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 decending. (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 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 int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){ 40 int rc; 41 if( pExpr==0 ) return WRC_Continue; 42 testcase( ExprHasProperty(pExpr, EP_TokenOnly) ); 43 testcase( ExprHasProperty(pExpr, EP_Reduced) ); 44 rc = pWalker->xExprCallback(pWalker, pExpr); 45 if( rc==WRC_Continue 46 && !ExprHasAnyProperty(pExpr,EP_TokenOnly) ){ 47 if( sqlite3WalkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort; 48 if( sqlite3WalkExpr(pWalker, pExpr->pRight) ) return WRC_Abort; 49 if( ExprHasProperty(pExpr, EP_xIsSelect) ){ 50 if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort; 51 }else{ 52 if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort; 53 } 54 } 55 return rc & WRC_Abort; 56 } 57 58 /* 59 ** Call sqlite3WalkExpr() for every expression in list p or until 60 ** an abort request is seen. 61 */ 62 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){ 63 int i; 64 struct ExprList_item *pItem; 65 if( p ){ 66 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){ 67 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort; 68 } 69 } 70 return WRC_Continue; 71 } 72 73 /* 74 ** Walk all expressions associated with SELECT statement p. Do 75 ** not invoke the SELECT callback on p, but do (of course) invoke 76 ** any expr callbacks and SELECT callbacks that come from subqueries. 77 ** Return WRC_Abort or WRC_Continue. 78 */ 79 int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){ 80 if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort; 81 if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort; 82 if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort; 83 if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort; 84 if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort; 85 if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort; 86 if( sqlite3WalkExpr(pWalker, p->pOffset) ) return WRC_Abort; 87 return WRC_Continue; 88 } 89 90 /* 91 ** Walk the parse trees associated with all subqueries in the 92 ** FROM clause of SELECT statement p. Do not invoke the select 93 ** callback on p, but do invoke it on each FROM clause subquery 94 ** and on any subqueries further down in the tree. Return 95 ** WRC_Abort or WRC_Continue; 96 */ 97 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){ 98 SrcList *pSrc; 99 int i; 100 struct SrcList_item *pItem; 101 102 pSrc = p->pSrc; 103 if( ALWAYS(pSrc) ){ 104 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){ 105 if( sqlite3WalkSelect(pWalker, pItem->pSelect) ){ 106 return WRC_Abort; 107 } 108 } 109 } 110 return WRC_Continue; 111 } 112 113 /* 114 ** Call sqlite3WalkExpr() for every expression in Select statement p. 115 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and 116 ** on the compound select chain, p->pPrior. Invoke the xSelectCallback() 117 ** either before or after the walk of expressions and FROM clause, depending 118 ** on whether pWalker->bSelectDepthFirst is false or true, respectively. 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 pWalker->walkerDepth++; 131 while( p ){ 132 if( !pWalker->bSelectDepthFirst ){ 133 rc = pWalker->xSelectCallback(pWalker, p); 134 if( rc ) break; 135 } 136 if( sqlite3WalkSelectExpr(pWalker, p) 137 || sqlite3WalkSelectFrom(pWalker, p) 138 ){ 139 pWalker->walkerDepth--; 140 return WRC_Abort; 141 } 142 if( pWalker->bSelectDepthFirst ){ 143 rc = pWalker->xSelectCallback(pWalker, p); 144 /* Depth-first search is currently only used for 145 ** selectAddSubqueryTypeInfo() and that routine always returns 146 ** WRC_Continue (0). So the following branch is never taken. */ 147 if( NEVER(rc) ) break; 148 } 149 p = p->pPrior; 150 } 151 pWalker->walkerDepth--; 152 return rc & WRC_Abort; 153 } 154