Allow only a single recursive reference in a recursive CTE. Also require that this reference is not part of a sub-query.

FossilOrigin-Name: a296b73360d34c9364eceb2cc09a9a92adc4abb8

7 files changed, 62 insertions, 85 deletions

diff --git a/manifest b/manifest
index 86132841c..817e0abe3 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Disable\sthe\sflattening\soptimization\sif\sthe\sparent\squery\sis\sthe\srecursive\spart\sof\sa\srecursive\sCTE\sand\sthe\ssub-query\sis\sa\scompound\squery.
-D 2014-01-16T10:58:39.954
+C Allow\sonly\sa\ssingle\srecursive\sreference\sin\sa\srecursive\sCTE.\sAlso\srequire\sthat\sthis\sreference\sis\snot\spart\sof\sa\ssub-query.
+D 2014-01-16T18:34:33.041
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 2ef13430cd359f7b361bb863504e227b25cc7f81
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -175,7 +175,7 @@ F src/complete.c dc1d136c0feee03c2f7550bafc0d29075e36deac
 F src/ctime.c 77779efbe78dd678d84bfb4fc2e87b6b6ad8dccd
 F src/date.c 593c744b2623971e45affd0bde347631bdfa4625
 F src/delete.c 91e1321021db5dc266360531b8b6550009d771ff
-F src/expr.c c09e34fa7c58995009135b81f83cb62a676ad181
+F src/expr.c e239763d8b43356fa1f46f1cf41d62a076f7f72e
 F src/fault.c 160a0c015b6c2629d3899ed2daf63d75754a32bb
 F src/fkey.c 2ab0f5384b70594468ef3ac5c7ed8ca24bfd17d5
 F src/func.c 6325ac2ec10833ccf4d5c36d323709221d37ea19
@@ -219,12 +219,12 @@ F src/printf.c 85d07756e45d7496d19439dcae3e6e9e0090f269
 F src/random.c d10c1f85b6709ca97278428fd5db5bbb9c74eece
 F src/resolve.c ae278d8ce037883323f677e78c241f64289f12ec
 F src/rowset.c 64655f1a627c9c212d9ab497899e7424a34222e0
-F src/select.c 29976d169853492a20d3201e8a83eeefa39a868f
+F src/select.c 2d2da29fd4c877646109f7d2fba26b5cc454cd37
 F src/shell.c 9f3bc02a658b8f61d2cbe60cfc482f660c1c6c48
 F src/sqlite.h.in d94a8b89522f526ba711182ee161e06f8669bcc9
 F src/sqlite3.rc 11094cc6a157a028b301a9f06b3d03089ea37c3e
 F src/sqlite3ext.h 886f5a34de171002ad46fae8c36a7d8051c190fc
-F src/sqliteInt.h 6db445ce172c249c29d8f532af64fd7051fe05dd
+F src/sqliteInt.h b30bd95081be525b32551f180cf43ccfaff9f5bc
 F src/sqliteLimit.h 164b0e6749d31e0daa1a4589a169d31c0dec7b3d
 F src/status.c 7ac05a5c7017d0b9f0b4bcd701228b784f987158
 F src/table.c 2cd62736f845d82200acfa1287e33feb3c15d62e
@@ -280,7 +280,7 @@ F src/update.c c2706a6eb232a96345c35b7e1e75a188e26812bb
 F src/utf.c 6fc6c88d50448c469c5c196acf21617a24f90269
 F src/util.c e71f19b272f05c8695cf747b4bac1732685f9e5c
 F src/vacuum.c 3728d74919d4fb1356f9e9a13e27773db60b7179
-F src/vdbe.c b06d79951a3f0da9cb41cb0aae5fdf5612f718a9
+F src/vdbe.c ccc8594e89751966022642464ec2b5c5fa7840a2
 F src/vdbe.h e6c4c610fcabad4fa80ebb1efc6822a9367e2b26
 F src/vdbeInt.h 42db251e9f863401ff847b90d5fe1614c89a6a56
