/ Check-in [0114b45d]
Login
SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Many hyperlinks are disabled.
Use anonymous login to enable hyperlinks.

Overview
Comment:Simplify the OP_Column logic slightly. One very small performance improvement added.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1: 0114b45dc286c13db0d640f0486d8a5bef9ff078
User & Date: drh 2015-10-16 13:50:08
Context
2015-10-16
14:23
Use a lookup table to compute the content length for serial types less than 128, for a 1.2% performance improvement. check-in: 33957248 user: drh tags: trunk
13:50
Simplify the OP_Column logic slightly. One very small performance improvement added. check-in: 0114b45d user: drh tags: trunk
12:53
OP_Column optimization: Do not check for an oversize row header unless the row header size is larger than the content available on the local page. check-in: 8125b74c user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/vdbe.c.

2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
....
2544
2545
2546
2547
2548
2549
2550


2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
    ** to extract additional fields up through the p2+1-th field 
    */
    op_column_read_header:
    if( pC->iHdrOffset<aOffset[0] ){
      /* Make sure zData points to enough of the record to cover the header. */
      if( pC->aRow==0 ){
        memset(&sMem, 0, sizeof(sMem));
        rc = sqlite3VdbeMemFromBtree(pCrsr, 0, aOffset[0], 
                                     !pC->isTable, &sMem);
        if( rc!=SQLITE_OK ){
          goto op_column_error;
        }
        zData = (u8*)sMem.z;
      }else{
        zData = pC->aRow;
      }
  
      /* Fill in pC->aType[i] and aOffset[i] values through the p2-th field. */
      i = pC->nHdrParsed;
      offset64 = aOffset[i];
      zHdr = zData + pC->iHdrOffset;
      zEndHdr = zData + aOffset[0];
      assert( i<=p2 && zHdr<zEndHdr );
      do{
        if( zHdr[0]<0x80 ){
          t = zHdr[0];
          zHdr++;
        }else{
          zHdr += sqlite3GetVarint32(zHdr, &t);
        }
        pC->aType[i] = t;
        szField = sqlite3VdbeSerialTypeLen(t);
        offset64 += szField;
        i++;
        aOffset[i] = (u32)(offset64 & 0xffffffff);
      }while( i<=p2 && zHdr<zEndHdr );
      pC->nHdrParsed = i;
      pC->iHdrOffset = (u32)(zHdr - zData);
      if( pC->aRow==0 ){
        sqlite3VdbeMemRelease(&sMem);
        sMem.flags = MEM_Null;
      }
  
      /* The record is corrupt if any of the following are true:
      ** (1) the bytes of the header extend past the declared header size
      **          (zHdr>zEndHdr)
      ** (2) the entire header was used but not all data was used
      **          (zHdr==zEndHdr && offset64!=pC->payloadSize)
      ** (3) the end of the data extends beyond the end of the record.
      **          (offset64 > pC->payloadSize)
      */
      if( (zHdr>=zEndHdr && (zHdr>zEndHdr || offset64!=pC->payloadSize))
       || (offset64 > pC->payloadSize)
      ){
        rc = SQLITE_CORRUPT_BKPT;
        goto op_column_error;
      }
................................................................................
      if( pOp->p4type==P4_MEM ){
        sqlite3VdbeMemShallowCopy(pDest, pOp->p4.pMem, MEM_Static);
      }else{
        sqlite3VdbeMemSetNull(pDest);
      }
      goto op_column_out;
    }


  }

  /* Extract the content for the p2+1-th column.  Control can only
  ** reach this point if aOffset[p2], aOffset[p2+1], and pC->aType[p2] are
  ** all valid.
  */
  assert( p2<pC->nHdrParsed );
  assert( rc==SQLITE_OK );
  assert( sqlite3VdbeCheckMemInvariants(pDest) );
  if( VdbeMemDynamic(pDest) ) sqlite3VdbeMemSetNull(pDest);
  t = pC->aType[p2];
  if( pC->szRow>=aOffset[p2+1] ){
    /* This is the common case where the desired content fits on the original
    ** page - where the content is not on an overflow page */
    sqlite3VdbeSerialGet(pC->aRow+aOffset[p2], t, pDest);
  }else{
    /* This branch happens only when content is on overflow pages */
    if( ((pOp->p5 & (OPFLAG_LENGTHARG|OPFLAG_TYPEOFARG))!=0







|
<
<
|
<












<
|












<
|
<
<



<

<

<







 







