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 36 /* The next two are purely for calls to sqlite3RenameExprUnmap() 37 ** within sqlite3WindowOffsetExpr(). Because of constraints imposed 38 ** by sqlite3WindowOffsetExpr(), they can never fail. The results do 39 ** not matter anyhow. */ 40 rc = sqlite3WalkExpr(pWalker, pWin->pStart); 41 if( NEVER(rc) ) return WRC_Abort; 42 rc = sqlite3WalkExpr(pWalker, pWin->pEnd); 43 if( NEVER(rc) ) return WRC_Abort; 44 if( bOneOnly ) break; 45 } 46 return WRC_Continue; 47 } 48 #endif 49 50 /* 51 ** Walk an expression tree. Invoke the callback once for each node 52 ** of the expression, while descending. (In other words, the callback 53 ** is invoked before visiting children.) 54 ** 55 ** The return value from the callback should be one of the WRC_* 56 ** constants to specify how to proceed with the walk. 57 ** 58 ** WRC_Continue Continue descending down the tree. 59 ** 60 ** WRC_Prune Do not descend into child nodes, but allow 61 ** the walk to continue with sibling nodes. 62 ** 63 ** WRC_Abort Do no more callbacks. Unwind the stack and 64 ** return from the top-level walk call. 65 ** 66 ** The return value from this routine is WRC_Abort to abandon the tree walk 67 ** and WRC_Continue to continue. 68 */ 69 static SQLITE_NOINLINE int walkExpr(Walker *pWalker, Expr *pExpr){ 70 int rc; 71 testcase( ExprHasProperty(pExpr, EP_TokenOnly) ); 72 testcase( ExprHasProperty(pExpr, EP_Reduced) ); 73 while(1){ 74 rc = pWalker->xExprCallback(pWalker, pExpr); 75 if( rc ) return rc & WRC_Abort; 76 if( !ExprHasProperty(pExpr,(EP_TokenOnly|EP_Leaf)) ){ 77 assert( pExpr->x.pList==0 || pExpr->pRight==0 ); 78 if( pExpr->pLeft && walkExpr(pWalker, pExpr->pLeft) ) return WRC_Abort; 79 if( pExpr->pRight ){ 80 assert( !ExprHasProperty(pExpr, EP_WinFunc) ); 81 pExpr = pExpr->pRight; 82 continue; 83 }else if( ExprHasProperty(pExpr, EP_xIsSelect) ){ 84 assert( !ExprHasProperty(pExpr, EP_WinFunc) ); 85 if( sqlite3WalkSelect(pWalker, pExpr->x.pSelect) ) return WRC_Abort; 86 }else{ 87 if( pExpr->x.pList ){ 88 if( sqlite3WalkExprList(pWalker, pExpr->x.pList) ) return WRC_Abort; 89 } 90 #ifndef SQLITE_OMIT_WINDOWFUNC 91 if( ExprHasProperty(pExpr, EP_WinFunc) ){ 92 if( walkWindowList(pWalker, pExpr->y.pWin, 1) ) return WRC_Abort; 93 } 94 #endif 95 } 96 } 97 break; 98 } 99 return WRC_Continue; 100 } 101 int sqlite3WalkExpr(Walker *pWalker, Expr *pExpr){ 102 return pExpr ? walkExpr(pWalker,pExpr) : WRC_Continue; 103 } 104 105 /* 106 ** Call sqlite3WalkExpr() for every expression in list p or until 107 ** an abort request is seen. 108 */ 109 int sqlite3WalkExprList(Walker *pWalker, ExprList *p){ 110 int i; 111 struct ExprList_item *pItem; 112 if( p ){ 113 for(i=p->nExpr, pItem=p->a; i>0; i--, pItem++){ 114 if( sqlite3WalkExpr(pWalker, pItem->pExpr) ) return WRC_Abort; 115 } 116 } 117 return WRC_Continue; 118 } 119 120 /* 121 ** Walk all expressions associated with SELECT statement p. Do 122 ** not invoke the SELECT callback on p, but do (of course) invoke 123 ** any expr callbacks and SELECT callbacks that come from subqueries. 124 ** Return WRC_Abort or WRC_Continue. 125 */ 126 int sqlite3WalkSelectExpr(Walker *pWalker, Select *p){ 127 if( sqlite3WalkExprList(pWalker, p->pEList) ) return WRC_Abort; 128 if( sqlite3WalkExpr(pWalker, p->pWhere) ) return WRC_Abort; 129 if( sqlite3WalkExprList(pWalker, p->pGroupBy) ) return WRC_Abort; 130 if( sqlite3WalkExpr(pWalker, p->pHaving) ) return WRC_Abort; 131 if( sqlite3WalkExprList(pWalker, p->pOrderBy) ) return WRC_Abort; 132 if( sqlite3WalkExpr(pWalker, p->pLimit) ) return WRC_Abort; 133 #if !defined(SQLITE_OMIT_WINDOWFUNC) && !defined(SQLITE_OMIT_ALTERTABLE) 134 { 135 