Derived tables and union can now create distinct keys

The idea is that instead of marking all select_lex's with DISTINCT, we
only mark those that really need distinct result.

Benefits of this change:
- Temporary tables used with derived tables, UNION, IN are now smaller
  as duplicates are removed already on the insert phase.
- The optimizer can now produce better plans with EQ_REF. This can be
  seen from the tests where several queries does not anymore materialize
  derived tables twice.
- Queries affected by 'in_predicate_conversion_threshold' where large IN
  lists are converted to sub query produces better plans.

Other things:
- Removed on duplicate call to sel->init_select() in
  LEX::add_primary_to_query_expression_body()
- I moved the testing of
  tab->table->pos_in_table_list->is_materialized_derived()
  in join_read_const_table() to the caller as it caused problems for
  derived tables that could be proven to be const tables.
  This also is likely to fix some bugs as if join_read_const_table()
  was aborted, the table was left marked as JT_CONST, which cannot
  be good.  I added an ASSERT there for now that can be removed when
  the code has been properly tested.

mysql-test/main/cte_nonrecursive.result

@@ -183,7 +183,7 @@ where c in (select c from (select count(*) as c from t1
 where b >= 'c' group by a) as t);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	4	Using where
-1	PRIMARY	<derived3>	ref	key0	key0	8	test.t2.c	2	Using where; FirstMatch(t2)
+1	PRIMARY	<derived3>	eq_ref	distinct_key	distinct_key	8	test.t2.c	1	Using where
 3	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	8	Using where; Using temporary; Using filesort
 # two references to t specified by a query
 # selecting a field:  both in main query
@@ -369,7 +369,7 @@ select c as a from t2 where c < 4)
 select * from t2,t where t2.c=t.a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	4	Using where
-1	PRIMARY	<derived2>	ref	key0	key0	5	test.t2.c	1	
+1	PRIMARY	<derived2>	eq_ref	distinct_key	distinct_key	5	test.t2.c	1	
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
 3	UNION	t2	ALL	NULL	NULL	NULL	NULL	4	Using where
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
@@ -381,7 +381,7 @@ select c as a from t2 where c < 4) as t
 where t2.c=t.a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	4	Using where
-1	PRIMARY	<derived2>	ref	key0	key0	5	test.t2.c	1	
+1	PRIMARY	<derived2>	eq_ref	distinct_key	distinct_key	5	test.t2.c	1	
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	8	Using where
 3	UNION	t2	ALL	NULL	NULL	NULL	NULL	4	Using where
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	

mysql-test/main/derived.result

@@ -370,6 +370,15 @@ a
 2
 3
 3
+set @save2_derived_optimizer_switch_bug=@@optimizer_switch;
+set @@optimizer_switch=default;
+select * from (select * from t1 union distinct select * from t2 union all select * from t3) X;
+a
+1
+2
+3
+3
+set @@optimizer_switch=@save2_derived_optimizer_switch_bug;
 drop table t1, t2, t3;
 create table t1 (a int);
 create table t2 (a int);
@@ -1290,7 +1299,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_f
 analyze select * from t1 , ( (select t2.a from t2 order by c) union  (select t2.a from t2 order by c))q  where t1.a=q.a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	r_rows	filtered	r_filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	6	6.00	100.00	100.00	Using where
-1	PRIMARY	<derived2>	ref	key0	key0	5	test.t1.a	1	1.00	100.00	100.00	
+1	PRIMARY	<derived2>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	1.00	100.00	100.00	
 2	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	6	6.00	100.00	100.00	
 3	UNION	t2	ALL	NULL	NULL	NULL	NULL	6	6.00	100.00	100.00	
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	6.00	NULL	NULL	
@@ -1333,3 +1342,66 @@ DROP TABLE t1;
 #
 # End of 10.3 tests
 #
+#
+# Test of "Derived tables and union can now create distinct keys"
+#
+create table t1 (a int);
+insert into t1 values (100),(100);
+create table duplicates_tbl (a int);
+insert into duplicates_tbl select seq/100 from seq_1_to_10000;
+explain
+select
+t1.a IN ( SELECT COUNT(*)
+from (select a
+from duplicates_tbl
+limit 10000
+) T
+where T.a=5
+) as 'A'
+from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	MATERIALIZED	<derived3>	ALL	NULL	NULL	NULL	NULL	10000	Using where
+3	DERIVED	duplicates_tbl	ALL	NULL	NULL	NULL	NULL	10000	
+select
+t1.a IN ( SELECT COUNT(*)
+from (select a
+from duplicates_tbl
+limit 10000
+) T
+where T.a=5
+) as 'A'
+from t1;
+A
+1
+1
+explain
+select
+t1.a = all ( SELECT COUNT(*)
+from (select a
+from duplicates_tbl
+limit 10000
+) T
+where T.a=5
+) as 'A'
+from t1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	DEPENDENT SUBQUERY	<derived3>	ALL	NULL	NULL	NULL	NULL	10000	Using where
+3	DERIVED	duplicates_tbl	ALL	NULL	NULL	NULL	NULL	10000	
+select
+t1.a = all ( SELECT COUNT(*)
+from (select a
+from duplicates_tbl
+limit 10000
+) T
+where T.a=5
+) as 'A'
+from t1;
+A
+1
+1
+drop table t1, duplicates_tbl;
+#
+# End of 11.0 tests
+#

mysql-test/main/derived.test

@@ -260,6 +260,10 @@ insert into t2 values(2),(2);
 insert into t3 values(3),(3);
 select * from t1 union distinct select * from t2 union all select * from t3;
 select * from (select * from t1 union distinct select * from t2 union all select * from t3) X;
+set @save2_derived_optimizer_switch_bug=@@optimizer_switch;
+set @@optimizer_switch=default;
+select * from (select * from t1 union distinct select * from t2 union all select * from t3) X;
+set @@optimizer_switch=@save2_derived_optimizer_switch_bug;
 drop table t1, t2, t3;
 
