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Overview
| Comment: | More details in the header comment of pushDownWhereTerms(). No changes to code. |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | prefer-coroutine-sort-subquery |
| Files: | files | file ages | folders |
| SHA3-256: |
928486231ff7cc0df17a5aa23a080a1b |
| User & Date: | drh 2017-09-30 11:47:06 |
Context
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2017-10-02
| ||
| 02:52 | The query planner now always prefers to implement a FROM-clause subquery using a co-routine rather than flattening the subquery into the outer query. check-in: c9104b59 user: drh tags: trunk | |
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2017-09-30
| ||
| 11:47 | More details in the header comment of pushDownWhereTerms(). No changes to code. Closed-Leaf check-in: 92848623 user: drh tags: prefer-coroutine-sort-subquery | |
| 10:50 | Make sure the SQLITE_Stat34 optimization switch is always 0x800, a value which is hard-coded in the TH3 test suite. check-in: 6aed4ea3 user: drh tags: prefer-coroutine-sort-subquery | |
Changes
Changes to src/select.c.
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** The hope is that the terms added to the inner query will make it more
** efficient.
**
** Do not attempt this optimization if:
**
** (1) (** This restriction was removed on 2017-09-29. We used to
** disallow this optimization for aggregate subqueries, but now
** it is allowed by putting the extra terms on the HAVING clause **)
**
** (2) The inner query is the recursive part of a common table expression.
**
** (3) The inner query has a LIMIT clause (since the changes to the WHERE
** close would change the meaning of the LIMIT).
**
** (4) The inner query is the right operand of a LEFT JOIN. (The caller
|
| > > > > |
3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 |
** The hope is that the terms added to the inner query will make it more ** efficient. ** ** Do not attempt this optimization if: ** ** (1) (** This restriction was removed on 2017-09-29. We used to ** disallow this optimization for aggregate subqueries, but now ** it is allowed by putting the extra terms on the HAVING clause. ** The added HAVING clause is pointless if the subquery lacks ** a GROUP BY clause. But such a HAVING clause is also harmless ** so there does not appear to be any reason to add extra logic ** to suppress it. **) ** ** (2) The inner query is the recursive part of a common table expression. ** ** (3) The inner query has a LIMIT clause (since the changes to the WHERE ** close would change the meaning of the LIMIT). ** ** (4) The inner query is the right operand of a LEFT JOIN. (The caller |