diff options
| author | Igor Babaev <igor@askmonty.org> | 2022-06-19 23:43:17 -0700 |
|---|---|---|
| committer | Igor Babaev <igor@askmonty.org> | 2022-06-20 16:43:44 -0700 |
| commit | 2adebf4876283859066c11f23e89965733594363 (patch) | |
| tree | c7bb7ab6f94b4d34c9adab2bab466f37b3ed7f56 /sql/sql_delete.cc | |
| parent | f7d2374083184261897e86bced158d9ae2c4aaaf (diff) | |
| download | mariadb-git-bb-10.10-mdev-7487.tar.gz | |
MDEV-7487 Semi-join optimization for single-table update/delete statementsbb-10.10-mdev-7487
This patch allows to use semi-join optimization at the top level of
single-table update and delete statements.
The problem of supporting such optimization became easy to resolve after
processing a single-table update/delete statement started using JOIN
structure. This allowed to use JOIN::prepare() not only for multi-table
updates/deletes but for single-table ones as well. This was done in the
patch for mdev-28883:
Re-design the upper level of handling UPDATE and DELETE statements.
Note that JOIN::prepare() detects all subqueries that can be considered
as candidates for semi-join optimization. The code added by this patch
looks for such candidates at the top level and if such candidates are found
in the processed single-table update/delete the statement is handled in
the same way as a multi-table update/delete.
Approved by Oleksandr Byelkin <sanja@mariadb.com>
Diffstat (limited to 'sql/sql_delete.cc')
| -rw-r--r-- | sql/sql_delete.cc | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/sql/sql_delete.cc b/sql/sql_delete.cc index 2ff43316954..ed4b6beab34 100644 --- a/sql/sql_delete.cc +++ b/sql/sql_delete.cc @@ -1591,10 +1591,16 @@ bool Sql_cmd_delete::prepare_inner(THD *thd) select_lex->order_list.first, false, NULL, NULL, NULL, select_lex, &lex->unit))) - { goto err; } + + if (!multitable && + select_lex->sj_subselects.elements) + multitable= true; + + if (!multitable) + ((multi_delete *)result)->set_delete_tables(0); } if (multitable) @@ -1638,7 +1644,8 @@ bool Sql_cmd_delete::prepare_inner(THD *thd) { TABLE_LIST *duplicate; if ((duplicate= unique_table(thd, target_tbl->correspondent_table, - lex->query_tables, 0))) + lex->query_tables, 0)) && + !duplicate->select_lex->is_sj_subselect_lifted_to_top()) { update_non_unique_table_error(target_tbl->correspondent_table, "DELETE", duplicate); |