 #
@@ -1128,7 +1132,6 @@ select * from t1 , ( (select t2.a from t2 order by c) union all (select  t2.a fr
 
 drop table t1,t2,t3;
 
-
 --echo #
 --echo # MDEV-16549: Server crashes in Item_field::fix_fields on query with
 --echo # view and subquery, Assertion `context' failed, Assertion `field' failed
@@ -1147,3 +1150,61 @@ DROP TABLE t1;
 --echo #
 --echo # End of 10.3 tests
 --echo #
+
+--echo #
+--echo # Test of "Derived tables and union can now create distinct keys"
+--echo #
+
+create table t1 (a int);
+insert into t1 values (100),(100);
+
+create table duplicates_tbl (a int);
+insert into duplicates_tbl select seq/100 from seq_1_to_10000;
+
+explain
+select
+  t1.a IN ( SELECT COUNT(*)
+              from (select a
+                    from duplicates_tbl
+                    limit 10000
+                   ) T
+              where T.a=5
+            ) as 'A'
+from t1;
+
+select
+  t1.a IN ( SELECT COUNT(*)
+              from (select a
+                    from duplicates_tbl
+                    limit 10000
+                   ) T
+              where T.a=5
+            ) as 'A'
+from t1;
+
+explain
+select
+  t1.a = all ( SELECT COUNT(*)
+              from (select a
+                    from duplicates_tbl
+                    limit 10000
+                   ) T
+              where T.a=5
+            ) as 'A'
+from t1;
+
+select
+  t1.a = all ( SELECT COUNT(*)
+              from (select a
+                    from duplicates_tbl
+                    limit 10000
+                   ) T
+              where T.a=5
+            ) as 'A'
+from t1;
+
+drop table t1, duplicates_tbl;
+
+--echo #
+--echo # End of 11.0 tests
+--echo #

mysql-test/main/derived_cond_pushdown.result

@@ -10433,7 +10433,7 @@ WHERE d_tab.e>1
 ;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	Using where
-1	PRIMARY	<derived3>	ref	key0	key0	10	test.t1.a,test.t1.b	2	FirstMatch(t1)
+1	PRIMARY	<derived3>	eq_ref	distinct_key	distinct_key	10	test.t1.a,test.t1.b	1	
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	5	Using where; Using temporary; Using filesort
 EXPLAIN FORMAT=JSON SELECT * FROM t1
 WHERE (t1.a,t1.b) IN
@@ -10465,15 +10465,14 @@ EXPLAIN
       {
         "table": {
           "table_name": "<derived3>",
-          "access_type": "ref",
-          "possible_keys": ["key0"],
-          "key": "key0",
+          "access_type": "eq_ref",
+          "possible_keys": ["distinct_key"],
+          "key": "distinct_key",
           "key_length": "10",
           "used_key_parts": ["e", "max_f"],
           "ref": ["test.t1.a", "test.t1.b"],
-          "rows": 2,
+          "rows": 1,
           "filtered": 100,
-          "first_match": "t1",
           "materialized": {
             "query_block": {
               "select_id": 3,
@@ -10532,7 +10531,7 @@ WHERE d_tab.max_f<25
 ;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	5	Using where
-1	PRIMARY	<derived3>	ref	key0	key0	10	test.t1.a,test.t1.b	2	FirstMatch(t1)
+1	PRIMARY	<derived3>	eq_ref	distinct_key	distinct_key	10	test.t1.a,test.t1.b	1	
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	5	Using temporary; Using filesort
 EXPLAIN FORMAT=JSON SELECT * FROM t1
 WHERE (t1.a,t1.b) IN
@@ -10564,15 +10563,14 @@ EXPLAIN
       {
         "table": {
           "table_name": "<derived3>",
-          "access_type": "ref",
-          "possible_keys": ["key0"],
-          "key": "key0",
+          "access_type": "eq_ref",
+          "possible_keys": ["distinct_key"],
+          "key": "distinct_key",
           "key_length": "10",
           "used_key_parts": ["e", "max_f"],
           "ref": ["test.t1.a", "test.t1.b"],
-          "rows": 2,
+          "rows": 1,
           "filtered": 100,
-          "first_match": "t1",
           "materialized": {
             "query_block": {
               "select_id": 3,
@@ -13399,7 +13397,7 @@ where
 ((d1.a<4) and (d1.c<200)));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	9	Using where
-1	PRIMARY	<derived2>	ref	key0	key0	5	test.t2.b	2	Using where
+1	PRIMARY	<derived2>	ref	key1	key1	5	test.t2.b	2	Using where
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	18	Using where; Using temporary; Using filesort
 3	INTERSECT	t1	ALL	NULL	NULL	NULL	NULL	18	Using where; Using temporary; Using filesort
 NULL	INTERSECT RESULT	<intersect2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
@@ -13432,8 +13430,8 @@ EXPLAIN
         "table": {
           "table_name": "<derived2>",
           "access_type": "ref",
-          "possible_keys": ["key0"],
-          "key": "key0",
+          "possible_keys": ["key1"],
+          "key": "key1",
           "key_length": "5",
           "used_key_parts": ["b"],
           "ref": ["test.t2.b"],
@@ -14446,7 +14444,7 @@ where
 ((d1.a>4) and (d1.c>500)));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	9	Using where
-1	PRIMARY	<derived2>	ref	key0	key0	5	test.t2.b	2	Using where
+1	PRIMARY	<derived2>	ref	key1	key1	5	test.t2.b	2	Using where
 2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	18	Using where; Using temporary; Using filesort
 3	EXCEPT	t1	ALL	NULL	NULL	NULL	NULL	18	Using where; Using temporary; Using filesort
 NULL	EXCEPT RESULT	<except2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
@@ -14479,8 +14477,8 @@ EXPLAIN
         "table": {
           "table_name": "<derived2>",
           "access_type": "ref",
-          "possible_keys": ["key0"],
-          "key": "key0",
+          "possible_keys": ["key1"],
+          "key": "key1",
           "key_length": "5",
           "used_key_parts": ["b"],
           "ref": ["test.t2.b"],
@@ -19543,7 +19541,7 @@ on (t1.id = t2.ro_id AND t2.flag = 1)
 group by t1.id) dt);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	PRIMARY	NULL	NULL	NULL	20	100.00	
-1	PRIMARY	<derived3>	ref	key0	key0	4	test.t1.id	2	100.00	FirstMatch(t1)
+1	PRIMARY	<derived3>	ref	key1	key1	4	test.t1.id	2	100.00	FirstMatch(t1)
 3	DERIVED	t1	ALL	PRIMARY	NULL	NULL	NULL	20	100.00	Using temporary; Using filesort
 3	DERIVED	t2	ref	ro_id	ro_id	4	test.t1.id	1	100.00	Using where
 Warnings:

mysql-test/main/derived_opt.result

@@ -323,10 +323,9 @@ JOIN t1 AS tc ON (tb.pk = tc.pk)
 JOIN t4 AS td ON tc.a = td.a) tu)
 limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	#	
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	#	
 1	PRIMARY	tx	eq_ref	PRIMARY	PRIMARY	4	tu.pk	#	Using index
 1	PRIMARY	ty	eq_ref	PRIMARY	PRIMARY	4	tu.pk	#	Using index
-2	MATERIALIZED	<derived3>	ALL	NULL	NULL	NULL	NULL	#	
 3	DERIVED	td	system	PRIMARY	NULL	NULL	NULL	#	Using temporary
 3	DERIVED	tc	ref	PRIMARY,a	a	3	const	#	
 3	DERIVED	ta	eq_ref	PRIMARY	PRIMARY	4	test.tc.pk	#	Using index

mysql-test/main/myisam_explain_non_select_all.result

@@ -3069,14 +3069,14 @@ Warning	1287	'<select expression> INTO <destination>;' is deprecated and will be
 EXPLAIN UPDATE        t1 SET a = 10 WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
-2	DEPENDENT SUBQUERY	<derived3>	index_subquery	key0	key0	5	func	2	
+2	DEPENDENT SUBQUERY	<derived3>	unique_subquery	distinct_key	distinct_key	5	func	1	
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	Using filesort
 FLUSH STATUS;
 FLUSH TABLES;
 EXPLAIN EXTENDED UPDATE        t1 SET a = 10 WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-2	DEPENDENT SUBQUERY	<derived3>	index_subquery	key0	key0	5	func	2	100.00	
+2	DEPENDENT SUBQUERY	<derived3>	unique_subquery	distinct_key	distinct_key	5	func	1	100.00	
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using filesort
 # Status of EXPLAIN EXTENDED query
 Variable_name	Value
@@ -3086,10 +3086,10 @@ FLUSH TABLES;
 EXPLAIN EXTENDED SELECT * FROM t1            WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-1	PRIMARY	<derived3>	ref	key0	key0	5	test.t1.a	2	100.00	FirstMatch(t1)
+1	PRIMARY	<derived3>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	100.00	
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using filesort
 Warnings:
-Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` semi join ((/* select#3 */ select `test`.`t2`.`b` AS `b` from `test`.`t2` order by `test`.`t2`.`b` limit 2,2) `x`) where `x`.`b` = `test`.`t1`.`a`
+Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a` from (/* select#3 */ select `test`.`t2`.`b` AS `b` from `test`.`t2` order by `test`.`t2`.`b` limit 2,2) `x` join `test`.`t1` where `x`.`b` = `test`.`t1`.`a`
 # Status of EXPLAIN EXTENDED "equivalent" SELECT query execution
 Variable_name	Value
 Handler_read_key	4
@@ -3120,7 +3120,7 @@ Warning	1287	'<select expression> INTO <destination>;' is deprecated and will be
 EXPLAIN UPDATE        t1, t2 SET a = 10 WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
-1	PRIMARY	<derived3>	ref	key0	key0	5	test.t1.a	2	FirstMatch(t1)
+1	PRIMARY	<derived3>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	Using filesort
 FLUSH STATUS;
@@ -3128,7 +3128,7 @@ FLUSH TABLES;
 EXPLAIN EXTENDED UPDATE        t1, t2 SET a = 10 WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-1	PRIMARY	<derived3>	ref	key0	key0	5	test.t1.a	2	100.00	FirstMatch(t1)
+1	PRIMARY	<derived3>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	100.00	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using filesort
 # Status of EXPLAIN EXTENDED query
@@ -3139,11 +3139,11 @@ FLUSH TABLES;
 EXPLAIN EXTENDED SELECT * FROM t1, t2            WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-1	PRIMARY	<derived3>	ref	key0	key0	5	test.t1.a	2	100.00	FirstMatch(t1)
+1	PRIMARY	<derived3>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	100.00	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using join buffer (flat, BNL join)