 F src/vdbeapi.c ce4e68ea4842cc6081046f533d088dcf01d247ad
@@ -293,7 +293,7 @@ F src/vtab.c 21b932841e51ebd7d075e2d0ad1415dce8d2d5fd
 F src/wal.c 7dc3966ef98b74422267e7e6e46e07ff6c6eb1b4
 F src/wal.h df01efe09c5cb8c8e391ff1715cca294f89668a4
 F src/walker.c e9e593d5bb798c3e67fc3893dfe7055c9e7d8d74
-F src/where.c 27eb508c4184599a826e2ef3b4319cd28ba2c7af
+F src/where.c 369b0259fabfb22644d197736ae622f762cbaba8
 F src/whereInt.h 96a75c61f1d2b9d4a8e4bb17d89deb0cf7cba358
 F test/8_3_names.test ebbb5cd36741350040fd28b432ceadf495be25b2
 F test/aggerror.test a867e273ef9e3d7919f03ef4f0e8c0d2767944f2
@@ -1150,7 +1150,7 @@ F tool/vdbe-compress.tcl 0cf56e9263a152b84da86e75a5c0cdcdb7a47891
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh d1a6de74685f360ab718efda6265994b99bbea01
 F tool/win/sqlite.vsix 030f3eeaf2cb811a3692ab9c14d021a75ce41fff
-P 7f953b568baa3eede0b9c144be0b9bc86496341a
-R 1f82ce2970e79b42a60992cde0f0f626
+P 6bfa387e82de47ca1f40225fe28d873e29d6f481
+R d0f7d170eccd6b8c29b55960683e8b9a
 U dan
-Z da04231961fbad92750efdf2d0f0da36
+Z 617b83d8e92edcc7afd63e19b605afe5
diff --git a/manifest.uuid b/manifest.uuid
index 23deb3b81..8513fb509 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-6bfa387e82de47ca1f40225fe28d873e29d6f481
\ No newline at end of file
+a296b73360d34c9364eceb2cc09a9a92adc4abb8
\ No newline at end of file
diff --git a/src/expr.c b/src/expr.c
index 897da77ed..0614be1cf 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -1065,7 +1065,6 @@ Select *sqlite3SelectDup(sqlite3 *db, Select *p, int flags){
   pNew->addrOpenEphm[1] = -1;
   pNew->addrOpenEphm[2] = -1;
   pNew->pWith = withDup(db, p->pWith);
-  pNew->pRecurse = p->pRecurse;
   return pNew;
 }
 #else
diff --git a/src/select.c b/src/select.c
index c5fb15cd8..d70d815a2 100644
--- a/src/select.c
+++ b/src/select.c
@@ -1744,7 +1744,7 @@ static int multiSelect(
   ** the last (right-most) SELECT in the series may have an ORDER BY or LIMIT.
   */
   assert( p && p->pPrior );  /* Calling function guarantees this much */
-  assert( p->pRecurse==0 || p->op==TK_ALL || p->op==TK_UNION );
+  assert( (p->selFlags & SF_Recursive)==0 || p->op==TK_ALL || p->op==TK_UNION );
   db = pParse->db;
   pPrior = p->pPrior;
   assert( pPrior->pRightmost!=pPrior );
@@ -1794,27 +1794,36 @@ static int multiSelect(
   /* If this is a recursive query, check that there is no ORDER BY or
   ** LIMIT clause. Neither of these are supported.  */
   assert( p->pOffset==0 || p->pLimit );
-  if( p->pRecurse && (p->pOrderBy || p->pLimit) ){
+  if( (p->selFlags & SF_Recursive) && (p->pOrderBy || p->pLimit) ){
     sqlite3ErrorMsg(pParse, "%s in a recursive query is not allowed",
         p->pOrderBy ? "ORDER BY" : "LIMIT"
     );
     goto multi_select_end;
   }
 
