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 descending. (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 from 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 */ 39 static SQLITE_NOINLINE int walkExpr(Walker *pWalker, Expr *pExpr){ 40 int rc; 41 testcase( ExprHasProperty(pExpr, EP_TokenOnly) ); 42 testcase( ExprHasProperty(pExpr, EP_Reduced) ); 43 while(1){ 44 rc = pWalker->xExprCallback(pWalker, pExpr); 45 if( rc ) return rc & WRC_Abort; 46 if( !ExprHasProperty(pExpr,(EP_TokenOnly|EP_Leaf)) ){ 47 if( pExpr->pLeft && walkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort; 48 assert( pExpr->x.pList==0 || pExpr->pRight==0 ); 49 if( pExpr->pRight ){ 50 pExpr = pExpr->pRight; 51 continue; 52 }else if( ExprHasProperty(pExpr, EP_xIsSelect) ){ 53 if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort; 54 }else if( pExpr->x.pList ){ 55 if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort; 56 } 57 } 58 break; 59 } 60 return WRC_Continue; 61 } 62 int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){ 63 return pExpr ? walkExpr(pWalker,pExpr) : WRC_Continue; 64 } 65 66 /* 67 ** Call sqlite3WalkExpr() for every expression in list p or until 68 ** an abort request is seen. 69 */ 70 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){ 71 int i; 72 struct ExprList_item *pItem; 73 if( p ){ 74 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){ 75 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort; 76 } 77 } 78 return WRC_Continue; 79 } 80 81 /* 82 ** Walk all expressions associated with SELECT statement p. Do 83 ** not invoke the SELECT callback on p, but do (of course) invoke 84 ** any expr callbacks and SELECT callbacks that come from subqueries. 85 ** Return WRC_Abort or WRC_Continue. 86 */ 87 int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){ 88 if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort; 89 if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort; 90 if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort; 91 if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort; 92 if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort; 93 if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort; 94 return WRC_Continue; 95 } 96 97 /* 98 ** Walk the parse trees associated with all subqueries in the 99 ** FROM clause of SELECT statement p. Do not invoke the select 100 ** callback on p, but do invoke it on each FROM clause subquery 101 ** and on any subqueries further down in the tree. Return 102 ** WRC_Abort or WRC_Continue; 103 */ 104 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){ 105 SrcList *pSrc; 106 int i; 107 struct SrcList_item *pItem; 108 109 pSrc = p->pSrc; 110 assert( pSrc!=0 ); 111 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){ 112 if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){ 113 return WRC_Abort; 114 } 115 if( pItem->fg.isTabFunc 116 && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg) 117 ){ 118 return WRC_Abort; 119 } 120 } 121 return WRC_Continue; 122 } 123 124 /* 125 ** Call sqlite3WalkExpr() for every expression in Select statement p. 126 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and 127 ** on the compound select chain, p->pPrior. 128 ** 129 ** If it is not NULL, the xSelectCallback() callback is invoked before 130 ** the walk of the expressions and FROM clause. The xSelectCallback2() 131 ** method is invoked following the walk of the expressions and FROM clause, 132 ** but only if both xSelectCallback and xSelectCallback2 are both non-NULL 133 ** and if the expressions and FROM clause both return WRC_Continue; 134 ** 135 ** Return WRC_Continue under normal conditions. Return WRC_Abort if 136 ** there is an abort request. 137 ** 138 ** If the Walker does not have an xSelectCallback() then this routine 139 ** is a no-op returning WRC_Continue. 140 */ 141 int sqlite3WalkSelect(Walker *pWalker, Select *p){ 142 int rc; 143 if( p==0 ) return WRC_Continue; 144 if( pWalker->xSelectCallback==0 ) return WRC_Continue; 145 do{ 146 rc = pWalker->xSelectCallback(pWalker, p); 147 if( rc ) return rc & WRC_Abort; 148 if( sqlite3WalkSelectExpr(pWalker, p) 149 || sqlite3WalkSelectFrom(pWalker, p) 150 ){ 151 return WRC_Abort; 152 } 153 if( pWalker->xSelectCallback2 ){ 154 pWalker->xSelectCallback2(pWalker, p); 155 } 156 p = p->pPrior; 157 }while( p!=0 ); 158 return WRC_Continue; 159 } 160