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