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Overview
Comment: | Improve the accuracy of the estimates used when searching an index for values not present in any stat4 samples under some circumstances. |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | stat4-avgeq |
Files: | files | file ages | folders |
SHA1: |
e6f7f97dbc677c9f01b23142928c3fa7 |
User & Date: | dan 2014-10-03 19:16:53.018 |
Context
2014-10-03
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19:29 | Fix a division-by-zero error that might occur if the sqlite_stat1 table is corrupt. (check-in: f9c053b23e user: dan tags: stat4-avgeq) | |
19:16 | Improve the accuracy of the estimates used when searching an index for values not present in any stat4 samples under some circumstances. (check-in: e6f7f97dbc user: dan tags: stat4-avgeq) | |
16:00 | Add requirements marks on the sqlite3_db_status() interface implementation. Fix a typo in the documentation. Fix the new sqlite3_result_text64() routine so that it works correctly with an encoding parameter of SQLITE_UTF16. (check-in: d2fc322728 user: drh tags: trunk) | |
Changes
Changes to src/analyze.c.
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1444 1445 1446 1447 1448 1449 1450 | while( (c=z[0])>='0' && c<='9' ){ v = v*10 + c - '0'; z++; } #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 if( aOut ){ aOut[i] = v; | < > < > | 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 | while( (c=z[0])>='0' && c<='9' ){ v = v*10 + c - '0'; z++; } #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 if( aOut ){ aOut[i] = v; } #else assert( aOut==0 ); UNUSED_PARAMETER(aOut); #endif if( aLog ){ aLog[i] = sqlite3LogEst(v); } if( *z==' ' ) z++; } #ifndef SQLITE_ENABLE_STAT3_OR_STAT4 assert( pIndex!=0 ); #else |
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1512 1513 1514 1515 1516 1517 1518 1519 | pIndex = sqlite3PrimaryKeyIndex(pTable); }else{ pIndex = sqlite3FindIndex(pInfo->db, argv[1], pInfo->zDatabase); } z = argv[2]; if( pIndex ){ pIndex->bUnordered = 0; | > > > > > > > > | | 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 | pIndex = sqlite3PrimaryKeyIndex(pTable); }else{ pIndex = sqlite3FindIndex(pInfo->db, argv[1], pInfo->zDatabase); } z = argv[2]; if( pIndex ){ int nCol = pIndex->nKeyCol+1; #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 tRowcnt * const aiRowEst = pIndex->aiRowEst = (tRowcnt*)sqlite3DbMallocZero( pInfo->db, sizeof(tRowcnt) * nCol ); #else tRowcnt * const aiRowEst = 0; #endif pIndex->bUnordered = 0; decodeIntArray((char*)z, nCol, aiRowEst, pIndex->aiRowLogEst, pIndex); if( pIndex->pPartIdxWhere==0 ) pTable->nRowLogEst = pIndex->aiRowLogEst[0]; }else{ Index fakeIdx; fakeIdx.szIdxRow = pTable->szTabRow; #ifdef SQLITE_ENABLE_COSTMULT fakeIdx.pTable = pTable; #endif |
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1572 1573 1574 1575 1576 1577 1578 1579 1580 | ** sample columns except the last. The last is always set to 1, as ** once the trailing PK fields are considered all index keys are ** unique. */ nCol = pIdx->nSampleCol-1; pIdx->aAvgEq[nCol] = 1; } for(iCol=0; iCol<nCol; iCol++){ int i; /* Used to iterate through samples */ tRowcnt sumEq = 0; /* Sum of the nEq values */ | > < > > > > > > | > > > > | > | | | < > | | > | | > | | 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 | ** sample columns except the last. The last is always set to 1, as ** once the trailing PK fields are considered all index keys are ** unique. */ nCol = pIdx->nSampleCol-1; pIdx->aAvgEq[nCol] = 1; } for(iCol=0; iCol<nCol; iCol++){ int nSample = pIdx->nSample; int i; /* Used to iterate through samples */ tRowcnt sumEq = 0; /* Sum of the nEq values */ tRowcnt avgEq = 0; tRowcnt nRow; /* Number of rows in index */ i64 nSum100 = 0; /* Number of terms contributing to sumEq */ i64 nDist100; /* Number of distinct values in index */ if( pIdx->aiRowEst==0 ){ nRow = pFinal->anLt[iCol]; nDist100 = (i64)100 * pFinal->anDLt[iCol]; nSample--; }else{ nRow = pIdx->aiRowEst[0]; nDist100 = ((i64)100 * pIdx->aiRowEst[0]) / pIdx->aiRowEst[iCol+1]; } /* Set nSum to the number of distinct (iCol+1) field prefixes that ** occur in the stat4 table for this index. Set sumEq to the sum of ** the nEq values for column iCol for the same set (adding the value ** only once where there exist duplicate prefixes). */ for(i=0; i<nSample; i++){ if( i==(pIdx->nSample-1) || aSample[i].anDLt[iCol]!=aSample[i+1].anDLt[iCol] ){ sumEq += aSample[i].anEq[iCol]; nSum100 += 100; } } if( nDist100>nSum100 ){ avgEq = ((i64)100 * (nRow - sumEq))/(nDist100 - nSum100); } if( avgEq==0 ) avgEq = 1; pIdx->aAvgEq[iCol] = avgEq; } } } |
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1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 | /* Load the statistics from the sqlite_stat4 table. */ #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 if( rc==SQLITE_OK ){ int lookasideEnabled = db->lookaside.bEnabled; db->lookaside.bEnabled = 0; rc = loadStat4(db, sInfo.zDatabase); db->lookaside.bEnabled = lookasideEnabled; } #endif if( rc==SQLITE_NOMEM ){ db->mallocFailed = 1; } return rc; } #endif /* SQLITE_OMIT_ANALYZE */ | > > > > > | 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 | /* Load the statistics from the sqlite_stat4 table. */ #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 if( rc==SQLITE_OK ){ int lookasideEnabled = db->lookaside.bEnabled; db->lookaside.bEnabled = 0; rc = loadStat4(db, sInfo.zDatabase); db->lookaside.bEnabled = lookasideEnabled; } for(i=sqliteHashFirst(&db->aDb[iDb].pSchema->idxHash);i;i=sqliteHashNext(i)){ Index *pIdx = sqliteHashData(i); sqlite3DbFree(db, pIdx->aiRowEst); pIdx->aiRowEst = 0; } #endif if( rc==SQLITE_NOMEM ){ db->mallocFailed = 1; } return rc; } #endif /* SQLITE_OMIT_ANALYZE */ |
Changes to src/sqliteInt.h.
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1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 | unsigned isResized:1; /* True if resizeIndexObject() has been called */ unsigned isCovering:1; /* True if this is a covering index */ #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 int nSample; /* Number of elements in aSample[] */ int nSampleCol; /* Size of IndexSample.anEq[] and so on */ tRowcnt *aAvgEq; /* Average nEq values for keys not in aSample */ IndexSample *aSample; /* Samples of the left-most key */ #endif }; /* ** Allowed values for Index.idxType */ #define SQLITE_IDXTYPE_APPDEF 0 /* Created using CREATE INDEX */ | > | 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 | unsigned isResized:1; /* True if resizeIndexObject() has been called */ unsigned isCovering:1; /* True if this is a covering index */ #ifdef SQLITE_ENABLE_STAT3_OR_STAT4 int nSample; /* Number of elements in aSample[] */ int nSampleCol; /* Size of IndexSample.anEq[] and so on */ tRowcnt *aAvgEq; /* Average nEq values for keys not in aSample */ IndexSample *aSample; /* Samples of the left-most key */ tRowcnt *aiRowEst; /* Non-logarithmic stat1 data for this table */ #endif }; /* ** Allowed values for Index.idxType */ #define SQLITE_IDXTYPE_APPDEF 0 /* Created using CREATE INDEX */ |
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