>
>










|







2480
2481
2482
2483
2484
2485
2486
2487


2488

2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500

2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513

2514


2515
2516
2517

2518

2519

2520
2521
2522
2523
2524
2525
2526
....
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
    ** to extract additional fields up through the p2+1-th field 
    */
    op_column_read_header:
    if( pC->iHdrOffset<aOffset[0] ){
      /* Make sure zData points to enough of the record to cover the header. */
      if( pC->aRow==0 ){
        memset(&sMem, 0, sizeof(sMem));
        rc = sqlite3VdbeMemFromBtree(pCrsr, 0, aOffset[0], !pC->isTable, &sMem);


        if( rc!=SQLITE_OK ) goto op_column_error;

        zData = (u8*)sMem.z;
      }else{
        zData = pC->aRow;
      }
  
      /* Fill in pC->aType[i] and aOffset[i] values through the p2-th field. */
      i = pC->nHdrParsed;
      offset64 = aOffset[i];
      zHdr = zData + pC->iHdrOffset;
      zEndHdr = zData + aOffset[0];
      assert( i<=p2 && zHdr<zEndHdr );
      do{

        if( (t = zHdr[0])<0x80 ){
          zHdr++;
        }else{
          zHdr += sqlite3GetVarint32(zHdr, &t);
        }
        pC->aType[i] = t;
        szField = sqlite3VdbeSerialTypeLen(t);
        offset64 += szField;
        i++;
        aOffset[i] = (u32)(offset64 & 0xffffffff);
      }while( i<=p2 && zHdr<zEndHdr );
      pC->nHdrParsed = i;
      pC->iHdrOffset = (u32)(zHdr - zData);

      if( pC->aRow==0 ) sqlite3VdbeMemRelease(&sMem);


  
      /* The record is corrupt if any of the following are true:
      ** (1) the bytes of the header extend past the declared header size

      ** (2) the entire header was used but not all data was used

      ** (3) the end of the data extends beyond the end of the record.

      */
      if( (zHdr>=zEndHdr && (zHdr>zEndHdr || offset64!=pC->payloadSize))
       || (offset64 > pC->payloadSize)
      ){
        rc = SQLITE_CORRUPT_BKPT;
        goto op_column_error;
      }
................................................................................
      if( pOp->p4type==P4_MEM ){
        sqlite3VdbeMemShallowCopy(pDest, pOp->p4.pMem, MEM_Static);
      }else{
        sqlite3VdbeMemSetNull(pDest);
      }
      goto op_column_out;
    }
  }else{
    t = pC->aType[p2];
  }

  /* Extract the content for the p2+1-th column.  Control can only
  ** reach this point if aOffset[p2], aOffset[p2+1], and pC->aType[p2] are
  ** all valid.
  */
  assert( p2<pC->nHdrParsed );
  assert( rc==SQLITE_OK );
  assert( sqlite3VdbeCheckMemInvariants(pDest) );
  if( VdbeMemDynamic(pDest) ) sqlite3VdbeMemSetNull(pDest);
  assert( t==pC->aType[p2] );
  if( pC->szRow>=aOffset[p2+1] ){
    /* This is the common case where the desired content fits on the original
    ** page - where the content is not on an overflow page */
    sqlite3VdbeSerialGet(pC->aRow+aOffset[p2], t, pDest);
  }else{
    /* This branch happens only when content is on overflow pages */
    if( ((pOp->p5 & (OPFLAG_LENGTHARG|OPFLAG_TYPEOFARG))!=0