #include <string.h> 20 21 22 /* 23 ** Walk an expression tree. Invoke the callback once for each node 24 ** of the expression, while decending. (In other words, the callback 25 ** is invoked before visiting children.) 26 ** 27 ** The return value from the callback should be one of the WRC_* 28 ** constants to specify how to proceed with the walk. 29 ** 30 ** WRC_Continue Continue descending down the tree. 31 ** 32 ** WRC_Prune Do not descend into child nodes. But allow 33 ** the walk to continue with sibling nodes. 34 ** 35 ** WRC_Abort Do no more callbacks. Unwind the stack and 36 ** return the top-level walk call. 37 ** 38 ** The return value from this routine is WRC_Abort to abandon the tree walk 39 ** and WRC_Continue to continue. 40 */ 41 int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){ 42 int rc; 43 if( pExpr==0 ) return WRC_Continue; 44 rc = pWalker->xExprCallback(pWalker, pExpr); 45 if( rc==WRC_Continue ){ 46 if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort; 47 if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort; 48 if( sqlite3WalkExprList(pWalker, pExpr->pList) ) return WRC_Abort; 49 if( sqlite3WalkSelect(pWalker, pExpr->pSelect) ){ 50 return WRC_Abort; 51 } 52 } 53 return rc & WRC_Abort; 54 } 55 56 /* 57 ** Call sqlite3WalkExpr() for every expression in list p or until 58 ** an abort request is seen. 59 */ 60 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){ 61 int i, rc = WRC_Continue; 62 struct ExprList_item *pItem; 63 if( p ){ 64 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){ 65 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort; 66 } 67 } 68 return rc & WRC_Continue; 69 } 70 71 /* 72 ** Walk all expressions associated with SELECT statement p. Do 73 ** not invoke the SELECT callback on p, but do (of course) invoke 74 ** any expr callbacks and SELECT callbacks that come from subqueries. 75 ** Return WRC_Abort or WRC_Continue. 76 */ 77 int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){ 78 if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort; 79 if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort; 80 if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort; 81 if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort; 82 if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort; 83 if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort; 84 if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort; 85 return WRC_Continue; 86 } 87 88 /* 89 ** Walk the parse trees associated with all subqueries in the 90 ** FROM clause of SELECT statement p. Do not invoke the select 91 ** callback on p, but do invoke it on each FROM clause subquery 92 ** and on any subqueries further down in the tree. Return 93 ** WRC_Abort or WRC_Continue; 94 */ 95 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){ 96 SrcList *pSrc; 97 int i; 98 struct SrcList_item *pItem; 99 100 pSrc = p->pSrc; 101 if( pSrc ){ 102 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){ 103 if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){ 104 return WRC_Abort; 105 } 106 } 107 } 108 return WRC_Continue; 109 } 110 111 /* 112 ** Call sqlite3WalkExpr() for every expression in Select statement p. 113 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and 114 ** on the compound select chain, p->pPrior. 115 ** 116 ** Return WRC_Continue under normal conditions. Return WRC_Abort if 117 ** there is an abort request. 118 ** 119 ** If the Walker does not have an xSelectCallback() then this routine 120 ** is a no-op returning WRC_Continue. 121 */ 122 int sqlite3WalkSelect(Walker *pWalker, Select *p){ 123 int rc; 124 if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue; 125 rc = WRC_Continue; 126 while( p ){ 127 rc = pWalker->xSelectCallback(pWalker, p); 128 if( rc ) break; 129 if( sqlite3WalkSelectExpr(pWalker, p) ) return WRC_Abort; 130 if( sqlite3WalkSelectFrom(pWalker, p) ) return WRC_Abort; 131 p = p->pPrior; 132 } 133 return rc & WRC_Abort; 134 } 135