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Overview
| Comment: | Fix an obsolete comment on the whereRangeScanEst() routine. No changes to code. |
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| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: | b16bf8518b7c50f6a939aa54900fea91 |
| User & Date: | drh 2014-06-06 17:09:52 |
Context
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2014-06-06
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| 20:20 | Make sure the estLog() routine in the query planner handles negative values correctly (always returning 1). Prior to this change, estLog(-1) would return a large number which could throw off the cost computations in the query planner in obscure circumstances. check-in: 75437bee user: drh tags: trunk | |
| 17:09 | Fix an obsolete comment on the whereRangeScanEst() routine. No changes to code. check-in: b16bf851 user: drh tags: trunk | |
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2014-06-05
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| 11:15 | Fix a problem that was causing the FTS4 integrity-check command to fail if the table had one or more "notindexed" columns. check-in: 7123bb26 user: dan tags: trunk | |
Changes
Changes to src/where.c.
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** When this function is called, *pnOut is set to the sqlite3LogEst() of the ** number of rows that the index scan is expected to visit without ** considering the range constraints. If nEq is 0, this is the number of ** rows in the index. Assuming no error occurs, *pnOut is adjusted (reduced) ** to account for the range contraints pLower and pUpper. ** ** In the absence of sqlite_stat4 ANALYZE data, or if such data cannot be ** used, each range inequality reduces the search space by a factor of 4. ** Hence a pair of constraints (x>? AND x<?) reduces the expected number of ** rows visited by a factor of 16. */ static int whereRangeScanEst( Parse *pParse, /* Parsing & code generating context */ WhereLoopBuilder *pBuilder, WhereTerm *pLower, /* Lower bound on the range. ex: "x>123" Might be NULL */ WhereTerm *pUpper, /* Upper bound on the range. ex: "x<455" Might be NULL */ WhereLoop *pLoop /* Modify the .nOut and maybe .rRun fields */ |
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** When this function is called, *pnOut is set to the sqlite3LogEst() of the ** number of rows that the index scan is expected to visit without ** considering the range constraints. If nEq is 0, this is the number of ** rows in the index. Assuming no error occurs, *pnOut is adjusted (reduced) ** to account for the range contraints pLower and pUpper. ** ** In the absence of sqlite_stat4 ANALYZE data, or if such data cannot be ** used, a single range inequality reduces the search space by a factor of 4. ** and a pair of constraints (x>? AND x<?) reduces the expected number of ** rows visited by a factor of 64. */ static int whereRangeScanEst( Parse *pParse, /* Parsing & code generating context */ WhereLoopBuilder *pBuilder, WhereTerm *pLower, /* Lower bound on the range. ex: "x>123" Might be NULL */ WhereTerm *pUpper, /* Upper bound on the range. ex: "x<455" Might be NULL */ WhereLoop *pLoop /* Modify the .nOut and maybe .rRun fields */ |