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using filesort
 Warnings:
-Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` semi join ((/* select#3 */ select `test`.`t2`.`b` AS `b` from `test`.`t2` order by `test`.`t2`.`b` limit 2,2) `x`) join `test`.`t2` where `x`.`b` = `test`.`t1`.`a`
+Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a`,`test`.`t2`.`b` AS `b` from (/* select#3 */ select `test`.`t2`.`b` AS `b` from `test`.`t2` order by `test`.`t2`.`b` limit 2,2) `x` join `test`.`t1` join `test`.`t2` where `x`.`b` = `test`.`t1`.`a`
 # Status of EXPLAIN EXTENDED "equivalent" SELECT query execution
 Variable_name	Value
 Handler_read_key	4
@@ -3173,7 +3173,7 @@ Warning	1287	'<select expression> INTO <destination>;' is deprecated and will be
 EXPLAIN UPDATE        t1, (SELECT * FROM t2) y SET a = 10 WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
-1	PRIMARY	<derived4>	ref	key0	key0	5	test.t1.a	2	FirstMatch(t1)
+1	PRIMARY	<derived4>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	
 1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	3	
 4	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	Using filesort
 2	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	
@@ -3182,7 +3182,7 @@ FLUSH TABLES;
 EXPLAIN EXTENDED UPDATE        t1, (SELECT * FROM t2) y SET a = 10 WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-1	PRIMARY	<derived4>	ref	key0	key0	5	test.t1.a	2	100.00	FirstMatch(t1)
+1	PRIMARY	<derived4>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	100.00	
 1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	3	100.00	
 4	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using filesort
 2	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	
@@ -3194,11 +3194,11 @@ FLUSH TABLES;
 EXPLAIN EXTENDED SELECT * FROM t1, (SELECT * FROM t2) y            WHERE a IN (SELECT * FROM (SELECT b FROM t2 ORDER BY b LIMIT 2,2) x);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
-1	PRIMARY	<derived4>	ref	key0	key0	5	test.t1.a	2	100.00	FirstMatch(t1)
+1	PRIMARY	<derived4>	eq_ref	distinct_key	distinct_key	5	test.t1.a	1	100.00	
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using join buffer (flat, BNL join)
 4	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using filesort
 Warnings:
-Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` semi join ((/* select#4 */ select `test`.`t2`.`b` AS `b` from `test`.`t2` order by `test`.`t2`.`b` limit 2,2) `x`) join `test`.`t2` where `x`.`b` = `test`.`t1`.`a`
+Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a`,`test`.`t2`.`b` AS `b` from (/* select#4 */ select `test`.`t2`.`b` AS `b` from `test`.`t2` order by `test`.`t2`.`b` limit 2,2) `x` join `test`.`t1` join `test`.`t2` where `x`.`b` = `test`.`t1`.`a`
 # Status of EXPLAIN EXTENDED "equivalent" SELECT query execution
 Variable_name	Value
 Handler_read_key	4

mysql-test/main/opt_trace.result

@@ -11406,7 +11406,7 @@ set in_predicate_conversion_threshold=3;
 explain select * from t0 where a in (1,2,3,4,5,6);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t0	ALL	NULL	NULL	NULL	NULL	10	Using where
-1	PRIMARY	<derived3>	ref	key0	key0	4	test.t0.a	2	FirstMatch(t0)
+1	PRIMARY	<derived3>	eq_ref	distinct_key	distinct_key	4	test.t0.a	1	
 3	DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 select json_detailed(json_extract(trace, '$**.in_to_subquery_conversion'))
 from information_schema.optimizer_trace;

mysql-test/main/opt_tvc.test

@@ -54,6 +54,23 @@ eval $optimized_query;
 eval explain extended $query;
 eval explain extended $optimized_query;
 
