Reuse the same materialization of a view when that view appears in a query

more than once, such as in a self-join.

FossilOrigin-Name: 9e35c89dbe744312f612e507b51ff9a5bb656def75392d25bc19fc638548cd1e

manifest

@@ -1,5 +1,5 @@
-C Move\sterms\sof\sthe\sHAVING\sclause\sthat\sreference\sonly\scolumns\sin\sthe\sGROUP\sBY\nclause\sover\sto\sthe\sWHERE\sclause,\sresulting\sin\sa\sfaster\squery\splan.
-D 2017-05-02T16:55:07.827
+C Reuse\sthe\ssame\smaterialization\sof\sa\sview\swhen\sthat\sview\sappears\sin\sa\squery\nmore\sthan\sonce,\ssuch\sas\sin\sa\sself-join.
+D 2017-05-02T17:54:19.760
 F Makefile.in 1cc758ce3374a32425e4d130c2fe7b026b20de5b8843243de75f087c0a2661fb
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 6a8c838220f7c00820e1fc0ac1bccaaa8e5676067e1dbfa1bafa7a4ffecf8ae6
@@ -402,7 +402,7 @@ F src/printf.c 8757834f1b54dae512fb25eb1acc8e94a0d15dd2290b58f2563f65973265adb2
 F src/random.c 80f5d666f23feb3e6665a6ce04c7197212a88384
 F src/resolve.c 3e518b962d932a997fae373366880fc028c75706
 F src/rowset.c 7b7e7e479212e65b723bf40128c7b36dc5afdfac
-F src/select.c 4bbdacd119f22b3b7712b1c1f54bb52fdc7d97d24e131440cc5f235b9df42b0c
+F src/select.c 4f0adefaa5e9417459b07757e0f6060cac97930a86f0fba9797bab233ced66c0
 F src/shell.c 21b79c0e1b93f8e35fd7b4087d6ba438326c3d7e285d0dd51dfd741475f858a1
 F src/sqlite.h.in eeb1da70a61d52e1d58e5b55446b85bbac571699421d3cf857421c56214013ce
 F src/sqlite3.rc 5121c9e10c3964d5755191c80dd1180c122fc3a8
@@ -469,11 +469,11 @@ F src/update.c c443935c652af9365e033f756550b5032d02e1b06eb2cb890ed7511ae0c051dc
 F src/utf.c 699001c79f28e48e9bcdf8a463da029ea660540c
 F src/util.c ca8440ede81e155d15cff7c101654f60b55a9ae6
 F src/vacuum.c 1fe4555cd8c9b263afb85b5b4ee3a4a4181ad569
-F src/vdbe.c 349eb6789cf8b03ef1aa42271aa9a17a6a7794c07448d27c5405904ba1b21715
+F src/vdbe.c 9bac2bc2313ed682e6f48ccff6644d3263341885bfcbb3cdea7b720c722be2d5
 F src/vdbe.h f7d1456e28875c2dcb964056589b5b7149ab7edf39edeca801596a39bb3d3848
 F src/vdbeInt.h c070bc5c8b913bda0ceaa995cd4d939ded5e4fc96cf7c3c1c602d41b871f8ade
 F src/vdbeapi.c 5b08d82592bcff4470601fe78aaabebd50837860
-F src/vdbeaux.c 6b3f6ce909e206d4c918988b13b7fa687e92b4471d137e0f2a37edac80ec60be
+F src/vdbeaux.c b4999c744e59deba7ab8733640219ecbc771721b362d7e26ce4c57db575ad80b
 F src/vdbeblob.c 359891617358deefc85bef7bcf787fa6b77facb9
 F src/vdbemem.c 2c70f8f5de6c71fb99a22c5b83be9fab5c47cdd8e279fa44a8c00cfed06d7e89
 F src/vdbesort.c e72fe02a2121386ba767ede8942e9450878b8fc873abf3d1b6824485f092570c
@@ -1578,8 +1578,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 6674814afb9e763e7f7060776586e26da28040b3208ce06c8a285dd647e5a53d 8424492eac506866d2918e5fe03c8f65fef960215d56012a3b52ed42789ed35a
-R 645ee5368137c061c8ff554b7c3cb973
-T +closed 8424492eac506866d2918e5fe03c8f65fef960215d56012a3b52ed42789ed35a
+P 47cbb471d056c8e1834a5ca72491404a3bfb273b5ff7bdd84b98d263938ea874 c64fe3a1695925693385d313e9ad2a1d8cb37ddaa8cc19920ae0978c91bc4c2c
+R 250cb39f933147d7683c248b1fcd12aa
+T +closed c64fe3a1695925693385d313e9ad2a1d8cb37ddaa8cc19920ae0978c91bc4c2c
 U drh
-Z f125bc7c2e400862ed032d286e9e90a2
+Z d1eca8aa444c2ea7562fa3a6e3e0ab31

manifest.uuid

@@ -1 +1 @@
-47cbb471d056c8e1834a5ca72491404a3bfb273b5ff7bdd84b98d263938ea874
+9e35c89dbe744312f612e507b51ff9a5bb656def75392d25bc19fc638548cd1e

src/select.c

@@ -4950,6 +4950,32 @@ static void havingToWhere(
   sqlite3WalkExpr(&sWalker, pHaving);
 }
 
