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MDEV-25679 Wrong result selecting from simple view with LIMIT and ORDER BY

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This bug affected queries with views / derived_tables / CTEs whose
specifications were of the form
  (SELECT ... LIMIT <n>) ORDER BY ...
Units representing such specifications contains one SELECT_LEX structure
for (SELECT ... LIMIT <n>) and additionally SELECT_LEX structure for
fake_select_lex. This fact should have been taken into account in the
function mysql_derived_fill().

This patch has to be applied to 10.2 and 10.3 only.
This commit is contained in:
Igor Babaev 2021-06-21 16:15:07 -07:00
parent 773a07b655
commit cc0bd8431f
3 changed files with 39 additions and 1 deletions
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21
mysql-test/r/derived_view.result
View file

@ -3436,3 +3436,24 @@ Warnings:
Note 1003 select `test`.`t1`.`pk` AS `pk`,`test`.`t1`.`a` AS `a`,3 AS `d`,`test`.`t2`.`b` AS `b`,`test`.`t3`.`c` AS `c` from `test`.`t1` join `test`.`t2` join `test`.`t3` where `test`.`t1`.`a` = 3 and `test`.`t1`.`pk` <= 2
drop view v1;
drop table t1,t2,t3;
#
# MDEV-25679: view / derived table defined as ordered select with LIMIT
#
create table t1 (a int);
insert into t1 values (3), (7), (1);
create view v1 as (select a from t1 limit 2) order by a desc;
(select a from t1 limit 2) order by a desc;
a
7
3
select * from v1;
a
7
3
select * from ((select a from t1 limit 2) order by a desc) dt;
a
7
3
drop view v1;
drop table t1;
# End of 10.2 tests

17
mysql-test/t/derived_view.test
View file

@ -2249,3 +2249,20 @@ eval explain extended $q;
drop view v1;
drop table t1,t2,t3;
--echo #
--echo # MDEV-25679: view / derived table defined as ordered select with LIMIT
--echo #
create table t1 (a int);
insert into t1 values (3), (7), (1);
create view v1 as (select a from t1 limit 2) order by a desc;
(select a from t1 limit 2) order by a desc;
select * from v1;
select * from ((select a from t1 limit 2) order by a desc) dt;
drop view v1;
drop table t1;
--echo # End of 10.2 tests

2
sql/sql_derived.cc
View file

@ -1091,7 +1091,7 @@ bool mysql_derived_fill(THD *thd, LEX *lex, TABLE_LIST *derived)
res= derived->fill_recursive(thd);
}
}
else if (unit->is_union())
else if (unit->is_union() || unit->fake_select_lex)
{
// execute union without clean up
res= unit->exec();