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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

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Overview
Comment:Optimize out a NotExists/NotFound opcode that occurs in UPDATE processing after constraint checks if there is no possiblity that the constraint checking code might have moved the cursor.
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SHA1: 74e3ee2ee6ea89af2c12dd0bce248467fd0f1310
User & Date: drh 2013-11-08 01:09:15
Context
2013-11-08
12:14
Merge change to drop the mutex on the multiplexor before entering the xRead VFS call, in order to enhance parallelizability. check-in: 3c566e41 user: drh tags: trunk
01:09
Optimize out a NotExists/NotFound opcode that occurs in UPDATE processing after constraint checks if there is no possiblity that the constraint checking code might have moved the cursor. check-in: 74e3ee2e user: drh tags: trunk
00:16
On the --summary output of wordcount, add the a PRAGMA integrity_check and a 64-bit checksum of the entire table. check-in: 1d1d13b8 user: drh tags: trunk
Changes
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Changes to src/insert.c.

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    sqlite3VdbeAddOp2(v, OP_Goto, 0, ipkTop+1);
    sqlite3VdbeJumpHere(v, ipkBottom);
  }
  
  if( pbMayReplace ){
    *pbMayReplace = seenReplace;
  }
  VdbeModuleComment((v, "END: GenCnstCks()"));
}

/*
** This routine generates code to finish the INSERT or UPDATE operation
** that was started by a prior call to sqlite3GenerateConstraintChecks.
** A consecutive range of registers starting at regNewData contains the
** rowid and the content to be inserted.







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    sqlite3VdbeAddOp2(v, OP_Goto, 0, ipkTop+1);
    sqlite3VdbeJumpHere(v, ipkBottom);
  }
  
  if( pbMayReplace ){
    *pbMayReplace = seenReplace;
  }
  VdbeModuleComment((v, "END: GenCnstCks(%d)", seenReplace));
}

/*
** This routine generates code to finish the INSERT or UPDATE operation
** that was started by a prior call to sqlite3GenerateConstraintChecks.
** A consecutive range of registers starting at regNewData contains the
** rowid and the content to be inserted.

Changes to src/update.c.

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      if( aXRef[i]<0 && i!=pTab->iPKey ){
        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, regNew+i);
      }
    }
  }

  if( !isView ){
    int j1;                       /* Address of jump instruction */


    /* Do constraint checks. */
    assert( regOldRowid>0 );
    sqlite3GenerateConstraintChecks(pParse, pTab, aRegIdx, iDataCur, iIdxCur,
        regNewRowid, regOldRowid, chngKey, onError, labelContinue, 0);

    /* Do FK constraint checks. */
    if( hasFK ){
      sqlite3FkCheck(pParse, pTab, regOldRowid, 0, aXRef, chngKey);
    }

    /* Delete the index entries associated with the current record.  */

    if( pPk ){
      j1 = sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, 0, regKey, nKey);
    }else{
      j1 = sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, 0, regOldRowid);

    }
    sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur, aRegIdx);
  
    /* If changing the record number, delete the old record.  */
    if( hasFK || chngKey || pPk!=0 ){
      sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, 0);
    }

    if( sqlite3VdbeCurrentAddr(v)==j1+1 ){
      sqlite3VdbeChangeToNoop(v, j1);
    }else{
      sqlite3VdbeJumpHere(v, j1);

    }

    if( hasFK ){
      sqlite3FkCheck(pParse, pTab, 0, regNewRowid, aXRef, chngKey);
    }
  
    /* Insert the new index entries and the new record. */







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      if( aXRef[i]<0 && i!=pTab->iPKey ){
        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, regNew+i);
      }
    }
  }

  if( !isView ){
    int j1 = 0;           /* Address of jump instruction */
    int bReplace = 0;     /* True if REPLACE conflict resolution might happen */

    /* Do constraint checks. */
    assert( regOldRowid>0 );
    sqlite3GenerateConstraintChecks(pParse, pTab, aRegIdx, iDataCur, iIdxCur,
        regNewRowid, regOldRowid, chngKey, onError, labelContinue, &bReplace);

    /* Do FK constraint checks. */
    if( hasFK ){
      sqlite3FkCheck(pParse, pTab, regOldRowid, 0, aXRef, chngKey);
    }

    /* Delete the index entries associated with the current record.  */
    if( bReplace || chngKey ){
      if( pPk ){
        j1 = sqlite3VdbeAddOp4Int(v, OP_NotFound, iDataCur, 0, regKey, nKey);
      }else{
        j1 = sqlite3VdbeAddOp3(v, OP_NotExists, iDataCur, 0, regOldRowid);
      }
    }
    sqlite3GenerateRowIndexDelete(pParse, pTab, iDataCur, iIdxCur, aRegIdx);
  
    /* If changing the record number, delete the old record.  */
    if( hasFK || chngKey || pPk!=0 ){
      sqlite3VdbeAddOp2(v, OP_Delete, iDataCur, 0);
    }
    if( bReplace || chngKey ){
      if( sqlite3VdbeCurrentAddr(v)==j1+1 ){
        sqlite3VdbeChangeToNoop(v, j1);
      }else{
        sqlite3VdbeJumpHere(v, j1);
      }
    }

    if( hasFK ){
      sqlite3FkCheck(pParse, pTab, 0, regNewRowid, aXRef, chngKey);
    }
  
    /* Insert the new index entries and the new record. */