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 1.7 2009/06/15 23:15:59 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 testcase( ExprHasProperty(pExpr, EP_TokenOnly) ); 45 testcase( ExprHasProperty(pExpr, EP_Reduced) ); 46 rc = pWalker->xExprCallback(pWalker, pExpr); 47 if( rc==WRC_Continue 48 && !ExprHasAnyProperty(pExpr,EP_TokenOnly) ){ 49 if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort; 50 if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort; 51 if( ExprHasProperty(pExpr, EP_xIsSelect) ){ 52 if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort; 53 }else{ 54 if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort; 55 } 56 } 57 return rc & WRC_Abort; 58 } 59 60 /* 61 ** Call sqlite3WalkExpr() for every expression in list p or until 62 ** an abort request is seen. 63 */ 64 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){ 65 int i; 66 struct ExprList_item *pItem; 67 if( p ){ 68 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){ 69 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort; 70 } 71 } 72 return WRC_Continue; 73 } 74 75 /* 76 ** Walk all expressions associated with SELECT statement p. Do 77 ** not invoke the SELECT callback on p, but do (of course) invoke 78 ** any expr callbacks and SELECT callbacks that come from subqueries. 79 ** Return WRC_Abort or WRC_Continue. 80 */ 81 int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){ 82 if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort; 83 if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort; 84 if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort; 85 if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort; 86 if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort; 87 if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort; 88 if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort; 89 return WRC_Continue; 90 } 91 92 /* 93 ** Walk the parse trees associated with all subqueries in the 94 ** FROM clause of SELECT statement p. Do not invoke the select 95 ** callback on p, but do invoke it on each FROM clause subquery 96 ** and on any subqueries further down in the tree. Return 97 ** WRC_Abort or WRC_Continue; 98 */ 99 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){ 100 SrcList *pSrc; 101 int i; 102 struct SrcList_item *pItem; 103 104 pSrc = p->pSrc; 105 if( ALWAYS(pSrc) ){ 106 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){ 107 if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){ 108 return WRC_Abort; 109 } 110 } 111 } 112 return WRC_Continue; 113 } 114 115 /* 116 ** Call sqlite3WalkExpr() for every expression in Select statement p. 117 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and 118 ** on the compound select chain, p->pPrior. 119 ** 120 ** Return WRC_Continue under normal conditions. Return WRC_Abort if 121 ** there is an abort request. 122 ** 123 ** If the Walker does not have an xSelectCallback() then this routine 124 ** is a no-op returning WRC_Continue. 125 */ 126 int sqlite3WalkSelect(Walker *pWalker, Select *p){ 127 int rc; 128 if( p==0 || pWalker->xSelectCallback==0 ) return WRC_Continue; 129 rc = WRC_Continue; 130 while( p ){ 131 rc = pWalker->xSelectCallback(pWalker, p); 132 if( rc ) break; 133 if( sqlite3WalkSelectExpr(pWalker, p) ) return WRC_Abort; 134 if( sqlite3WalkSelectFrom(pWalker, p) ) return WRC_Abort; 135 p = p->pPrior; 136 } 137 return rc & WRC_Abort; 138 } 139