database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-08-01 03:47:19 +03:00
Code Activity

MDEV-10232: Scalar result of subquery changes after adding an outer select stmt

Browse Source 
In a subquery, we don't have to maintain order
Added a fix such that order is considered when there is a limit clause.
This commit is contained in:
Varun Gupta
2017-01-21 00:56:33 +05:30
parent 8a4d605500
commit 213fc700b6
3 changed files with 25 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
sql/sql_select.cc
View File

@ -1619,7 +1619,8 @@ JOIN::optimize_inner()
<fields> to ORDER BY <fields>. There are three exceptions:
- if skip_sort_order is set (see above), then we can simply skip
GROUP BY;
- if we are in a subquery, we don't have to maintain order
- if we are in a subquery, we don't have to maintain order unless there
is a limit clause in the subquery.
- we can only rewrite ORDER BY if the ORDER BY fields are 'compatible'
with the GROUP BY ones, i.e. either one is a prefix of another.
We only check if the ORDER BY is a prefix of GROUP BY. In this case
@ -1631,7 +1632,7 @@ JOIN::optimize_inner()
if (!order || test_if_subpart(group_list, order))
{
if (skip_sort_order ||
select_lex->master_unit()->item) // This is a subquery
(select_lex->master_unit()->item && select_limit == HA_POS_ERROR)) // This is a subquery
order= NULL;
else
order= group_list;