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Overview
Comment:Small changes to the OP_OpenEphemeral opcode to improve testability.
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SHA3-256: f856676c8438dbf52d299e78f6dd6148d929755dc05cdcabafd17d9a86439435
User & Date: drh 2018-12-31 17:58:05
Context
2018-12-31
20:39
Additional steps to help ensure that scalar subqueries are only evaluated once even if they are used in multiple places within the query. This fixes a performance regression reported on the mailing list and caused by check-in [531eca6104e41e43] which was a fix for ticket [787fa716be3a7f650c]. Think of this check-in as an improved fix for that ticket. check-in: e1303193 user: drh tags: trunk
18:30
Merge enhancements and bug fixes from trunk. check-in: 9fb646f2 user: drh tags: reuse-subqueries
17:58
Small changes to the OP_OpenEphemeral opcode to improve testability. check-in: f856676c user: drh tags: trunk
16:36
Fix the OP_OpenEphemeral opcode in the bytecode engine so that if it is called a second or subsequent time, it merely clears the existing table rather than creating a new one. Proposed fix for ticket [d0866b26f83e9c55e30de0821f5d]. check-in: 4678cb10 user: drh tags: trunk
Changes
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Changes to src/vdbe.c.

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  assert( pOp->p1>=0 );
  assert( pOp->p2>=0 );
  pCx = p->apCsr[pOp->p1];
  if( pCx ){
    /* If the ephermeral table is already open, erase all existing content
    ** so that the table is empty again, rather than creating a new table. */
    rc = sqlite3BtreeClearTable(pCx->pBtx, pCx->pgnoRoot, 0);
    if( rc ) goto abort_due_to_error;
    break;
  }
  pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, CURTYPE_BTREE);
  if( pCx==0 ) goto no_mem;
  pCx->nullRow = 1;
  pCx->isEphemeral = 1;
  rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBtx, 
                        BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5, vfsFlags);

  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeBeginTrans(pCx->pBtx, 1, 0);
  }
  if( rc==SQLITE_OK ){
    /* If a transient index is required, create it by calling
    ** sqlite3BtreeCreateTable() with the BTREE_BLOBKEY flag before
    ** opening it. If a transient table is required, just use the
    ** automatically created table with root-page 1 (an BLOB_INTKEY table).
    */
    if( (pCx->pKeyInfo = pKeyInfo = pOp->p4.pKeyInfo)!=0 ){
      assert( pOp->p4type==P4_KEYINFO );
      rc = sqlite3BtreeCreateTable(pCx->pBtx, (int*)&pCx->pgnoRoot,
                                   BTREE_BLOBKEY | pOp->p5); 
      if( rc==SQLITE_OK ){
        assert( pCx->pgnoRoot==MASTER_ROOT+1 );
        assert( pKeyInfo->db==db );
        assert( pKeyInfo->enc==ENC(db) );
        rc = sqlite3BtreeCursor(pCx->pBtx, pCx->pgnoRoot, BTREE_WRCSR,
                                pKeyInfo, pCx->uc.pCursor);
      }
      pCx->isTable = 0;
    }else{
      pCx->pgnoRoot = MASTER_ROOT;
      rc = sqlite3BtreeCursor(pCx->pBtx, MASTER_ROOT, BTREE_WRCSR,
                              0, pCx->uc.pCursor);
      pCx->isTable = 1;
    }
  }
  if( rc ) goto abort_due_to_error;
  pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);


  break;
}

/* Opcode: SorterOpen P1 P2 P3 P4 *
**
** This opcode works like OP_OpenEphemeral except that it opens
** a transient index that is specifically designed to sort large







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  assert( pOp->p1>=0 );
  assert( pOp->p2>=0 );
  pCx = p->apCsr[pOp->p1];
  if( pCx ){
    /* If the ephermeral table is already open, erase all existing content
    ** so that the table is empty again, rather than creating a new table. */
    rc = sqlite3BtreeClearTable(pCx->pBtx, pCx->pgnoRoot, 0);
  }else{


    pCx = allocateCursor(p, pOp->p1, pOp->p2, -1, CURTYPE_BTREE);
    if( pCx==0 ) goto no_mem;
    pCx->nullRow = 1;
    pCx->isEphemeral = 1;
    rc = sqlite3BtreeOpen(db->pVfs, 0, db, &pCx->pBtx, 
                          BTREE_OMIT_JOURNAL | BTREE_SINGLE | pOp->p5,
                          vfsFlags);
    if( rc==SQLITE_OK ){
      rc = sqlite3BtreeBeginTrans(pCx->pBtx, 1, 0);
    }
    if( rc==SQLITE_OK ){
      /* If a transient index is required, create it by calling
      ** sqlite3BtreeCreateTable() with the BTREE_BLOBKEY flag before
      ** opening it. If a transient table is required, just use the
      ** automatically created table with root-page 1 (an BLOB_INTKEY table).
      */
      if( (pCx->pKeyInfo = pKeyInfo = pOp->p4.pKeyInfo)!=0 ){
        assert( pOp->p4type==P4_KEYINFO );
        rc = sqlite3BtreeCreateTable(pCx->pBtx, (int*)&pCx->pgnoRoot,
                                     BTREE_BLOBKEY | pOp->p5); 
        if( rc==SQLITE_OK ){
          assert( pCx->pgnoRoot==MASTER_ROOT+1 );
          assert( pKeyInfo->db==db );
          assert( pKeyInfo->enc==ENC(db) );
          rc = sqlite3BtreeCursor(pCx->pBtx, pCx->pgnoRoot, BTREE_WRCSR,
                                  pKeyInfo, pCx->uc.pCursor);
        }
        pCx->isTable = 0;
      }else{
        pCx->pgnoRoot = MASTER_ROOT;
        rc = sqlite3BtreeCursor(pCx->pBtx, MASTER_ROOT, BTREE_WRCSR,
                                0, pCx->uc.pCursor);
        pCx->isTable = 1;
      }
    }

    pCx->isOrdered = (pOp->p5!=BTREE_UNORDERED);
  }
  if( rc ) goto abort_due_to_error;
  break;
}

/* Opcode: SorterOpen P1 P2 P3 P4 *
**
** This opcode works like OP_OpenEphemeral except that it opens
** a transient index that is specifically designed to sort large