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Comment:Optimization to the comparison opcodes in the byte-code engine.
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SHA3-256:654935c7737f1a9e08fde9b220c543e86ff6e05910e2f08973a2f93ab2b3e028
User & Date: drh 2017-08-03 00:29:23
Context
2017-08-03
15:43
Fix some problems in RBU test cases. Also update RBU source code to better handle the trivial case where an RBU update is applied to a database zero pages in size. check-in: 7676b39b user: dan tags: trunk
00:29
Optimization to the comparison opcodes in the byte-code engine. check-in: 654935c7 user: drh tags: trunk
2017-08-02
22:43
In the KeyInfo object, refactor the nField and nXField elements into nKeyField and nAllField, which are more useful and run a little faster. check-in: aea5990e user: drh tags: trunk
Changes
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Changes to src/vdbe.c.

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        flags3 = (pIn3->flags & ~MEM_TypeMask) | (flags3 & MEM_TypeMask);
      }
    }
    assert( pOp->p4type==P4_COLLSEQ || pOp->p4.pColl==0 );
    res = sqlite3MemCompare(pIn3, pIn1, pOp->p4.pColl);
  }
compare_op:
  switch( pOp->opcode ){
    case OP_Eq:    res2 = res==0;     break;
    case OP_Ne:    res2 = res;        break;
    case OP_Lt:    res2 = res<0;      break;
    case OP_Le:    res2 = res<=0;     break;
    case OP_Gt:    res2 = res>0;      break;
    default:       res2 = res>=0;     break;










  }

  /* Undo any changes made by applyAffinity() to the input registers. */
  assert( (pIn1->flags & MEM_Dyn) == (flags1 & MEM_Dyn) );
  pIn1->flags = flags1;
  assert( (pIn3->flags & MEM_Dyn) == (flags3 & MEM_Dyn) );
  pIn3->flags = flags3;

  if( pOp->p5 & SQLITE_STOREP2 ){
    pOut = &aMem[pOp->p2];
    iCompare = res;
    res2 = res2!=0;  /* For this path res2 must be exactly 0 or 1 */
    if( (pOp->p5 & SQLITE_KEEPNULL)!=0 ){
      /* The KEEPNULL flag prevents OP_Eq from overwriting a NULL with 1
      ** and prevents OP_Ne from overwriting NULL with 0.  This flag
      ** is only used in contexts where either:
      **   (1) op==OP_Eq && (r[P2]==NULL || r[P2]==0)
      **   (2) op==OP_Ne && (r[P2]==NULL || r[P2]==1)
      ** Therefore it is not necessary to check the content of r[P2] for







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        flags3 = (pIn3->flags & ~MEM_TypeMask) | (flags3 & MEM_TypeMask);
      }
    }
    assert( pOp->p4type==P4_COLLSEQ || pOp->p4.pColl==0 );
    res = sqlite3MemCompare(pIn3, pIn1, pOp->p4.pColl);
  }
compare_op:
  /* At this point, res is negative, zero, or positive if reg[P1] is
  ** less than, equal to, or greater than reg[P3], respectively.  Compute
  ** the answer to this operator in res2, depending on what the comparison
  ** operator actually is.  The next block of code depends on the fact
  ** that the 6 comparison operators are consecutive integers in this
  ** order:  NE, EQ, GT, LE, LT, GE */
  assert( OP_Eq==OP_Ne+1 ); assert( OP_Gt==OP_Ne+2 ); assert( OP_Le==OP_Ne+3 );
  assert( OP_Lt==OP_Ne+4 ); assert( OP_Ge==OP_Ne+5 );
  if( res<0 ){                        /* ne, eq, gt, le, lt, ge */
    static const unsigned char aLTb[] = { 1,  0,  0,  1,  1,  0 };
    res2 = aLTb[pOp->opcode - OP_Ne];
  }else if( res==0 ){
    static const unsigned char aEQb[] = { 0,  1,  0,  1,  0,  1 };
    res2 = aEQb[pOp->opcode - OP_Ne];
  }else{
    static const unsigned char aGTb[] = { 1,  0,  1,  0,  0,  1 };
    res2 = aGTb[pOp->opcode - OP_Ne];
  }

  /* Undo any changes made by applyAffinity() to the input registers. */
  assert( (pIn1->flags & MEM_Dyn) == (flags1 & MEM_Dyn) );
  pIn1->flags = flags1;
  assert( (pIn3->flags & MEM_Dyn) == (flags3 & MEM_Dyn) );
  pIn3->flags = flags3;

  if( pOp->p5 & SQLITE_STOREP2 ){
    pOut = &aMem[pOp->p2];
    iCompare = res;

    if( (pOp->p5 & SQLITE_KEEPNULL)!=0 ){
      /* The KEEPNULL flag prevents OP_Eq from overwriting a NULL with 1
      ** and prevents OP_Ne from overwriting NULL with 0.  This flag
      ** is only used in contexts where either:
      **   (1) op==OP_Eq && (r[P2]==NULL || r[P2]==0)
      **   (2) op==OP_Ne && (r[P2]==NULL || r[P2]==1)
      ** Therefore it is not necessary to check the content of r[P2] for