database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-29 05:21:33 +03:00
Code Activity

MDEV-28616 Crash when using derived table over union with order by clause

Browse Source 
This bug manifested itself when the server processed a query containing
a derived table over union whose ORDER BY clause included a subquery
with unresolvable column reference. For such a query the server crashed
when trying to resolve column references in the ORDER BY clause used by
union.
For any union with ORDER BY clause an extra SELECT_LEX structure is created
and it is attached to SELECT_LEX_UNIT structure of the union via the field
fake_select_lex. The outer context for fake_select_lex must be the same as
for other selects of the union. If the union is used in the FROM list of
a derived table then the outer context for fake_select_lex must be set to
NULL in line with other selects of the union. It was not done and it
caused a crash when searching for possible resolution of an unresolvable
column reference occurred in a subquery used in the ORDER BY clause.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
This commit is contained in:
Igor Babaev
2023-01-25 11:46:28 -08:00
parent 2279dddad6
commit 4652260d65
3 changed files with 56 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
sql/sql_derived.cc
View File

@ -771,6 +771,9 @@ bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived)
cursor->outer_join|= JOIN_TYPE_OUTER;
}
}
// Prevent it for possible ORDER BY clause
if (unit->fake_select_lex)
unit->fake_select_lex->context.outer_context= 0;
/*
Above cascade call of prepare is important for PS protocol, but after it