Initial implementation of an optimization that attempts to reuse the same

materialization of a view on a self-join of the view.

FossilOrigin-Name: 478c34b9a8b5127d13024e10307aa832f160b89720c46424dd17555bd36f590d

manifest

@@ -1,5 +1,5 @@
-C Add\sa\ssingle\stestcase()\smacro\sto\sthe\ssubquery\sprocessing\slogic.
+C Initial\simplementation\sof\san\soptimization\sthat\sattempts\sto\sreuse\sthe\ssame\nmaterialization\sof\sa\sview\son\sa\sself-join\sof\sthe\sview.
-D 2017-04-29T19:29:49.700
+D 2017-05-01T15:15:41.259
 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 478e95d424bb86d34c7c95d20872cbd78df97af5f83c3fd7de55d5b2413f927d
+F src/select.c 1fba56aa7d6530a37e173e5144df92ad6140c472f9807c168a2ebff096b590c7
 F src/shell.c 21b79c0e1b93f8e35fd7b4087d6ba438326c3d7e285d0dd51dfd741475f858a1
 F src/sqlite.h.in 40233103e3e4e10f8a63523498d0259d232e42aba478e2d3fb914799185aced6
 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 7c37c36f3d528b10e5a5df76267ca42ed604fb3f15ff1d656afe1f33ff5d1f76
 F src/vdbe.h f7d1456e28875c2dcb964056589b5b7149ab7edf39edeca801596a39bb3d3848
 F src/vdbeInt.h c070bc5c8b913bda0ceaa995cd4d939ded5e4fc96cf7c3c1c602d41b871f8ade
 F src/vdbeapi.c 5b08d82592bcff4470601fe78aaabebd50837860
-F src/vdbeaux.c 6b3f6ce909e206d4c918988b13b7fa687e92b4471d137e0f2a37edac80ec60be
+F src/vdbeaux.c bb99698cfee2d2fd9fa2870f8a24153475793b9c85cb626b412d6bad8c3a73a8
 F src/vdbeblob.c 359891617358deefc85bef7bcf787fa6b77facb9
 F src/vdbemem.c 2c70f8f5de6c71fb99a22c5b83be9fab5c47cdd8e279fa44a8c00cfed06d7e89
 F src/vdbesort.c e72fe02a2121386ba767ede8942e9450878b8fc873abf3d1b6824485f092570c
@@ -1577,7 +1577,10 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e54c9f8db5b2fa8ea82c6eab7482255431af16901f7992c9667b56a0e50a9f4f
+P 4e1df76e3d85922648e0e1cce73a266c3b1ed4511ace259ec0a01d7693af9e6f
-R 6f21ea13ed166571d20351d2145d6640
+R 9a92f7b5439fceb732be32bb3fe5b30d
+T *branch * materialized-view-reuse
+T *sym-materialized-view-reuse *
+T -sym-trunk *
 U drh
-Z 4a7e86f7be3de966a53a14c1a17e31d5
+Z 0a08980cdb3c200bc98cb9ecc97a5f40

manifest.uuid

@@ -1 +1 @@
-4e1df76e3d85922648e0e1cce73a266c3b1ed4511ace259ec0a01d7693af9e6f
+478c34b9a8b5127d13024e10307aa832f160b89720c46424dd17555bd36f590d

src/select.c

@@ -4879,6 +4879,24 @@ static void explainSimpleCount(
 # define explainSimpleCount(a,b,c)
 #endif
 
+/*
+** 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( sqlite3StrICmp(pItem->zName, pThis->zName)==0 ) return pItem;
+  }
+  return 0;
+}
+
 /*
 ** Generate code for the SELECT statement given in the p argument.  
 **
@@ -5113,6 +5131,8 @@ 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);
@@ -5126,9 +5146,14 @@ int sqlite3Select(
       }else{
         VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
       }
-      sqlite3SelectDestInit(&dest, SRT_EphemTab, pItem->iCursor);
+      pPrior = isSelfJoinView(pTabList, pItem);
-      explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
+      if( pPrior ){
-      sqlite3Select(pParse, pSub, &dest);
+        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 +3540,34 @@ 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);
+  if( rc ) goto abort_due_to_error;
+  break;
+}
+
+
 /* Opcode: OpenEphemeral P1 P2 * P4 P5
 ** Synopsis: nColumn=P2
 **

src/vdbeaux.c

@@ -2039,7 +2039,7 @@ void sqlite3VdbeFreeCursor(Vdbe *p, VdbeCursor *pCx){
         sqlite3BtreeClose(pCx->pBtx);
         /* The pCx->pCursor will be close automatically, if it exists, by
         ** the call above. */
-      }else{
+      }else if( !pCx->isEphemeral ){
         assert( pCx->uc.pCursor!=0 );
         sqlite3BtreeCloseCursor(pCx->uc.pCursor);
       }