Parse *pParse = pWalker->pParse; 136 if( pParse && IN_RENAME_OBJECT ){ 137 /* The following may return WRC_Abort if there are unresolvable 138 ** symbols (e.g. a table that does not exist) in a window definition. */ 139 int rc = walkWindowList(pWalker, p->pWinDefn, 0); 140 return rc; 141 } 142 } 143 #endif 144 return WRC_Continue; 145 } 146 147 /* 148 ** Walk the parse trees associated with all subqueries in the 149 ** FROM clause of SELECT statement p. Do not invoke the select 150 ** callback on p, but do invoke it on each FROM clause subquery 151 ** and on any subqueries further down in the tree. Return 152 ** WRC_Abort or WRC_Continue; 153 */ 154 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){ 155 SrcList *pSrc; 156 int i; 157 SrcItem *pItem; 158 159 pSrc = p->pSrc; 160 if( pSrc ){ 161 for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){ 162 if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){ 163 return WRC_Abort; 164 } 165 if( pItem->fg.isTabFunc 166 && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg) 167 ){ 168 return WRC_Abort; 169 } 170 } 171 } 172 return WRC_Continue; 173 } 174 175 /* 176 ** Call sqlite3WalkExpr() for every expression in Select statement p. 177 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and 178 ** on the compound select chain, p->pPrior. 179 ** 180 ** If it is not NULL, the xSelectCallback() callback is invoked before 181 ** the walk of the expressions and FROM clause. The xSelectCallback2() 182 ** method is invoked following the walk of the expressions and FROM clause, 183 ** but only if both xSelectCallback and xSelectCallback2 are both non-NULL 184 ** and if the expressions and FROM clause both return WRC_Continue; 185 ** 186 ** Return WRC_Continue under normal conditions. Return WRC_Abort if 187 ** there is an abort request. 188 ** 189 ** If the Walker does not have an xSelectCallback() then this routine 190 ** is a no-op returning WRC_Continue. 191 */ 192 int sqlite3WalkSelect(Walker *pWalker, Select *p){ 193 int rc; 194 if( p==0 ) return WRC_Continue; 195 if( pWalker->xSelectCallback==0 ) return WRC_Continue; 196 do{ 197 rc = pWalker->xSelectCallback(pWalker, p); 198 if( rc ) return rc & WRC_Abort; 199 if( sqlite3WalkSelectExpr(pWalker, p) 200 || sqlite3WalkSelectFrom(pWalker, p) 201 ){ 202 return WRC_Abort; 203 } 204 if( pWalker->xSelectCallback2 ){ 205 pWalker->xSelectCallback2(pWalker, p); 206 } 207 p = p->pPrior; 208 }while( p!=0 ); 209 return WRC_Continue; 210 } 211 212 /* Increase the walkerDepth when entering a subquery, and 213 ** descrease when leaving the subquery. 214 */ 215 int sqlite3WalkerDepthIncrease(Walker *pWalker, Select *pSelect){ 216 UNUSED_PARAMETER(pSelect); 217 pWalker->walkerDepth++; 218 return WRC_Continue; 219 } 220 void sqlite3WalkerDepthDecrease(Walker *pWalker, Select *pSelect){ 221 UNUSED_PARAMETER(pSelect); 222 pWalker->walkerDepth--; 223 } 224 225 226 /* 227 ** No-op routine for the parse-tree walker. 228 ** 229 ** When this routine is the Walker.xExprCallback then expression trees 230 ** are walked without any actions being taken at each node. Presumably, 231 ** when this routine is used for Walker.xExprCallback then 232 ** Walker.xSelectCallback is set to do something useful for every 233 ** subquery in the parser tree. 234 */ 235 int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){ 236 UNUSED_PARAMETER2(NotUsed, NotUsed2); 237 return WRC_Continue; 238 } 239 240 /* 241 ** No-op routine for the parse-tree walker for SELECT statements. 242 ** subquery in the parser tree. 243 */ 244 int sqlite3SelectWalkNoop(Walker *NotUsed, Select *NotUsed2){ 245 UNUSED_PARAMETER2(NotUsed, NotUsed2); 246 return WRC_Continue; 247 } 248