| Commit message (Collapse) | Author | Age | Files | Lines | |
|---|---|---|---|---|---|
| * | MDEV-7486: Condition pushdown from HAVING into WHERE | Galina Shalygina | 2019-02-17 | 1 | -1/+1 |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Condition can be pushed from the HAVING clause into the WHERE clause if it depends only on the fields that are used in the GROUP BY list or depends on the fields that are equal to grouping fields. Aggregate functions can't be pushed down. How the pushdown is performed on the example: SELECT t1.a,MAX(t1.b) FROM t1 GROUP BY t1.a HAVING (t1.a>2) AND (MAX(c)>12); => SELECT t1.a,MAX(t1.b) FROM t1 WHERE (t1.a>2) GROUP BY t1.a HAVING (MAX(c)>12); The implementation scheme: 1. Extract the most restrictive condition cond from the HAVING clause of the select that depends only on the fields that are used in the GROUP BY list of the select (directly or indirectly through equalities) 2. Save cond as a condition that can be pushed into the WHERE clause of the select 3. Remove cond from the HAVING clause if it is possible The optimization is implemented in the function st_select_lex::pushdown_from_having_into_where(). New test file having_cond_pushdown.test is created. | ||||
| * | Fixed the results after the merge of 10.4 into bb-10.4-mdev16188. | Igor Babaev | 2019-02-03 | 1 | -1/+2 |
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| * | MDEV-16188 Use in-memory PK filters built from range index scans | Igor Babaev | 2019-02-03 | 1 | -2/+5 |
| | | | | | | | | | | | | | | | | | | | | | | | This patch contains a full implementation of the optimization that allows to use in-memory rowid / primary filters built for range conditions over indexes. In many cases usage of such filters reduce the number of disk seeks spent for fetching table rows. In this implementation the choice of what possible filter to be applied (if any) is made purely on cost-based considerations. This implementation re-achitectured the partial implementation of the feature pushed by Galina Shalygina in the commit 8d5a11122c32f4d9eb87536886c6e893377bdd07. Besides this patch contains a better implementation of the generic handler function handler::multi_range_read_info_const() that takes into account gaps between ranges when calculating the cost of range index scans. It also contains some corrections of the implementation of the handler function records_in_range() for MyISAM. This patch supports the feature for InnoDB and MyISAM. | ||||
| * | Create 'main' test directory and move 't' and 'r' there | Michael Widenius | 2018-03-29 | 1 | -0/+641 |
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index : delta/mariadb-git.git | |
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