-  if( p->pRecurse ){
+  if( p->selFlags & SF_Recursive ){
+    SrcList *pSrc = p->pSrc;
     int nCol = p->pEList->nExpr;
     int addrNext;
     int addrSwap;
     int iCont, iBreak;
-    int tmp1, tmp2;               /* Cursors used to access temporary tables */
+    int tmp1;                     /* Intermediate table */
+    int tmp2;                     /* Next intermediate table */
     int tmp3 = 0;                 /* To ensure unique results if UNION */
     int eDest = SRT_Table;
     SelectDest tmp2dest;
+    int i;
 
     iBreak = sqlite3VdbeMakeLabel(v);
     iCont = sqlite3VdbeMakeLabel(v);
 
-    tmp1 = pParse->nTab++;
+    for(i=0; ALWAYS(i<pSrc->nSrc); i++){
+      if( pSrc->a[i].isRecursive ){
+        tmp1 = pSrc->a[i].iCursor;
+        break;
+      }
+    }
+
     tmp2 = pParse->nTab++;
     if( p->op==TK_UNION ){
       eDest = SRT_DistTable;
@@ -1848,11 +1857,7 @@ static int multiSelect(
     ** SELECT is running, the contents of tmp1 are read by recursive 
     ** references to the current CTE.  */
     p->pPrior = 0;
-    p->pRecurse->tnum = tmp1;
-    assert( (p->pRecurse->tabFlags & TF_Recursive)==0 );
-    p->pRecurse->tabFlags |= TF_Recursive;
     rc = sqlite3Select(pParse, p, &tmp2dest);
-    p->pRecurse->tabFlags &= ~TF_Recursive;
     assert( p->pPrior==0 );
     p->pPrior = pPrior;
     if( rc ) goto multi_select_end;
@@ -3009,8 +3014,8 @@ static int flattenSubquery(
   if( pSub->pLimit && (p->selFlags & SF_Distinct)!=0 ){
      return 0;         /* Restriction (21) */
   }
-  if( pSub->pRecurse ) return 0;                         /* Restriction (22)  */
-  if( p->pRecurse && pSub->pPrior ) return 0;            /* Restriction (23)  */
+  if( pSub->selFlags & SF_Recursive ) return 0;          /* Restriction (22)  */
+  if( (p->selFlags & SF_Recursive) && pSub->pPrior ) return 0;       /* (23)  */
 
   /* OBSOLETE COMMENT 1:
   ** Restriction 3:  If the subquery is a join, make sure the subquery is 
@@ -3593,19 +3598,10 @@ static int withExpand(
   assert( pFrom->pTab==0 );
 
   pCte = searchWith(pParse->pWith, pFrom);
-  if( pCte==0 ){
-    /* no-op */
-  }else if( pCte==pParse->pCte && (pTab = pCte->pTab) ){
-    /* This is the recursive part of a recursive CTE */
-    assert( pFrom->pTab==0 && pFrom->isRecursive==0 && pFrom->pSelect==0 );
-    pFrom->pTab = pTab;
-    pFrom->isRecursive = 1;
-    pTab->nRef++;
-  }else{
+  if( pCte ){
     ExprList *pEList;
     Select *pSel;
     Select *pLeft;                /* Left-most SELECT statement */
-    int bRecursive;
 
     pFrom->pTab = pTab = sqlite3DbMallocZero(db, sizeof(Table));
     if( pTab==0 ) return WRC_Abort;
@@ -3618,15 +3614,36 @@ static int withExpand(
     if( db->mallocFailed ) return SQLITE_NOMEM;
     assert( pFrom->pSelect );
 
-    if( ctePush(pParse, pCte) ) return WRC_Abort;
+    /* Check if this is a recursive CTE. */
     pSel = pFrom->pSelect;
-    bRecursive = (pSel->op==TK_ALL || pSel->op==TK_UNION);
-    if( bRecursive ){
-      assert( pSel->pPrior );
-      sqlite3WalkSelect(pWalker, pSel->pPrior);
-    }else{
-      sqlite3WalkSelect(pWalker, pSel);
+    if( pSel->op==TK_ALL || pSel->op==TK_UNION ){
+      int i;
+      SrcList *pSrc = pFrom->pSelect->pSrc;
+      for(i=0; i<pSrc->nSrc; i++){
+        struct SrcList_item *pItem = &pSrc->a[i];
+        if( pItem->zDatabase==0 
+         && pItem->zName!=0 
+         && 0==sqlite3StrICmp(pItem->zName, pCte->zName)
+          ){
+          pItem->pTab = pTab;
+          pItem->isRecursive = 1;
+          pTab->nRef++;
+          pSel->selFlags |= SF_Recursive;
+        }
+      }
+    }
+
+    /* Only one recursive reference is permitted. */ 
+    if( pTab->nRef>2 ){
+      sqlite3ErrorMsg(
+          pParse, "multiple recursive references in cte: %s", pCte->zName
+      );
+      return WRC_Abort;
     }
+    assert( pTab->nRef==1 || ((pSel->selFlags&SF_Recursive) && pTab->nRef==2 ));
+
+    if( ctePush(pParse, pCte) ) return WRC_Abort;
+    sqlite3WalkSelect(pWalker, pTab->nRef==2 ? pSel->pPrior : pSel);
 
     for(pLeft=pSel; pLeft->pPrior; pLeft=pLeft->pPrior);
     pEList = pLeft->pEList;
@@ -3639,20 +3656,9 @@ static int withExpand(
       }
       pEList = pCte->pCols;
     }
-
     selectColumnsFromExprList(pParse, pEList, &pTab->nCol, &pTab->aCol);
 
-    if( bRecursive ){
-      int nRef = pTab->nRef;
-      pCte->pTab = pTab;
-      sqlite3WalkSelect(pWalker, pSel);
-      pCte->pTab = 0;
-      if( pTab->nRef > nRef){
-        pSel->pRecurse = pTab;
-        assert( pTab->tnum==0 );
-      }
-    }
-
+    if( pSel->selFlags & SF_Recursive ) sqlite3WalkSelect(pWalker, pSel);
     ctePop(pParse, pCte);
   }
 
