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MDEV-26337: subquery with groupby and ROLLUP returns incorrect results on LEFT JOIN on INDEXED values

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Disable LATERAL DERIVED optimization for subqueries that have WITH ROLLUP.

This bug could affect queries with grouping derived tables / views / CTEs
with ROLLUP. The bug could manifest itself if the corresponding
materialized derived tables are subject to split optimization.

The current implementation of the split optimization produces rows
from the derived table in an arbitrary order. So these rows must be
accumulated in another temporary table and sorted according to the
used GROUP BY clause in order to be able to generate the additional
ROLLUP rows.

This patch prohibits to use split optimization for grouping derived
tables / views / CTEs with ROLLUP.
This commit is contained in:
Sergei Petrunia
2022-01-04 00:01:52 +03:00
parent 25f598f54f
commit c04adce8ac
3 changed files with 82 additions and 1 deletions
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36
mysql-test/main/derived_split_innodb.test
View File

@ -186,4 +186,40 @@ eval $q;
drop table t1,t2,t3;
set optimizer_switch='split_materialized=default';
--echo #
--echo # MDEV-26337: subquery with groupby and ROLLUP returns incorrect results
--echo # (The testcase is taken from testcase for MDEV-13389 due to it being
--echo # much smaller)
--echo #
create table t3 (a int, b int, c char(127), index idx_b(b)) engine=myisam;
insert into t3 values
(8,11,'aa'), (5,15,'cc'), (1,14,'bb'), (2,12,'aa'), (7,17,'cc'),
(7,18,'aa'), (2,11,'aa'), (7,10,'bb'), (3,11,'dd'), (4,12,'ee'),
(5,14,'dd'), (9,12,'ee');
create table t4 (a int, b int, c char(127), index idx(a,c)) engine=myisam;
insert into t4 values
(7,10,'cc'), (1,20,'aa'), (2,23,'bb'), (7,18,'cc'), (1,30,'bb'),
(4,71,'xx'), (3,15,'aa'), (7,82,'aa'), (8,12,'dd'), (4,15,'aa'),
(11,33,'yy'), (10,42,'zz'), (4,53,'xx'), (10,17,'yy'), (7,12,'cc'),
(8,20,'dd'), (7,32,'bb'), (1,50,'aa'), (3,40,'bb'), (3,77,'aa');
insert into t4 select a+10, b+10, concat(c,'f') from t4;
analyze table t3,t4;
--echo # This should use a plan with LATERAL DERIVED:
explain select t3.a,t3.c,t.max,t.min
from t3 join
(select a, c, max(b) max, min(b) min from t4 group by a,c) t
on t3.a=t.a and t3.c=t.c
where t3.b > 15;
--echo # ... and if one adds WITH ROLLUP, then LATERAL DERIVED is no longer used:
explain select t3.a,t3.c,t.max,t.min
from t3 join
(select a, c, max(b) max, min(b) min from t4 group by a,c with rollup) t
on t3.a=t.a and t3.c=t.c
where t3.b > 15;
drop table t3, t4;
--echo # End of 10.3 tests