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Overview
Comment:Improvements to the iIdxNoSeek optimization of sqlite3GenerateRowDelete() so that it is automatically disabled for BEFORE triggers but works in all other cases.
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SHA1: 3178ec4c27efc4ff84bcd17ddb17ec50a6ac96b3
User & Date: drh 2017-01-07 14:47:03.531
Context
2017-01-09
13:43
Add the SQLITE_UINT64_TYPE compile-time option. (check-in: a5fe03bc41 user: drh tags: trunk)
2017-01-07
14:47
Improvements to the iIdxNoSeek optimization of sqlite3GenerateRowDelete() so that it is automatically disabled for BEFORE triggers but works in all other cases. (check-in: 3178ec4c27 user: drh tags: trunk)
14:26
Critical fix to the previous check-in so that it works when there are BEFORE triggers that move the cursor before the OP_Delete has a chance to be applied. (check-in: db2c0960ff user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/delete.c.
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      if( eOnePass==ONEPASS_SINGLE && sqlite3IsToplevel(pParse) ){
        pParse->isMultiWrite = 0;
      }
    }else
#endif
    {
      int count = (pParse->nested==0);    /* True to count changes */
      int iIdxNoSeek = bComplex ? -1 : aiCurOnePass[1];
      sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
          iKey, nKey, count, OE_Default, eOnePass, iIdxNoSeek);
    }
  
    /* End of the loop over all rowids/primary-keys. */
    if( eOnePass!=ONEPASS_OFF ){
      sqlite3VdbeResolveLabel(v, addrBypass);
      sqlite3WhereEnd(pWInfo);
    }else if( pPk ){







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      if( eOnePass==ONEPASS_SINGLE && sqlite3IsToplevel(pParse) ){
        pParse->isMultiWrite = 0;
      }
    }else
#endif
    {
      int count = (pParse->nested==0);    /* True to count changes */

      sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
          iKey, nKey, count, OE_Default, eOnePass, aiCurOnePass[1]);
    }
  
    /* End of the loop over all rowids/primary-keys. */
    if( eOnePass!=ONEPASS_OFF ){
      sqlite3VdbeResolveLabel(v, addrBypass);
      sqlite3WhereEnd(pWInfo);
    }else if( pPk ){
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**   operation. Or, if iIdxNoSeek is not a valid cursor number, the
**   position of iDataCur should be preserved instead.
**
** iIdxNoSeek:
**   If iIdxNoSeek is a valid cursor number (>=0) not equal to iDataCur,
**   then it identifies an index cursor (from within array of cursors
**   starting at iIdxCur) that already points to the index entry to be deleted.


*/
void sqlite3GenerateRowDelete(
  Parse *pParse,     /* Parsing context */
  Table *pTab,       /* Table containing the row to be deleted */
  Trigger *pTrigger, /* List of triggers to (potentially) fire */
  int iDataCur,      /* Cursor from which column data is extracted */
  int iIdxCur,       /* First index cursor */







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**   operation. Or, if iIdxNoSeek is not a valid cursor number, the
**   position of iDataCur should be preserved instead.
**
** iIdxNoSeek:
**   If iIdxNoSeek is a valid cursor number (>=0) not equal to iDataCur,
**   then it identifies an index cursor (from within array of cursors
**   starting at iIdxCur) that already points to the index entry to be deleted.
**   Except, this optimization is disabled if there are BEFORE triggers since
**   the trigger body might have moved the cursor.
*/
void sqlite3GenerateRowDelete(
  Parse *pParse,     /* Parsing context */
  Table *pTab,       /* Table containing the row to be deleted */
  Trigger *pTrigger, /* List of triggers to (potentially) fire */
  int iDataCur,      /* Cursor from which column data is extracted */
  int iIdxCur,       /* First index cursor */
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        TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel
    );

    /* If any BEFORE triggers were coded, then seek the cursor to the 
    ** row to be deleted again. It may be that the BEFORE triggers moved
    ** the cursor or already deleted the row that the cursor was
    ** pointing to.



    */
    if( addrStart<sqlite3VdbeCurrentAddr(v) ){
      sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);
      VdbeCoverageIf(v, opSeek==OP_NotExists);
      VdbeCoverageIf(v, opSeek==OP_NotFound);


    }

    /* Do FK processing. This call checks that any FK constraints that
    ** refer to this table (i.e. constraints attached to other tables) 
    ** are not violated by deleting this row.  */
    sqlite3FkCheck(pParse, pTab, iOld, 0, 0, 0);
  }







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        TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel
    );

    /* If any BEFORE triggers were coded, then seek the cursor to the 
    ** row to be deleted again. It may be that the BEFORE triggers moved
    ** the cursor or already deleted the row that the cursor was
    ** pointing to.
    **
    ** Also disable the iIdxNoSeek optimization since the BEFORE trigger
    ** may have moved that cursor.
    */
    if( addrStart<sqlite3VdbeCurrentAddr(v) ){
      sqlite3VdbeAddOp4Int(v, opSeek, iDataCur, iLabel, iPk, nPk);
      VdbeCoverageIf(v, opSeek==OP_NotExists);
      VdbeCoverageIf(v, opSeek==OP_NotFound);
      testcase( iIdxNoSeek>=0 );
      iIdxNoSeek = -1;
    }

    /* Do FK processing. This call checks that any FK constraints that
    ** refer to this table (i.e. constraints attached to other tables) 
    ** are not violated by deleting this row.  */
    sqlite3FkCheck(pParse, pTab, iOld, 0, 0, 0);
  }
Changes to src/insert.c.
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        assert( onError==OE_Replace );
        sqlite3MultiWrite(pParse);
        if( db->flags&SQLITE_RecTriggers ){
          pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
        }
        sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
            regR, nPkField, 0, OE_Replace,
            (pIdx==pPk ? ONEPASS_SINGLE : ONEPASS_OFF),
            (pTrigger ? -1 : iThisCur));
        seenReplace = 1;
        break;
      }
    }
    sqlite3VdbeResolveLabel(v, addrUniqueOk);
    if( regR!=regIdx ) sqlite3ReleaseTempRange(pParse, regR, nPkField);
  }







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        assert( onError==OE_Replace );
        sqlite3MultiWrite(pParse);
        if( db->flags&SQLITE_RecTriggers ){
          pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
        }
        sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
            regR, nPkField, 0, OE_Replace,
            (pIdx==pPk ? ONEPASS_SINGLE : ONEPASS_OFF), iThisCur);

        seenReplace = 1;
        break;
      }
    }
    sqlite3VdbeResolveLabel(v, addrUniqueOk);
    if( regR!=regIdx ) sqlite3ReleaseTempRange(pParse, regR, nPkField);
  }