/ Check-in [8125b74c]
Login

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

Overview
Comment: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.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA1:8125b74cb46c372b9a319f6270f1c396767accd7
User & Date: drh 2015-10-16 12:53:47
Context
2015-10-16
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
12:39
Improved header comment on the tool/vdbe_profile.tcl script. No changes to code. check-in: b17ad8fc user: drh tags: trunk
Changes
Hide Diffs Unified Diffs Ignore Whitespace Patch

Changes to src/vdbe.c.

2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463














2464
2465
2466
2467
2468
2469
2470
      }
    }
    pC->cacheStatus = p->cacheCtr;
    pC->iHdrOffset = getVarint32(pC->aRow, offset);
    pC->nHdrParsed = 0;
    aOffset[0] = offset;

    /* Make sure a corrupt database has not given us an oversize header.
    ** Do this now to avoid an oversize memory allocation.
    **
    ** Type entries can be between 1 and 5 bytes each.  But 4 and 5 byte
    ** types use so much data space that there can only be 4096 and 32 of
    ** them, respectively.  So the maximum header length results from a
    ** 3-byte type for each of the maximum of 32768 columns plus three
    ** extra bytes for the header length itself.  32768*3 + 3 = 98307.
    */
    if( offset > 98307 || offset > pC->payloadSize ){
      rc = SQLITE_CORRUPT_BKPT;
      goto op_column_error;
    }

    if( avail<offset ){
      /* pC->aRow does not have to hold the entire row, but it does at least
      ** need to cover the header of the record.  If pC->aRow does not contain
      ** the complete header, then set it to zero, forcing the header to be
      ** dynamically allocated. */
      pC->aRow = 0;
      pC->szRow = 0;














    }

    /* The following goto is an optimization.  It can be omitted and
    ** everything will still work.  But OP_Column is measurably faster
    ** by skipping the subsequent conditional, which is always true.
    */
    assert( pC->nHdrParsed<=p2 );         /* Conditional skipped */







<
<
<
<
<
<
<
<
<
<
<
<
<








>
>
>
>
>
>
>
>
>
>
>
>
>
>







2436
2437
2438
2439
2440
2441
2442













2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
      }
    }
    pC->cacheStatus = p->cacheCtr;
    pC->iHdrOffset = getVarint32(pC->aRow, offset);
    pC->nHdrParsed = 0;
    aOffset[0] = offset;















    if( avail<offset ){
      /* pC->aRow does not have to hold the entire row, but it does at least
      ** need to cover the header of the record.  If pC->aRow does not contain
      ** the complete header, then set it to zero, forcing the header to be
      ** dynamically allocated. */
      pC->aRow = 0;
      pC->szRow = 0;

      /* Make sure a corrupt database has not given us an oversize header.
      ** Do this now to avoid an oversize memory allocation.
      **
      ** Type entries can be between 1 and 5 bytes each.  But 4 and 5 byte
      ** types use so much data space that there can only be 4096 and 32 of
      ** them, respectively.  So the maximum header length results from a
      ** 3-byte type for each of the maximum of 32768 columns plus three
      ** extra bytes for the header length itself.  32768*3 + 3 = 98307.
      */
      if( offset > 98307 || offset > pC->payloadSize ){
        rc = SQLITE_CORRUPT_BKPT;
        goto op_column_error;
      }
    }

    /* The following goto is an optimization.  It can be omitted and
    ** everything will still work.  But OP_Column is measurably faster
    ** by skipping the subsequent conditional, which is always true.
    */
    assert( pC->nHdrParsed<=p2 );         /* Conditional skipped */