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Overview
Comment:Omit an unnecessary OP_Null opcode from UPDATE.
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SHA1: 72d111336c5016e5b5092dfebcd01253266a7685
User & Date: drh 2013-12-19 02:56:01.711
Context
2013-12-19
14:34
Remove an unneeded column-cache flush in aggregate SELECT and an unreachable branch in the INSERT logic. (check-in: ffa092e13b user: drh tags: trunk)
02:56
Omit an unnecessary OP_Null opcode from UPDATE. (check-in: 72d111336c user: drh tags: trunk)
02:23
Omit one or more pointless instructions that occur in between OP_NoConflict and OP_Halt. (check-in: 61e2f3575c user: drh tags: trunk)
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/update.c.
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  ** the database after the BEFORE triggers are fired anyway (as the trigger 
  ** may have modified them). So not loading those that are not going to
  ** be used eliminates some redundant opcodes.
  */
  newmask = sqlite3TriggerColmask(
      pParse, pTrigger, pChanges, 1, TRIGGER_BEFORE, pTab, onError
  );
  sqlite3VdbeAddOp3(v, OP_Null, 0, regNew, regNew+pTab->nCol-1);
  for(i=0; i<pTab->nCol; i++){
    if( i==pTab->iPKey ){
      /*sqlite3VdbeAddOp2(v, OP_Null, 0, regNew+i);*/
    }else{
      j = aXRef[i];
      if( j>=0 ){
        sqlite3ExprCode(pParse, pChanges->a[j].pExpr, regNew+i);
      }else if( 0==(tmask&TRIGGER_BEFORE) || i>31 || (newmask&(1<<i)) ){
        /* This branch loads the value of a column that will not be changed 
        ** into a register. This is done if there are no BEFORE triggers, or
        ** if there are one or more BEFORE triggers that use this value via
        ** a new.* reference in a trigger program.
        */
        testcase( i==31 );
        testcase( i==32 );
        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, regNew+i);


      }
    }
  }

  /* Fire any BEFORE UPDATE triggers. This happens before constraints are
  ** verified. One could argue that this is wrong.
  */







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  ** the database after the BEFORE triggers are fired anyway (as the trigger 
  ** may have modified them). So not loading those that are not going to
  ** be used eliminates some redundant opcodes.
  */
  newmask = sqlite3TriggerColmask(
      pParse, pTrigger, pChanges, 1, TRIGGER_BEFORE, pTab, onError
  );
  /*sqlite3VdbeAddOp3(v, OP_Null, 0, regNew, regNew+pTab->nCol-1);*/
  for(i=0; i<pTab->nCol; i++){
    if( i==pTab->iPKey ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regNew+i);
    }else{
      j = aXRef[i];
      if( j>=0 ){
        sqlite3ExprCode(pParse, pChanges->a[j].pExpr, regNew+i);
      }else if( 0==(tmask&TRIGGER_BEFORE) || i>31 || (newmask&(1<<i)) ){
        /* This branch loads the value of a column that will not be changed 
        ** into a register. This is done if there are no BEFORE triggers, or
        ** if there are one or more BEFORE triggers that use this value via
        ** a new.* reference in a trigger program.
        */
        testcase( i==31 );
        testcase( i==32 );
        sqlite3ExprCodeGetColumnOfTable(v, pTab, iDataCur, i, regNew+i);
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, regNew+i);
      }
    }
  }

  /* Fire any BEFORE UPDATE triggers. This happens before constraints are
  ** verified. One could argue that this is wrong.
  */