src/walker.c

   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( ExprUseXSelect(pExpr) ){
  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 #ifndef SQLITE_OMIT_CTE
 144      || pWalker->xSelectCallback2==sqlite3SelectPopWith
 145 #endif
 146     ){
 147       /* The following may return WRC_Abort if there are unresolvable
 148       ** symbols (e.g. a table that does not exist) in a window definition. */
 149       int rc = walkWindowList(pWalker, p->pWinDefn, 0);
 150       return rc;
 151     }
 152   }
 153 #endif
 154   return WRC_Continue;
 155 }
 156
 157 /*
 158 ** Walk the parse trees associated with all subqueries in the
 159 ** FROM clause of SELECT statement p.  Do not invoke the select
 160 ** callback on p, but do invoke it on each FROM clause subquery
 161 ** and on any subqueries further down in the tree.  Return
 162 ** WRC_Abort or WRC_Continue;
 163 */
 164 int sqlite3WalkSelectFrom(Walker *pWalker, Select *p){
 165   SrcList *pSrc;
 166   int i;
 167   SrcItem *pItem;
 168
 169   pSrc = p->pSrc;
 170   if( ALWAYS(pSrc) ){
 171     for(i=pSrc->nSrc, pItem=pSrc->a; i>0; i--, pItem++){
 172       if( pItem->pSelect && sqlite3WalkSelect(pWalker, pItem->pSelect) ){
 173         return WRC_Abort;
 174       }
 175       if( pItem->fg.isTabFunc
 176        && sqlite3WalkExprList(pWalker, pItem->u1.pFuncArg)
 177       ){
 178         return WRC_Abort;
 179       }
 180     }
 181   }
 182   return WRC_Continue;
 183 }
 184
 185 /*
 186 ** Call sqlite3WalkExpr() for every expression in Select statement p.
 187 ** Invoke sqlite3WalkSelect() for subqueries in the FROM clause and
 188 ** on the compound select chain, p->pPrior.
 189 **
 190 ** If it is not NULL, the xSelectCallback() callback is invoked before
 191 ** the walk of the expressions and FROM clause. The xSelectCallback2()
 192 ** method is invoked following the walk of the expressions and FROM clause,
 193 ** but only if both xSelectCallback and xSelectCallback2 are both non-NULL
 194 ** and if the expressions and FROM clause both return WRC_Continue;
 195 **
 196 ** Return WRC_Continue under normal conditions.  Return WRC_Abort if
 197 ** there is an abort request.
 198 **
 199 ** If the Walker does not have an xSelectCallback() then this routine
 200 ** is a no-op returning WRC_Continue.
 201 */
 202 int sqlite3WalkSelect(Walker *pWalker, Select *p){
 203   int rc;
 204   if( p==0 ) return WRC_Continue;
 205   if( pWalker->xSelectCallback==0 ) return WRC_Continue;
 206   do{
 207     rc = pWalker->xSelectCallback(pWalker, p);
 208     if( rc ) return rc & WRC_Abort;
 209     if( sqlite3WalkSelectExpr(pWalker, p)
 210      || sqlite3WalkSelectFrom(pWalker, p)
 211     ){
 212       return WRC_Abort;
 213     }
 214     if( pWalker->xSelectCallback2 ){
 215       pWalker->xSelectCallback2(pWalker, p);
 216     }
 217     p = p->pPrior;
 218   }while( p!=0 );
 219   return WRC_Continue;
 220 }
 221
 222 /* Increase the walkerDepth when entering a subquery, and
 223 ** descrease when leaving the subquery.
 224 */
 225 int sqlite3WalkerDepthIncrease(Walker *pWalker, Select *pSelect){
 226   UNUSED_PARAMETER(pSelect);
 227   pWalker->walkerDepth++;
 228   return WRC_Continue;
 229 }
 230 void sqlite3WalkerDepthDecrease(Walker *pWalker, Select *pSelect){
 231   UNUSED_PARAMETER(pSelect);
 232   pWalker->walkerDepth--;
 233 }
 234
 235
 236 /*
 237 ** No-op routine for the parse-tree walker.
 238 **
 239 ** When this routine is the Walker.xExprCallback then expression trees
 240 ** are walked without any actions being taken at each node.  Presumably,
 241 ** when this routine is used for Walker.xExprCallback then
 242 ** Walker.xSelectCallback is set to do something useful for every
 243 ** subquery in the parser tree.
 244 */
 245 int sqlite3ExprWalkNoop(Walker *NotUsed, Expr *NotUsed2){
 246   UNUSED_PARAMETER2(NotUsed, NotUsed2);
 247   return WRC_Continue;
 248 }
 249
 250 /*
 251 ** No-op routine for the parse-tree walker for SELECT statements.
 252 ** subquery in the parser tree.
 253 */
 254 int sqlite3SelectWalkNoop(Walker *NotUsed, Select *NotUsed2){
 255   UNUSED_PARAMETER2(NotUsed, NotUsed2);
 256   return WRC_Continue;
 257 }