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Overview
Comment:Initial implementation of an optimization that attempts to reuse the same materialization of a view on a self-join of the view.
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SHA3-256:478c34b9a8b5127d13024e10307aa832f160b89720c46424dd17555bd36f590d
User & Date: drh 2017-05-01 15:15:41
Context
2017-05-01
16:37
Minor bug fixes and performance enhancement. check-in: b2aae559 user: drh tags: materialized-view-reuse
15:15
Initial implementation of an optimization that attempts to reuse the same materialization of a view on a self-join of the view. check-in: 478c34b9 user: drh tags: materialized-view-reuse
2017-04-29
19:29
Add a single testcase() macro to the subquery processing logic. check-in: 4e1df76e user: drh tags: trunk
Changes
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Changes to src/select.c.

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        pParse->pVdbe, OP_Explain, pParse->iSelectId, 0, 0, zEqp, P4_DYNAMIC
    );
  }
}
#else
# define explainSimpleCount(a,b,c)
#endif



















/*
** Generate code for the SELECT statement given in the p argument.  
**
** The results are returned according to the SelectDest structure.
** See comments in sqliteInt.h for further information.
**
................................................................................
      ** the content of this subquery.  pItem->addrFillSub will point
      ** to the address of the generated subroutine.  pItem->regReturn
      ** is a register allocated to hold the subroutine return address
      */
      int topAddr;
      int onceAddr = 0;
      int retAddr;


      assert( pItem->addrFillSub==0 );
      pItem->regReturn = ++pParse->nMem;
      topAddr = sqlite3VdbeAddOp2(v, OP_Integer, 0, pItem->regReturn);
      pItem->addrFillSub = topAddr+1;
      if( pItem->fg.isCorrelated==0 ){
        /* If the subquery is not correlated and if we are not inside of
        ** a trigger, then we only need to compute the value of the subquery
        ** once. */
        onceAddr = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
        VdbeComment((v, "materialize \"%s\"", pItem->pTab->zName));
      }else{
        VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
      }




      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);
      VdbeComment((v, "end %s", pItem->pTab->zName));
      sqlite3VdbeChangeP1(v, topAddr, retAddr);
      sqlite3ClearTempRegCache(pParse);
    }







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        pParse->pVdbe, OP_Explain, pParse->iSelectId, 0, 0, zEqp, P4_DYNAMIC
    );
  }
}
#else
# 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.  
**
** The results are returned according to the SelectDest structure.
** See comments in sqliteInt.h for further information.
**
................................................................................
      ** the content of this subquery.  pItem->addrFillSub will point
      ** to the address of the generated subroutine.  pItem->regReturn
      ** is a register allocated to hold the subroutine return address
      */
      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);
      pItem->addrFillSub = topAddr+1;
      if( pItem->fg.isCorrelated==0 ){
        /* If the subquery is not correlated and if we are not inside of
        ** a trigger, then we only need to compute the value of the subquery
        ** once. */
        onceAddr = sqlite3VdbeAddOp0(v, OP_Once); VdbeCoverage(v);
        VdbeComment((v, "materialize \"%s\"", pItem->pTab->zName));
      }else{
        VdbeNoopComment((v, "materialize \"%s\"", pItem->pTab->zName));
      }
      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);
      VdbeComment((v, "end %s", pItem->pTab->zName));
      sqlite3VdbeChangeP1(v, topAddr, retAddr);
      sqlite3ClearTempRegCache(pParse);
    }

Changes to src/vdbe.c.

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  testcase( pOp->p2 & OPFLAG_SEEKEQ );
#endif
  sqlite3BtreeCursorHintFlags(pCur->uc.pCursor,
                               (pOp->p5 & (OPFLAG_BULKCSR|OPFLAG_SEEKEQ)));
  if( rc ) goto abort_due_to_error;
  break;
}





























/* Opcode: OpenEphemeral P1 P2 * P4 P5
** Synopsis: nColumn=P2
**
** Open a new cursor P1 to a transient table.
** The cursor is always opened read/write even if 
** the main database is read-only.  The ephemeral







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  testcase( pOp->p2 & OPFLAG_SEEKEQ );
#endif
  sqlite3BtreeCursorHintFlags(pCur->uc.pCursor,
                               (pOp->p5 & (OPFLAG_BULKCSR|OPFLAG_SEEKEQ)));
  if( rc ) goto abort_due_to_error;
  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
**
** Open a new cursor P1 to a transient table.
** The cursor is always opened read/write even if 
** the main database is read-only.  The ephemeral

Changes to src/vdbeaux.c.

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      break;
    }
    case CURTYPE_BTREE: {
      if( pCx->pBtx ){
        sqlite3BtreeClose(pCx->pBtx);
        /* The pCx->pCursor will be close automatically, if it exists, by
        ** the call above. */
      }else{
        assert( pCx->uc.pCursor!=0 );
        sqlite3BtreeCloseCursor(pCx->uc.pCursor);
      }
      break;
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    case CURTYPE_VTAB: {







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      break;
    }
    case CURTYPE_BTREE: {
      if( pCx->pBtx ){
        sqlite3BtreeClose(pCx->pBtx);
        /* The pCx->pCursor will be close automatically, if it exists, by
        ** the call above. */
      }else if( !pCx->isEphemeral ){
        assert( pCx->uc.pCursor!=0 );
        sqlite3BtreeCloseCursor(pCx->uc.pCursor);
      }
      break;
    }
#ifndef SQLITE_OMIT_VIRTUALTABLE
    case CURTYPE_VTAB: {