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 if( pExpr->pWin ){ 58 Window *pWin = pExpr->pWin; 59 if( sqlite3WalkExprList(pWalker, pWin->pPartition) ) return WRC_Abort; 60 if( sqlite3WalkExprList(pWalker, pWin->pOrderBy) ) return WRC_Abort; 61 if( sqlite3WalkExpr(pWalker, pWin->pFilter) ) return WRC_Abort; 62 } 63 } 64 break; 65 } 66 return WRC_Continue; 67 } 68 int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){ 69 return pExpr ? walkExpr(pWalker,pExpr) : WRC_Continue; 70 } 71 72 /* 73 ** Call sqlite3WalkExpr() for every expression in list p or until 74 ** an abort request is seen. 75 */ 76 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){ 77 int i; 78 struct ExprList_item *pItem; 79 if( p ){ 80 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){ 81 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort; 82 } 83 } 84 return WRC_Continue; 85 } 86 87 /* 88 ** Walk all expressions associated with SELECT statement p. Do 89 ** not invoke the SELECT callback on p, but do (of course) invoke 90 ** any expr callbacks and SELECT callbacks that come from subqueries. 91 ** Return WRC_Abort or WRC_Continue. 92 */ 93 int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){ 94 if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort; 95 if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort; 96 if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort; 97 if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort; 98 if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort; 99 if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort; 100 return WRC_Continue; 101 } 102 103 /* 104 ** Walk the parse trees associated with all subqueries in the 105 ** FROM clause of SELECT statement p. Do not invoke the select 106 ** callback on p, but do invoke it on each FROM clause subquery 107 ** and on any subqueries further down in the tree. Return 108 ** WRC_Abort or WRC_Continue; 109 */ 110 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){ 111 SrcList *pSrc; 112 int i; 113 struct SrcList_item *pItem; 114 115 pSrc = p->pSrc; 116 assert( pSrc!=0 ); 117 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){ 118 if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){ 119 return WRC_Abort; 120 } 121 if( pItem->fg.isTabFunc 122 && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg) 123 ){ 124 return WRC_Abort; 125 } 126 } 127 return WRC_Continue; 128 } 129 130 /* 131 ** Call sqlite3WalkExpr() for every expression in Select statement p. 132 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and 133 ** on the compound select chain, p->pPrior. 134 ** 135 ** If it is not NULL, the xSelectCallback() callback is invoked before 136 ** the walk of the expressions and FROM clause. The xSelectCallback2() 137 ** method is invoked following the walk of the expressions and FROM clause, 138 ** but only if both xSelectCallback and xSelectCallback2 are both non-NULL 139 ** and if the expressions and FROM clause both return WRC_Continue; 140 ** 141 ** Return WRC_Continue under normal conditions. Return WRC_Abort if 142 ** there is an abort request. 143 ** 144 ** If the Walker does not have an xSelectCallback() then this routine 145 ** is a no-op returning WRC_Continue. 146 */ 147 int sqlite3WalkSelect(Walker *pWalker, Select *p){ 148 int rc; 149 if( p==0 ) return WRC_Continue; 150 if( pWalker->xSelectCallback==0 ) return WRC_Continue; 151 do{ 152 rc = pWalker->xSelectCallback(pWalker, p); 153 if( rc ) return rc & WRC_Abort; 154 if( sqlite3WalkSelectExpr(pWalker, p) 155 || sqlite3WalkSelectFrom(pWalker, p) 156 ){ 157 return WRC_Abort; 158 } 159 if( pWalker->xSelectCallback2 ){ 160 pWalker->xSelectCallback2(pWalker, p); 161 } 162 p = p->pPrior; 163 }while( p!=0 ); 164 return WRC_Continue; 165 } 166