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 #if !defined(SQLITE_OMIT_WINDOWFUNC) 21 /* 22 ** Walk all expressions linked into the list of Window objects passed 23 ** as the second argument. 24 */ 25 static int walkWindowList(Walker *pWalker, Window *pList, int bOneOnly){ 26 Window *pWin; 27 for(pWin=pList; pWin; pWin=pWin->pNextWin){ 28 int rc; 29 rc = sqlite3WalkExprList(pWalker, pWin->pOrderBy); 30 if( rc ) return WRC_Abort; 31 rc = sqlite3WalkExprList(pWalker, pWin->pPartition); 32 if( rc ) return WRC_Abort; 33 rc = sqlite3WalkExpr(pWalker, pWin->pFilter); 34 if( rc ) return WRC_Abort; 35 rc = sqlite3WalkExpr(pWalker, pWin->pStart); 36 if( rc ) return WRC_Abort; 37 rc = sqlite3WalkExpr(pWalker, pWin->pEnd); 38 if( rc ) return WRC_Abort; 39 if( bOneOnly ) break; 40 } 41 return WRC_Continue; 42 } 43 #endif 44 45 /* 46 ** Walk an expression tree. Invoke the callback once for each node 47 ** of the expression, while descending. (In other words, the callback 48 ** is invoked before visiting children.) 49 ** 50 ** The return value from the callback should be one of the WRC_* 51 ** constants to specify how to proceed with the walk. 52 ** 53 ** WRC_Continue Continue descending down the tree. 54 ** 55 ** WRC_Prune Do not descend into child nodes, but allow 56 ** the walk to continue with sibling nodes. 57 ** 58 ** WRC_Abort Do no more callbacks. Unwind the stack and 59 ** return from the top-level walk call. 60 ** 61 ** The return value from this routine is WRC_Abort to abandon the tree walk 62 ** and WRC_Continue to continue. 63 */ 64 static SQLITE_NOINLINE int walkExpr(Walker *pWalker, Expr *pExpr){ 65 int rc; 66 testcase( ExprHasProperty(pExpr, EP_TokenOnly) ); 67 testcase( ExprHasProperty(pExpr, EP_Reduced) ); 68 while(1){ 69 rc = pWalker->xExprCallback(pWalker, pExpr); 70 if( rc ) return rc & WRC_Abort; 71 if( !ExprHasProperty(pExpr,(EP_TokenOnly|EP_Leaf)) ){ 72 assert( pExpr->x.pList==0 || pExpr->pRight==0 ); 73 if( pExpr->pLeft && walkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort; 74 if( pExpr->pRight ){ 75 assert( !ExprHasProperty(pExpr, EP_WinFunc) ); 76 pExpr = pExpr->pRight; 77 continue; 78 }else if( ExprHasProperty(pExpr, EP_xIsSelect) ){ 79 assert( !ExprHasProperty(pExpr, EP_WinFunc) ); 80 if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort; 81 }else{ 82 if( pExpr->x.pList ){ 83 if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort; 84 } 85 #ifndef SQLITE_OMIT_WINDOWFUNC 86 if( ExprHasProperty(pExpr, EP_WinFunc) ){ 87 if( walkWindowList(pWalker, pExpr->y.pWin, 1) ) return WRC_Abort; 88 } 89 #endif 90 } 91 } 92 break; 93 } 94 return WRC_Continue; 95 } 96 int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){ 97 return pExpr ? walkExpr(pWalker,pExpr) : WRC_Continue; 98 } 99 100 /* 101 ** Call sqlite3WalkExpr() for every expression in list p or until 102 ** an abort request is seen. 103 */ 104 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){ 105 int i; 106 struct ExprList_item *pItem; 107 if( p ){ 108 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){ 109 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort; 110 } 111 } 112 return WRC_Continue; 113 } 114 115 /* 116 ** This is a no-op callback for Walker->xSelectCallback2. If this 117 ** callback is set, then the Select->pWinDefn list is traversed. 118 */ 119 void sqlite3WalkWinDefnDummyCallback(Walker *pWalker, Select *p){ 120 UNUSED_PARAMETER(pWalker); 121 UNUSED_PARAMETER(p); 122 /* No-op */ 123 } 124 125 /* 126 ** Walk all expressions associated with SELECT statement p. Do 127 ** not invoke the SELECT callback on p, but do (of course) invoke 128 ** any expr callbacks and SELECT callbacks that come from subqueries. 129 ** Return WRC_Abort or WRC_Continue. 