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