+
+let $query= select * from t1 where a in (1,2,2,2,3,4,5,6,7);
+
+let $optimized_query=
+select * from t1
+where a in
+      (
+        select *
+        from (values (1),(2),(2),(2),(2),(3),(4),(5),(6),(7)) as tvc_0
+      );
+
+eval $query;
+eval $optimized_query;
+eval explain extended $query;
+eval explain extended $optimized_query;
+
+
 --echo # AND-condition with IN-predicates in WHERE-part
 
 let $query=

mysql-test/main/set_operation.result

@@ -221,7 +221,7 @@ NULL	UNIT RESULT	<unit8,9,12>	ALL	NULL	NULL	NULL	NULL	NULL	NULL
 16	EXCEPT	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNIT RESULT	<unit1,15,16>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	/* select#1 */ select `__14`.`1` AS `1` from (/* select#8 */ select `__7`.`1` AS `1` from (/* select#2 */ select 1 AS `1` except /* select#3 */ select 5 AS `5` union /* select#4 */ select 6 AS `6`) `__7` union /* select#9 */ select `__8`.`2` AS `2` from (/* select#5 */ select 2 AS `2` intersect /* select#6 */ select 3 AS `3` intersect /* select#7 */ select 4 AS `4`) `__8` except /* select#12 */ select `__11`.`7` AS `7` from (/* select#10 */ select 7 AS `7` intersect /* select#11 */ select 8 AS `8`) `__11`) `__14` union all /* select#15 */ select `__15`.`9` AS `9` from (/* select#13 */ select 9 AS `9` union all /* select#14 */ select 10 AS `10`) `__15` except all /* select#16 */ select 11 AS `11`
+Note	1003	/* select#1 */ select `__14`.`1` AS `1` from (/* select#8 */ select `__7`.`1` AS `1` from (/* select#2 */ select 1 AS `1` except /* select#3 */ select 5 AS `5` union all /* select#4 */ select 6 AS `6`) `__7` union /* select#9 */ select `__8`.`2` AS `2` from (/* select#5 */ select 2 AS `2` intersect /* select#6 */ select 3 AS `3` intersect /* select#7 */ select 4 AS `4`) `__8` except /* select#12 */ select `__11`.`7` AS `7` from (/* select#10 */ select 7 AS `7` intersect /* select#11 */ select 8 AS `8`) `__11`) `__14` union all /* select#15 */ select `__15`.`9` AS `9` from (/* select#13 */ select 9 AS `9` union all /* select#14 */ select 10 AS `10`) `__15` except all /* select#16 */ select 11 AS `11`
 (select 1 union all select 2)
 union
 (select 3 union all select 4);
@@ -242,7 +242,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 5	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	UNION RESULT	<union1,6>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	/* select#1 */ select `__5`.`1` AS `1` from (/* select#2 */ select 1 AS `1` union /* select#3 */ select 2 AS `2`) `__5` union /* select#6 */ select `__6`.`3` AS `3` from (/* select#4 */ select 3 AS `3` union /* select#5 */ select 4 AS `4`) `__6`
+Note	1003	/* select#1 */ select `__5`.`1` AS `1` from (/* select#2 */ select 1 AS `1` union all /* select#3 */ select 2 AS `2`) `__5` union /* select#6 */ select `__6`.`3` AS `3` from (/* select#4 */ select 3 AS `3` union /* select#5 */ select 4 AS `4`) `__6`
 (select 1 intersect all select 2)
 except
 select 3;
@@ -258,7 +258,7 @@ NULL	INTERSECT RESULT	<intersect2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL
 4	EXCEPT	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
 NULL	EXCEPT RESULT	<except1,4>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	/* select#1 */ select `__4`.`1` AS `1` from (/* select#2 */ select 1 AS `1` intersect /* select#3 */ select 2 AS `2`) `__4` except /* select#4 */ select 3 AS `3`
+Note	1003	/* select#1 */ select `__4`.`1` AS `1` from (/* select#2 */ select 1 AS `1` intersect all /* select#3 */ select 2 AS `2`) `__4` except /* select#4 */ select 3 AS `3`
 (select 1 intersect all select 2 intersect all select 3)
 intersect
 (select 4 intersect all select 5);
@@ -278,7 +278,7 @@ NULL	INTERSECT RESULT	<intersect2,3,4>	ALL	NULL	NULL	NULL	NULL	NULL	NULL
 NULL	INTERSECT RESULT	<intersect5,6>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 NULL	INTERSECT RESULT	<intersect1,7>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	/* select#1 */ select `__6`.`1` AS `1` from (/* select#2 */ select 1 AS `1` intersect /* select#3 */ select 2 AS `2` intersect /* select#4 */ select 3 AS `3`) `__6` intersect /* select#7 */ select `__7`.`4` AS `4` from (/* select#5 */ select 4 AS `4` intersect /* select#6 */ select 5 AS `5`) `__7`
+Note	1003	/* select#1 */ select `__6`.`1` AS `1` from (/* select#2 */ select 1 AS `1` intersect all /* select#3 */ select 2 AS `2` intersect all /* select#4 */ select 3 AS `3`) `__6` intersect /* select#7 */ select `__7`.`4` AS `4` from (/* select#5 */ select 4 AS `4` intersect /* select#6 */ select 5 AS `5`) `__7`
 # test set operations with table value constructor
 (values (1,1),(1,1),(1,1),(2,2),(2,2),(3,3),(9,9))
 INTERSECT ALL

mysql-test/main/table_value_constr.test

@@ -1575,6 +1575,9 @@ values ((values (4)), (select 5)), ((select 2), (values (8)));
 
 values ((values (1) union values (1)));
 
