MDEV-26337: subquery with groupby and ROLLUP returns incorrect results on LEFT JOIN on INDEXED valuesbb-10.3-mdev26337-v2

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.

3 files changed, 82 insertions, 1 deletions

diff --git a/mysql-test/main/derived_split_innodb.result b/mysql-test/main/derived_split_innodb.result
index 7ea3b689f23..8162bfcdae7 100644
--- a/mysql-test/main/derived_split_innodb.result
+++ b/mysql-test/main/derived_split_innodb.result
@@ -234,4 +234,46 @@ id	itemid	id	id
 4	2	4	2
 drop table t1,t2,t3;
 set optimizer_switch='split_materialized=default';
+#
+# MDEV-26337: subquery with groupby and ROLLUP returns incorrect results 
+#  (The testcase is taken from testcase for MDEV-13389 due to it being
+#   much smaller)
+#
+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;
+Table	Op	Msg_type	Msg_text
+test.t3	analyze	status	OK
+test.t4	analyze	status	OK
+# 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;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t3	range	idx_b	idx_b	5	NULL	3	Using index condition; Using where
+1	PRIMARY	<derived2>	ref	key0	key0	133	test.t3.a,test.t3.c	2	
+2	LATERAL DERIVED	t4	ref	idx	idx	133	test.t3.a,test.t3.c	1	
+# ... 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;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t3	range	idx_b	idx_b	5	NULL	3	Using index condition; Using where
+1	PRIMARY	<derived2>	ref	key0	key0	133	test.t3.a,test.t3.c	4	
+2	DERIVED	t4	ALL	NULL	NULL	NULL	NULL	40	Using filesort
+drop table t3, t4;
 # End of 10.3 tests
diff --git a/mysql-test/main/derived_split_innodb.test b/mysql-test/main/derived_split_innodb.test
index 6f33c71eede..2a3565be36f 100644
--- a/mysql-test/main/derived_split_innodb.test
+++ b/mysql-test/main/derived_split_innodb.test
@@ -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
diff --git a/sql/opt_split.cc b/sql/opt_split.cc
index edf9ae3deff..8a985095f3c 100644
--- a/sql/opt_split.cc
+++ b/sql/opt_split.cc
@@ -310,6 +310,8 @@ struct SplM_field_ext_info: public SplM_field_info
        occurred also in the select list of this join
     9. There are defined some keys usable for ref access of fields from C
        with available statistics.
+    10. The select doesn't use WITH ROLLUP (This limitation can probably be
+       lifted)
 
   @retval
     true   if the answer is positive
@@ -326,7 +328,8 @@ bool JOIN::check_for_splittable_materialized()
       (unit->first_select()->next_select()) ||                        // !(3)
       (derived->prohibit_cond_pushdown) ||                            // !(4)
       (derived->is_recursive_with_table()) ||                         // !(5)
-      (table_count == 0 || const_tables == top_join_tab_count))       // !(6)
+      (table_count == 0 || const_tables == top_join_tab_count) ||     // !(6)
+      rollup.state != ROLLUP::STATE_NONE)                             // (10)
     return false;
   if (group_list)                                                     // (7.1)
   {