MDEV-18700 EXPLAIN EXTENDED shows a wrong operation for query

           with UNION ALL after INTERSECT

EXPLAIN EXTENDED erroneously showed UNION instead of UNION ALL in
the warning if UNION ALL followed INTERSECT or EXCEPT operations.
The bug was in the function st_select_lex_unit::print() that printed
the text of the query used in the warning.

1 files changed, 30 insertions, 0 deletions

diff --git a/mysql-test/main/union.test b/mysql-test/main/union.test
index e7543ba4a81..9d9194ebab6 100644
--- a/mysql-test/main/union.test
+++ b/mysql-test/main/union.test
@@ -1812,5 +1812,35 @@ SELECT c1 FROM t1 UNION SELECT - @a FROM t2;
 drop table t1,t2;
 
 --echo #
+--echo # MDEV-18700: EXPLAIN EXTENDED for query with UNION ALL
+--echo #             after INTERSECT/EXCEPT operations
+--echo #
+
+create table t1 (a int);
+insert into t1 values (3), (1), (7), (3), (2), (7), (4);
+
+create table t2 (a int);
+insert into t2 values (4), (5), (9), (1), (8), (9);
+
+create table t3 (a int);
+insert into t3 values (8), (1), (8), (2), (3), (7), (2);
+
+explain extended
+select * from t2 where a < 5
+intersect
+select * from t3 where a < 5
+union all
+select * from t1 where a > 4;
+
+explain extended
+select * from t2 where a < 5
+except
+select * from t3 where a < 5
+union all
+select * from t1 where a > 4;
+
+drop table t1,t2,t3;
+
+--echo #
 --echo # End of 10.3 tests
 --echo #