+--error ER_SUBQUERY_NO_1_ROW
+values ((values (1) union all values (1)));
+
 values ((values (1) union values (1) union values (1)));
 
 values ((values ((values (4)))));

mysql-test/main/union.result

@@ -2783,3 +2783,70 @@ drop table t1;
 #
 # End of 10.3 tests
 #
+
+# check union all & union disctinct
+
+select 1 as res union select 2 union select 1 union select 2;
+res
+1
+2
+select 1 as res union distinct select 2 union distinct select 1 union distinct select 2;
+res
+1
+2
+select 1 as res union all select 2 union all select 1 union all select 2;
+res
+1
+2
+1
+2
+select truncate(seq/2,0)+1 as res from seq_1_to_6 union select 2;
+res
+1
+2
+3
+4
+select truncate(seq/2,0)+1 as res from seq_1_to_6 union distinct select 2;
+res
+1
+2
+3
+4
+select truncate(seq/2,0)+1 as res from seq_1_to_6 union all select 2;
+res
+1
+2
+2
+3
+3
+4
+2
+select 1 as res union all select 2 union distinct select 1 union all select 2;
+res
+1
+2
+2
+select 1 as res union select 2 union all select 1 union distinct select 3;
+res
+1
+2
+3
+select 1 as res union select 2 union all select 1 union distinct select 3 union all select 2;
+res
+1
+2
+3
+2
+select 1 as res union select 2 union all select 1 union distinct select 3 union all select 2 union distinct select 5;
+res
+1
+2
+3
+5
+select truncate(seq/2,0)+1 as res from seq_1_to_6 union all select 2 union all select 1 union distinct select 3 union all select 2;
+res
+1
+2
+3
+4
+2

mysql-test/main/union.test

 #
 # Test of unions
 #
+--source include/have_sequence.inc
+
 
 CREATE TABLE t1 (a int not null, b char (10) not null);
 insert into t1 values(1,'a'),(2,'b'),(3,'c'),(3,'c');
@@ -2010,3 +2012,21 @@ drop table t1;
 --echo #
 --echo # End of 10.3 tests
 --echo #
+
+--echo
+--echo # check union all & union disctinct
+--echo
+
+select 1 as res union select 2 union select 1 union select 2;
+select 1 as res union distinct select 2 union distinct select 1 union distinct select 2;
+select 1 as res union all select 2 union all select 1 union all select 2;
+
+select truncate(seq/2,0)+1 as res from seq_1_to_6 union select 2;
+select truncate(seq/2,0)+1 as res from seq_1_to_6 union distinct select 2;
+select truncate(seq/2,0)+1 as res from seq_1_to_6 union all select 2;
+
+select 1 as res union all select 2 union distinct select 1 union all select 2;
+select 1 as res union select 2 union all select 1 union distinct select 3;
+select 1 as res union select 2 union all select 1 union distinct select 3 union all select 2;
+select 1 as res union select 2 union all select 1 union distinct select 3 union all select 2 union distinct select 5;
+select truncate(seq/2,0)+1 as res from seq_1_to_6 union all select 2 union all select 1 union distinct select 3 union all select 2;

mysql-test/suite/federated/federatedx_create_handlers.result

@@ -298,7 +298,7 @@ SELECT * FROM federated.t1 WHERE id >= 5) t
 WHERE federated.t3.name=t.name;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	7	
-1	PRIMARY	<derived2>	ref	key0	key0	18	federated.t3.name	2	
+1	PRIMARY	<derived2>	ref	key1	key1	18	federated.t3.name	2	
 2	PUSHED DERIVED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL
 #
 # MDEV-21887: federatedx crashes on SELECT ... INTO query in select_handler code

sql/item_subselect.cc

@@ -1588,8 +1588,9 @@ Item_exists_subselect::Item_exists_subselect(THD *thd,
 {
   DBUG_ENTER("Item_exists_subselect::Item_exists_subselect");
 
-
   init(select_lex, new (thd->mem_root) select_exists_subselect(thd, this));
+  select_lex->distinct= 1;
+  select_lex->master_unit()->distinct= 1;
   max_columns= UINT_MAX;
   null_value= FALSE; //can't be NULL
   base_flags&= ~item_base_t::MAYBE_NULL; //can't be NULL
@@ -1640,6 +1641,39 @@ Item_in_subselect::Item_in_subselect(THD *thd, Item * left_exp,
       Item_row(thd, static_cast<Item_row*>(left_exp));
   func= &eq_creator;
   init(select_lex, new (thd->mem_root) select_exists_subselect(thd, this));
+  select_lex->distinct= 1;
+
+  /*
+    If the IN subquery (xxx IN (SELECT ...) is a join without grouping,
+    we don't need duplicates from the tables it is joining. These
+    tables can be derived tables, like shown in the following
+    example. In this case, it's useful to indicate that we don't need
+    duplicates from them either.
+
+    Example:
+     col IN (SELECT ...   -- this is the select_lex
+              FROM
+                (SELECT ... FROM t1) AS t1, -- child1, first_inner_init().
+                (SELECT ... FROM t2) AS t2, -- child2
+              WHERE
+                ...
+            )
+
+     We don't need duplicates from either child1 or child2.
+     We only indicate this to child1 (select_lex->first_inner_unit()), as that
+     catches most of practically important use cases.
+
+     (The check for item==NULL is to make sure the subquery is a derived table
+     and not any other kind of subquery like another IN (SELECT ...) or a scalar-
+     context (SELECT 'foo'))
+  */
+
+  select_lex->master_unit()->distinct= 1;
+  if (!select_lex->with_sum_func &&
+      select_lex->first_inner_unit() &&
+      select_lex->first_inner_unit()->item == NULL)
+    select_lex->first_inner_unit()->distinct= 1;
+
   max_columns= UINT_MAX;
   set_maybe_null();
   reset();
@@ -1667,6 +1701,16 @@ Item_allany_subselect::Item_allany_subselect(THD *thd, Item * left_exp,
       Item_row(thd, static_cast<Item_row*>(left_exp));
   func= func_creator(all_arg);
   init(select_lex, new (thd->mem_root) select_exists_subselect(thd, this));
+  select_lex->distinct= 1;
+  /*
+    If this is is 'xxx IN (SELECT ...) mark that the we are only interested in
+    unique values for the select
+  */
+  select_lex->master_unit()->distinct= 1;
+  if (!select_lex->with_sum_func &&
+      select_lex->first_inner_unit() &&
+      select_lex->first_inner_unit()->item == NULL)
+    select_lex->first_inner_unit()->distinct= 1;
   max_columns= 1;
   reset();
   //if test_limit will fail then error will be reported to client

