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Overview
| Comment: | Clarification to a comment in where.c. No code changes. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: |
04507c176330a06b09dcafa35ec0ca74 |
| User & Date: | drh 2013-01-15 16:15:28 |
Context
|
2013-01-15
| ||
| 18:49 | Fix a missing word in a comment. Enhance the "wheretrace" debugging output to show the estimated cost of each table option while planning the join order. check-in: ac4e119a user: drh tags: trunk | |
| 16:15 | Clarification to a comment in where.c. No code changes. check-in: 04507c17 user: drh tags: trunk | |
|
2013-01-11
| ||
| 09:58 | Add another test for the fts4 content= option. check-in: 7e6007a0 user: dan tags: trunk | |
Changes
Changes to src/where.c.
5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 |
** that do not use indices. But this nRow reduction only happens if the
** table really is the innermost join.
**
** The second loop iteration is only performed if no optimal scan
** strategies were found by the first iteration. This second iteration
** is used to search for the lowest cost scan overall.
**
** Previous versions of SQLite performed only the second iteration -
** the next outermost loop was always that with the lowest overall
** cost. However, this meant that SQLite could select the wrong plan
** for scripts such as the following:
**
** CREATE TABLE t1(a, b);
** CREATE TABLE t2(c, d);
** SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
**
** The best strategy is to iterate through table t1 first. However it
** is not possible to determine this with a simple greedy algorithm.
|
| | < < |
5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 |
** that do not use indices. But this nRow reduction only happens if the
** table really is the innermost join.
**
** The second loop iteration is only performed if no optimal scan
** strategies were found by the first iteration. This second iteration
** is used to search for the lowest cost scan overall.
**
** Without the optimal scan step (the first iteration) a suboptimal
** plan might be chosen for queries like this:
**
** CREATE TABLE t1(a, b);
** CREATE TABLE t2(c, d);
** SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
**
** The best strategy is to iterate through table t1 first. However it
** is not possible to determine this with a simple greedy algorithm.
|