130 */ 131 int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){ 132 if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort; 133 if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort; 134 if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort; 135 if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort; 136 if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort; 137 if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort; 138 #if !defined(SQLITE_OMIT_WINDOWFUNC) 139 if( p->pWinDefn ){ 140 Parse *pParse; 141 if( pWalker->xSelectCallback2==sqlite3WalkWinDefnDummyCallback 142 || ((pParse = pWalker->pParse)!=0 && IN_RENAME_OBJECT) 143 ){ 144 /* The following may return WRC_Abort if there are unresolvable 145 ** symbols (e.g. a table that does not exist) in a window definition. */ 146 int rc = walkWindowList(pWalker, p->pWinDefn, 0); 147 return rc; 148 } 149 } 150 #endif 151 return WRC_Continue; 152 } 153 154 /* 155 ** Walk the parse trees associated with all subqueries in the 156 ** FROM clause of SELECT statement p. Do not invoke the select 157 ** callback on p, but do invoke it on each FROM clause subquery 158 ** and on any subqueries further down in the tree. Return 159 ** WRC_Abort or WRC_Continue; 160 */ 161 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){ 162 SrcList *pSrc; 163 int i; 164 SrcItem *pItem; 165 166 pSrc = p->pSrc; 167 if( ALWAYS(pSrc) ){ 168 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){ 169 if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){ 170 return WRC_Abort; 171 } 172 if( pItem->fg.isTabFunc 173 && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg) 174 ){ 175 return WRC_Abort; 176 } 177 } 178 } 179 return WRC_Continue; 180 } 181 182 /* 183 ** Call sqlite3WalkExpr() for every expression in Select statement p. 184 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and 185 ** on the compound select chain, p->pPrior. 186 ** 187 ** If it is not NULL, the xSelectCallback() callback is invoked before 188 ** the walk of the expressions and FROM clause. The xSelectCallback2() 189 ** method is invoked following the walk of the expressions and FROM clause, 190 ** but only if both xSelectCallback and xSelectCallback2 are both non-NULL 191 ** and if the expressions and FROM clause both return WRC_Continue; 192 ** 193 ** Return WRC_Continue under normal conditions. Return WRC_Abort if 194 ** there is an abort request. 195 ** 196 ** If the Walker does not have an xSelectCallback() then this routine 197 ** is a no-op returning WRC_Continue. 198 */ 199 int sqlite3WalkSelect(Walker *pWalker, Select *p){ 200 int rc; 201 if( p==0 ) return WRC_Continue; 202 if( pWalker->xSelectCallback==0 ) return WRC_Continue; 203 do{ 204 rc = pWalker->xSelectCallback(pWalker, p); 205 if( rc ) return rc & WRC_Abort; 206 if( sqlite3WalkSelectExpr(pWalker, p) 207 || sqlite3WalkSelectFrom(pWalker, p) 208 ){ 209 return WRC_Abort; 210 } 211 if( pWalker->xSelectCallback2 ){ 212 pWalker->xSelectCallback2(pWalker, p); 213 } 214 p = p->pPrior; 215 }while( p!=0 ); 216 return WRC_Continue; 217 } 218 219 /* Increase the walkerDepth when entering a subquery, and 220 ** descrease when leaving the subquery. 221 */ 222 int sqlite3WalkerDepthIncrease(Walker *pWalker, Select *pSelect){ 223 UNUSED_PARAMETER(pSelect); 224 pWalker->walkerDepth++; 225 return WRC_Continue; 226 } 227 void sqlite3WalkerDepthDecrease(Walker *pWalker, Select *pSelect){ 228 UNUSED_PARAMETER(pSelect); 229 pWalker->walkerDepth--; 230 } 231 232 233 /* 234 ** No-op routine for the parse-tree walker. 235 ** 236 ** When this routine is the Walker.xExprCallback then expression trees 237 ** are walked without any actions being taken at each node. Presumably, 238 ** when this routine is used for Walker.xExprCallback then 239 ** Walker.xSelectCallback is set to do something useful for every 240 ** subquery in the parser tree. 241 */ 242 int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){ 243 UNUSED_PARAMETER2(NotUsed, NotUsed2); 244 return WRC_Continue; 245 } 246 247 /* 248 ** No-op routine for the parse-tree walker for SELECT statements. 249 ** subquery in the parser tree. 250 */ 251 int sqlite3SelectWalkNoop(Walker *NotUsed, Select *NotUsed2){ 252 UNUSED_PARAMETER2(NotUsed, NotUsed2); 253 return WRC_Continue; 254 } 255