sql/sql_derived.cc

@@ -870,18 +870,20 @@ bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *derived)
     goto exit;
 
   /*
-    Temp table is created so that it hounours if UNION without ALL is to be 
+    Temp table is created so that it honors if UNION without ALL is to be
     processed
 
-    As 'distinct' parameter we always pass FALSE (0), because underlying
-    query will control distinct condition by itself. Correct test of
-    distinct underlying query will be is_unit_op &&
+    As 'distinct' parameter we pass unit->distinct, which tells us if
+    the values should be uniq.
+    Note that the underlying query will also control distinct condition.
+    Correct test of distinct underlying query will be is_unit_op &&
     !unit->union_distinct->next_select() (i.e. it is union and last distinct
     SELECT is last SELECT of UNION).
   */
   thd->create_tmp_table_for_derived= TRUE;
   if (!(derived->table) &&
-      derived->derived_result->create_result_table(thd, &unit->types, FALSE,
+      derived->derived_result->create_result_table(thd, &unit->types,
+                                                   unit->distinct,
                                                    (first_select->options |
                                                    thd->variables.option_bits |
                                                    TMP_TABLE_ALL_COLUMNS),

sql/sql_lex.cc

@@ -2873,7 +2873,7 @@ void st_select_lex_node::init_query_common()
 {
   options= 0;
   set_linkage(UNSPECIFIED_TYPE);
-  distinct= TRUE;
+  distinct= FALSE;
   no_table_names_allowed= 0;
   uncacheable= 0;
 }
@@ -10146,6 +10146,7 @@ SELECT_LEX_UNIT *LEX::parsed_select_expr_start(SELECT_LEX *s1, SELECT_LEX *s2,
   if (res == NULL)
     return NULL;
   res->pre_last_parse= sel1;
+  res->distinct= distinct;
   push_select(res->fake_select_lex);
   return res;
 }
@@ -10392,7 +10393,6 @@ bool LEX::parsed_TVC_start()
   insert_list= 0;
   if (!(sel= alloc_select(TRUE)) || push_select(sel))
     return true;
-  sel->init_select();
   sel->braces= FALSE; // just initialisation
   return false;
 }

sql/sql_select.cc

@@ -2613,8 +2613,12 @@ int JOIN::optimize_stage2()
   if (select_lex->handle_derived(thd->lex, DT_OPTIMIZE))
     DBUG_RETURN(1);
 
-  if (optimizer_flag(thd, OPTIMIZER_SWITCH_DERIVED_WITH_KEYS))
-    drop_unused_derived_keys();
+  /*
+    We have to call drop_unused_derived_keys() even if we don't have any
+    generated keys (enabled with OPTIMIZER_SWITCH_DERIVED_WITH_KEYS)
+    as we may still have unique constraints we have to get rid of.
+  */
+  drop_unused_derived_keys();
 
   if (rollup.state != ROLLUP::STATE_NONE)
   {
@@ -5698,7 +5702,14 @@ make_join_statistics(JOIN *join, List<TABLE_LIST> &tables_list,
             base_const_ref.intersect(base_part);
             base_eq_part= eq_part;
             base_eq_part.intersect(base_part);
-            if (table->actual_key_flags(keyinfo) & HA_NOSAME)
+
+            /*
+              We can read the const record if we are using a full unique key and
+              if the table is not an unopened to be materialized table/view.
+            */
+            if ((table->actual_key_flags(keyinfo) & HA_NOSAME) &&
+                (!s->table->pos_in_table_list->is_materialized_derived() ||
+                 s->table->pos_in_table_list->fill_me))
             {
               
 	      if (base_const_ref == base_eq_part &&
@@ -13573,9 +13584,12 @@ void JOIN::drop_unused_derived_keys()
       if (tab->ref.key >= 0 && tab->ref.key < MAX_KEY)
         tab->ref.key= 0;
       else
+      {
         tmp_tbl->s->keys= 0;
+        tmp_tbl->s->uniques= 0;
+      }
     }
-    tab->keys= (key_map) (tmp_tbl->s->keys ? 1 : 0);
+    tab->keys= (key_map) (tmp_tbl->s->keys || tmp_tbl->s->uniques ? 1 : 0);
   }
 }
 