@@ -3715,6 +3721,8 @@ static int selectExpander(Walker *pWalker, Select *p){
   */
   for(i=0, pFrom=pTabList->a; i<pTabList->nSrc; i++, pFrom++){
     Table *pTab;
+    assert( pFrom->isRecursive==0 || pFrom->pTab );
+    if( pFrom->isRecursive ) continue;
     if( pFrom->pTab!=0 ){
       /* This statement has already been prepared.  There is no need
       ** to go further. */
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 733dad2d8..43a1a57b0 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2131,7 +2131,6 @@ struct NameContext {
 */
 struct Select {
   ExprList *pEList;      /* The fields of the result */
-  Table *pRecurse;       /* Non-NULL for the recursive part of recursive CTE */
   u8 op;                 /* One of: TK_UNION TK_ALL TK_INTERSECT TK_EXCEPT */
   u16 selFlags;          /* Various SF_* values */
   int iLimit, iOffset;   /* Memory registers holding LIMIT & OFFSET counters */
@@ -2165,6 +2164,7 @@ struct Select {
 #define SF_Materialize     0x0100  /* Force materialization of views */
 #define SF_NestedFrom      0x0200  /* Part of a parenthesized FROM clause */
 #define SF_MaybeConvert    0x0400  /* Need convertCompoundSelectToSubquery() */
+#define SF_Recursive       0x0800  /* The recursive part of a recursive CTE */
 
 
 /*
@@ -2640,7 +2640,7 @@ int sqlite3WalkSelectFrom(Walker*, Select*);
 #define WRC_Abort       2   /* Abandon the tree walk */
 
 /*
-** An instance of this structure represents a set of on or more CTEs
+** An instance of this structure represents a set of one or more CTEs
 ** (common table expressions) created by a single WITH clause.
 */
 struct With {
@@ -2651,7 +2651,6 @@ struct With {
     ExprList *pCols;                /* List of explicit column names, or NULL */
     Select *pSelect;                /* The definition of this CTE */
     struct Cte *pOuterCte;          /* Next WITH clause in outer context */
-    Table *pTab;                    /* Table object for this CTE */
   } a[1];
 };
 
diff --git a/src/vdbe.c b/src/vdbe.c
index 301707677..9af4a62d7 100644
--- a/src/vdbe.c
+++ b/src/vdbe.c
@@ -3370,29 +3370,6 @@ case OP_OpenEphemeral: {
 }
 
 #ifndef SQLITE_OMIT_CTE
-/* Opcode: OpenEphreader P1 P2 * * *
-**
-** P2 is a cursor opened by the OpenEphemeral opcode. This opcode opens
-** a new read-only cursor named P1 that accesses the same epheremal table 
-** as P2.
-*/
-case OP_OpenEphreader: {
-  VdbeCursor *pEph;
-  VdbeCursor *pCx;
-  Pgno pgno;
-
-  pEph = p->apCsr[pOp->p2];
-  pCx = allocateCursor(p, pOp->p1, pEph->nField, -1, 1);
-  if( pCx==0 ) goto no_mem;
-  pCx->nullRow = 1;
-  pCx->pKeyInfo = pEph->pKeyInfo;
-  pCx->isTable = pEph->isTable;
-  pCx->isOrdered = pEph->isOrdered;
-  pgno = MASTER_ROOT + !pCx->isTable;
-  rc = sqlite3BtreeCursor(pEph->pBt, pgno, 0, pCx->pKeyInfo, pCx->pCursor);
-  break;
-}
-
 /* Opcode: SwapCursors P1 P2 * * *
 **
 ** Parameters P1 and P2 are both cursors opened by the OpenEphemeral
diff --git a/src/where.c b/src/where.c
index f1cf29b2e..52bf46a74 100644
--- a/src/where.c
+++ b/src/where.c
@@ -5654,13 +5654,7 @@ WhereInfo *sqlite3WhereBegin(
     iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
     pLoop = pLevel->pWLoop;
     if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ){
-#ifndef SQLITE_OMIT_CTE
-      if( pTab->tabFlags & TF_Recursive ){
-        int iCur = pTabItem->iCursor;
-        sqlite3VdbeAddOp2(v, OP_OpenEphreader, iCur, pTab->tnum);
-      }
-#endif
-      /* Otherwise do nothing */
+      /* Do nothing */
     }else
 #ifndef SQLITE_OMIT_VIRTUALTABLE
     if( (pLoop->wsFlags & WHERE_VIRTUALTABLE)!=0 ){