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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. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | trunk |
Files: | files | file ages | folders |
SHA1: |
8125b74cb46c372b9a319f6270f1c396 |
User & Date: | drh 2015-10-16 12:53:47.105 |
Context
2015-10-16
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13:50 | Simplify the OP_Column logic slightly. One very small performance improvement added. (check-in: 0114b45dc2 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: 8125b74cb4 user: drh tags: trunk) | |
12:39 | Improved header comment on the tool/vdbe_profile.tcl script. No changes to code. (check-in: b17ad8fc04 user: drh tags: trunk) | |
Changes
Changes to src/vdbe.c.
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2436 2437 2438 2439 2440 2441 2442 | } } pC->cacheStatus = p->cacheCtr; pC->iHdrOffset = getVarint32(pC->aRow, offset); pC->nHdrParsed = 0; aOffset[0] = offset; | < < < < < < < < < < < < < > > > > > > > > > > > > > > | 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 */ |
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