@@ -22708,12 +22722,16 @@ join_read_const_table(THD *thd, JOIN_TAB *tab, POSITION *pos)
   if (tab->table->pos_in_table_list->is_materialized_derived() &&
       !tab->table->pos_in_table_list->fill_me)
   {
+    DBUG_ASSERT(0);
     //TODO: don't get here at all
-    /* Skip materialized derived tables/views. */
+    /*
+      Skip materialized derived tables/views as they temporary table is not
+      opened yet.
+    */
     DBUG_RETURN(0);
   }
-  else if (tab->table->pos_in_table_list->jtbm_subselect && 
-          tab->table->pos_in_table_list->jtbm_subselect->is_jtbm_const_tab)
+  else if (tab->table->pos_in_table_list->jtbm_subselect &&
+           tab->table->pos_in_table_list->jtbm_subselect->is_jtbm_const_tab)
   {
     /* Row will not be found */
     int res;

sql/sql_tvc.cc

@@ -705,11 +705,11 @@ st_select_lex *wrap_tvc(THD *thd, st_select_lex *tvc_sl,
     goto err;
   wrapper_sl->select_number= ++thd->lex->stmt_lex->current_select_number;
   wrapper_sl->parent_lex= lex; /* Used in init_query. */
-  wrapper_sl->init_query();
-  wrapper_sl->init_select();
+  wrapper_sl->make_empty_select();
 
   wrapper_sl->nest_level= tvc_sl->nest_level;
   wrapper_sl->parsing_place= tvc_sl->parsing_place;
+  wrapper_sl->distinct=      tvc_sl->distinct;
   wrapper_sl->set_linkage(tvc_sl->get_linkage());
   wrapper_sl->exclude_from_table_unique_test=
                                  tvc_sl->exclude_from_table_unique_test;
@@ -737,6 +737,7 @@ st_select_lex *wrap_tvc(THD *thd, st_select_lex *tvc_sl,
   derived_unit->init_query();
   derived_unit->thd= thd;
   derived_unit->include_down(wrapper_sl);
+  derived_unit->distinct= tvc_sl->distinct;
 
   /*
     Attach the select used of TVC as the only slave to the unit for
@@ -1011,7 +1012,9 @@ Item *Item_func_in::in_predicate_to_in_subs_transformer(THD *thd,
   lex->init_select();
   tvc_select= lex->current_select;
   derived_unit= tvc_select->master_unit();
+  derived_unit->distinct= 1;
   tvc_select->set_linkage(DERIVED_TABLE_TYPE);
+  tvc_select->distinct= 1;
 
   /* Create TVC used in the transformation */
   if (create_value_list_for_tvc(thd, &values))

sql/sql_union.cc

@@ -1302,6 +1302,7 @@ bool st_select_lex_unit::prepare(TABLE_LIST *derived_arg,
   bool instantiate_tmp_table= false;
   bool single_tvc= !first_sl->next_select() && first_sl->tvc;
   bool single_tvc_wo_order= single_tvc && !first_sl->order_list.elements;
+  bool distinct_key= 0;
   DBUG_ENTER("st_select_lex_unit::prepare");
   DBUG_ASSERT(thd == current_thd);
 
@@ -1405,15 +1406,17 @@ bool st_select_lex_unit::prepare(TABLE_LIST *derived_arg,
     {
     case INTERSECT_TYPE:
       have_intersect= TRUE;
-      if (!s->distinct){
-        have_except_all_or_intersect_all= true;
-      }
+      if (!s->distinct)
+        have_except_all_or_intersect_all= TRUE;
       break;
     case EXCEPT_TYPE:
       have_except= TRUE;
-      if (!s->distinct){
+      if (!s->distinct)
         have_except_all_or_intersect_all= TRUE;
-      }
+      break;
+    case DERIVED_TABLE_TYPE:
+      if (s->distinct)
+        distinct_key= 1;
       break;
     default:
       break;
@@ -1620,7 +1623,8 @@ bool st_select_lex_unit::prepare(TABLE_LIST *derived_arg,
         if (join_union_item_types(thd, types, union_part_count + 1))
           goto err;
         if (union_result->create_result_table(thd, &types,
-                                              MY_TEST(union_distinct),
+                                              (MY_TEST(union_distinct) ||
+                                               distinct_key),
                                               create_options,
                                               &derived_arg->alias, false,
                                               instantiate_tmp_table, false,
@@ -1643,7 +1647,7 @@ bool st_select_lex_unit::prepare(TABLE_LIST *derived_arg,
 
           res= derived_arg->derived_result->create_result_table(thd,
                                                             &types,
-                                                            FALSE,
+                                                            distinct_key,
                                                             create_options,
                                                             &derived_arg->alias,
                                                             FALSE, FALSE,
@@ -1767,9 +1771,9 @@ bool st_select_lex_unit::prepare(TABLE_LIST *derived_arg,
         union_result->create_result_table(thd, &types,
                                           MY_TEST(union_distinct) ||
                                             have_except_all_or_intersect_all ||
-                                            have_intersect,
-                                          create_options, &empty_clex_str, false,
-                                          instantiate_tmp_table, false,
+                                            have_intersect || distinct_key,
+                                          create_options, &empty_clex_str,
+                                          false, instantiate_tmp_table, false,
                                           hidden);
       union_result->addon_cnt= hidden;
       for (uint i= 0; i < hidden; i++)