A fix and test case for Bug#6088 "FOUND_ROWS returns wrong values for

prepared statements when LIMIT is used" and post-review comments.
The fix changes the approach we calculate the need for ORDER BY 
in UNION: the previous was not PS friendly, as it damaged SELECT_LEX 
options in case of single select.

3 files changed, 41 insertions, 3 deletions

diff --git a/mysql-test/r/ps.result b/mysql-test/r/ps.result
index 0950a066e64..036d50efbba 100644
--- a/mysql-test/r/ps.result
+++ b/mysql-test/r/ps.result
@@ -410,3 +410,27 @@ a	a
 1.1	1.2
 2.1	2.2
 deallocate prepare stmt;
+create table t1 (a int);
+insert into t1 (a) values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
+prepare stmt from "select sql_calc_found_rows * from t1 limit 2";
+execute stmt;
+a
+1
+2
+select found_rows();
+found_rows()
+10
+execute stmt;
+a
+1
+2
+select found_rows();
+found_rows()
+10
+execute stmt;
+a
+1
+2
+select found_rows();
+found_rows()
+10
diff --git a/mysql-test/r/subselect.result b/mysql-test/r/subselect.result
index 8bcf7f9bff2..04c5f685f58 100644
--- a/mysql-test/r/subselect.result
+++ b/mysql-test/r/subselect.result
@@ -176,17 +176,17 @@ a	b
 a	b
 1	7
 2	7
-3	8
 4	8
+3	8
 explain extended (select * from t2 where t2.b=(select a from t3 order by 1 desc limit 1)) union (select * from t4 where t4.b=(select max(t2.a)*4 from t2) order by a);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	2	Using where
 2	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	Using filesort
-3	UNION	t4	ALL	NULL	NULL	NULL	NULL	3	Using where; Using filesort
+3	UNION	t4	ALL	NULL	NULL	NULL	NULL	3	Using where
 4	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	
 NULL	UNION RESULT	<union1,3>	ALL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	(select test.t2.a AS `a`,test.t2.b AS `b` from test.t2 where (test.t2.b = (select test.t3.a AS `a` from test.t3 order by test.t3.a desc limit 1))) union (select test.t4.a AS `a`,test.t4.b AS `b` from test.t4 where (test.t4.b = (select (max(test.t2.a) * 4) AS `max(t2.a)*4` from test.t2)) order by test.t4.a)
+Note	1003	(select test.t2.a AS `a`,test.t2.b AS `b` from test.t2 where (test.t2.b = (select test.t3.a AS `a` from test.t3 order by test.t3.a desc limit 1))) union (select test.t4.a AS `a`,test.t4.b AS `b` from test.t4 where (test.t4.b = (select (max(test.t2.a) * 4) AS `max(t2.a)*4` from test.t2)) order by a)
 select (select a from t3 where a<t2.a*4 order by 1 desc limit 1), a from t2;
 (select a from t3 where a<t2.a*4 order by 1 desc limit 1)	a
 3	1
diff --git a/mysql-test/t/ps.test b/mysql-test/t/ps.test
index 04ab8aa62a8..5a32080a4c7 100644
--- a/mysql-test/t/ps.test
+++ b/mysql-test/t/ps.test
@@ -415,3 +415,17 @@ execute stmt;
 execute stmt;
 execute stmt;
 deallocate prepare stmt;
+
+#
+# Bug#6088 "FOUND_ROWS returns wrong values for prepared statements when
+# LIMIT is used"
+# 
+create table t1 (a int);
+insert into t1 (a) values (1), (2), (3), (4), (5), (6), (7), (8), (9), (10);
+prepare stmt from "select sql_calc_found_rows * from t1 limit 2";
+execute stmt;
+select found_rows();
+execute stmt;
+select found_rows();
+execute stmt;
+select found_rows();