+/*
+** Check to see if the pThis entry of pTabList is a self-join of a prior view.
+** If it is, then return the SrcList_item for the prior view.  If it is not,
+** then return 0.
+*/
+static struct SrcList_item *isSelfJoinView(
+  SrcList *pTabList,           /* Search for self-joins in this FROM clause */
+  struct SrcList_item *pThis   /* Search for prior reference to this subquery */
+){
+  struct SrcList_item *pItem;
+  for(pItem = pTabList->a; pItem<pThis; pItem++){
+    if( pItem->pSelect==0 ) continue;
+    if( pItem->fg.viaCoroutine ) continue;
+    if( pItem->zName==0 ) continue;
+    if( sqlite3_stricmp(pItem->zDatabase, pThis->zDatabase)!=0 ) continue;
+    if( sqlite3_stricmp(pItem->zName, pThis->zName)!=0 ) continue;
+    if( sqlite3ExprCompare(pThis->pSelect->pWhere, pItem->pSelect->pWhere, -1) ){
+      /* The view was modified by some other optimization such as
+      ** pushDownWhereTerms() */
+      continue;
+    }
+    return pItem;
+  }
+  return 0;
+}
+
 /*
 ** Generate code for the SELECT statement given in the p argument.  
 **
@@ -5184,6 +5210,8 @@ int sqlite3Select(
       int topAddr;
       int onceAddr = 0;
       int retAddr;
+      struct SrcList_item *pPrior;
+
       assert( pItem->addrFillSub==0 );
       pItem->regReturn = ++pParse->nMem;
       topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
@@ -5197,9 +5225,14 @@ int sqlite3Select(
       }else{
         VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
       }
-      sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
-      explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
-      sqlite3Select(pParse, pSub, &dest);
+      pPrior = isSelfJoinView(pTabList, pItem);
+      if( pPrior ){
+        sqlite3VdbeAddOp2(v, OP_OpenDup, pItem->iCursor, pPrior->iCursor);
+      }else{
+        sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
+        explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
+        sqlite3Select(pParse, pSub, &dest);
+      }
       pItem->pTab->nRowLogEst = pSub->nSelectRow;
       if( onceAddr ) sqlite3VdbeJumpHere(v, onceAddr);
       retAddr = sqlite3VdbeAddOp1(v, OP_Return, pItem->regReturn);

src/vdbe.c

@@ -3540,6 +3540,37 @@ open_cursor_set_hints:
   break;
 }
 
+/* Opcode: OpenDup P1 P2 * * *
+**
+** Open a new cursor P1 that points to the same ephemeral table as
+** cursor P2.  The P2 cursor must have been opened by a prior OP_OpenEphemeral
+** opcode.  Only ephemeral cursors may be duplicated.
+**
+** Duplicate ephemeral cursors are used for self-joins of materialized views.
+*/
+case OP_OpenDup: {
+  VdbeCursor *pOrig;    /* The original cursor to be duplicated */
+  VdbeCursor *pCx;      /* The new cursor */
+
+  pOrig = p->apCsr[pOp->p2];
+  assert( pOrig->pBtx!=0 );  /* Only ephemeral cursors can be duplicated */
+
+  pCx = allocateCursor(p, pOp->p1, pOrig->nField, -1, CURTYPE_BTREE);
+  if( pCx==0 ) goto no_mem;
+  pCx->nullRow = 1;
+  pCx->isEphemeral = 1;
+  pCx->pKeyInfo = pOrig->pKeyInfo;
+  pCx->isTable = pOrig->isTable;
+  rc = sqlite3BtreeCursor(pOrig->pBtx, MASTER_ROOT, BTREE_WRCSR,
+                          pCx->pKeyInfo, pCx->uc.pCursor);
+  /* The sqlite3BtreeCursor() routine can only fail for the first cursor
+  ** opened for a database.  Since there is already an open cursor when this
+  ** opcode is run, the sqlite3BtreeCursor() cannot fail */
+  assert( rc==SQLITE_OK );
+  break;
+}
+
+
 /* Opcode: OpenEphemeral P1 P2 * P4 P5
 ** Synopsis: nColumn=P2
 **

src/vdbeaux.c

@@ -2035,8 +2035,8 @@ void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
       break;
     }
     case CURTYPE_BTREE: {
-      if( pCx->pBtx ){
-        sqlite3BtreeClose(pCx->pBtx);
+      if( pCx->isEphemeral ){
+        if( pCx->pBtx ) sqlite3BtreeClose(pCx->pBtx);
         /* The pCx->pCursor will be close automatically, if it exists, by
         ** the call above. */
       }else{