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Overview
| Comment: | Improved optimization of ORDER BY. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | orderby-fix |
| Files: | files | file ages | folders |
| SHA1: |
97e5c70f2f19a1bca70dd2221b757b9e |
| User & Date: | drh 2013-03-27 16:05:30 |
Context
|
2013-03-27
| ||
| 16:42 | Restore additional ORDER BY optimizations that where broken by the recent ORDER BY fix. Closed-Leaf check-in: c77ee6e2 user: drh tags: orderby-fix | |
| 16:05 | Improved optimization of ORDER BY. check-in: 97e5c70f user: drh tags: orderby-fix | |
| 15:04 | A fix and test-case for the ORDER BY problem identified by ticket [a179fe7465]. This change causes sorting to occur in some cases where it is not strictly necessary. Further work is needed to avoid those extra sorts. check-in: 488089e6 user: drh tags: orderby-fix | |
Changes
Changes to src/where.c.
3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 |
** on one page and hence more pages have to be fetched.
**
** The ANALYZE command and the sqlite_stat1 and sqlite_stat3 tables do
** not give us data on the relative sizes of table and index records.
** So this computation assumes table records are about twice as big
** as index records
*/
if( (pc.plan.wsFlags&~(WHERE_REVERSE|WHERE_ORDERED))==WHERE_IDX_ONLY
&& (pWC->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
&& sqlite3GlobalConfig.bUseCis
&& OptimizationEnabled(pParse->db, SQLITE_CoverIdxScan)
){
/* This index is not useful for indexing, but it is a covering index.
** A full-scan of the index might be a little faster than a full-scan
** of the table, so give this case a cost slightly less than a table
|
| > |
3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 |
** on one page and hence more pages have to be fetched.
**
** The ANALYZE command and the sqlite_stat1 and sqlite_stat3 tables do
** not give us data on the relative sizes of table and index records.
** So this computation assumes table records are about twice as big
** as index records
*/
if( (pc.plan.wsFlags&~(WHERE_REVERSE|WHERE_ORDERED|WHERE_OB_UNIQUE))
==WHERE_IDX_ONLY
&& (pWC->wctrlFlags & WHERE_ONEPASS_DESIRED)==0
&& sqlite3GlobalConfig.bUseCis
&& OptimizationEnabled(pParse->db, SQLITE_CoverIdxScan)
){
/* This index is not useful for indexing, but it is a covering index.
** A full-scan of the index might be a little faster than a full-scan
** of the table, so give this case a cost slightly less than a table
|