EXPLAIN UNION using same routing which used for execution which allow return correct bug messages (Bug #3639)

EXPLAIN of hidden SELECT of UNION


mysql-test/r/derived.result:
  explain of hidden select
mysql-test/r/subselect.result:
  explain of hidden select
mysql-test/r/union.result:
  explain of hidden select
  correct error messages on explain
mysql-test/t/subselect.test:
  show eliminated costants in WHERE clause
mysql-test/t/union.test:
  correct error messages on EXPLAIN with union
sql/item.cc:
  fixed name constructing for global ORDER BY items
sql/sql_class.h:
  select ID can be negative (for hidden SELECTs)
  removed unused field
sql/sql_lex.cc:
  new flag of UNION EXPLAIN
sql/sql_lex.h:
  new flag of UNION EXPLAIN
  select ID can be negative (for hidden SELECTs)
sql/sql_select.cc:
  EXPLAIN UNION using same routing which used for execution
  explain for hidden SELECT of UNION
sql/sql_union.cc:
  EXPLAIN UNION using same routing which used for execution

1 files changed, 13 insertions, 10 deletions

diff --git a/mysql-test/r/union.result b/mysql-test/r/union.result
index bf8b8df7c65..d14c4408946 100644
--- a/mysql-test/r/union.result
+++ b/mysql-test/r/union.result
@@ -86,6 +86,7 @@ explain extended (select a,b from t1 limit 2)  union all (select a,b from t2 ord
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	
 2	UNION	t2	ALL	NULL	NULL	NULL	NULL	4	Using filesort
+-1	UNION RESULT	<union1>	ALL	NULL	NULL	NULL	NULL	NULL	Using filesort
 Warnings:
 Note	1003	(select high_priority test.t1.a AS `a`,test.t1.b AS `b` from test.t1 limit 2) union all (select test.t2.a AS `a`,test.t2.b AS `b` from test.t2 order by test.t2.a limit 1) order by b desc
 (select sql_calc_found_rows  a,b from t1 limit 2)  union all (select a,b from t2 order by a) limit 2;
@@ -106,21 +107,15 @@ explain select a,b from t1 union all select a,b from t2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	
 2	UNION	t2	ALL	NULL	NULL	NULL	NULL	4	
+-1	UNION RESULT	<union1>	ALL	NULL	NULL	NULL	NULL	NULL	
 explain select xx from t1 union select 1;
 ERROR 42S22: Unknown column 'xx' in 'field list'
 explain select a,b from t1 union select 1;
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	4	
-2	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+ERROR 21000: The used SELECT statements have a different number of columns
 explain select 1 union select a,b from t1 union select 1;
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
-2	UNION	t1	ALL	NULL	NULL	NULL	NULL	4	
-3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+ERROR 21000: The used SELECT statements have a different number of columns
 explain select a,b from t1 union select 1 limit 0;
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
-2	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+ERROR 21000: The used SELECT statements have a different number of columns
 select a,b from t1 into outfile 'skr' union select a,b from t2;
 ERROR HY000: Wrong usage of UNION and INTO
 select a,b from t1 order by a union select a,b from t2;
@@ -475,6 +470,7 @@ explain extended (select * from t1 where a=1) union (select * from t2 where a=1)
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	const	PRIMARY	PRIMARY	4	const	1	
 2	UNION	t2	const	PRIMARY	PRIMARY	4	const	1	
+-1	UNION RESULT	<union1>	ALL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
 Note	1003	(select high_priority test.t1.a AS `a`,test.t1.b AS `b` from test.t1 where (test.t1.a = 1)) union (select test.t2.a AS `a`,test.t2.b AS `b` from test.t2 where (test.t2.a = 1))
 (select * from t1 where a=5) union (select * from t2 where a=1);
@@ -497,10 +493,12 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
 2	UNION	t1	index	PRIMARY	PRIMARY	4	NULL	4	Using index
 2	UNION	t2	index	PRIMARY	PRIMARY	4	NULL	3	Using where; Using index
+-1	UNION RESULT	<union1>	ALL	NULL	NULL	NULL	NULL	NULL	
 explain (select * from t1 where a=1) union (select * from t1 where b=1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	const	PRIMARY	PRIMARY	4	const	1	
 2	UNION	t1	ref	b	b	5	const	1	Using where
+-1	UNION RESULT	<union1>	ALL	NULL	NULL	NULL	NULL	NULL	
 drop table t1,t2;
 create table t1 (   id int not null auto_increment, primary key (id)   ,user_name text );
 create table t2 (    id int not null auto_increment, primary key (id)   ,group_name text );
@@ -950,3 +948,8 @@ a
 1
 drop table t1, t2;
 set sql_select_limit=default;
+CREATE TABLE t1 (i int(11) default NULL,c char(1) default NULL,KEY i (i));
+CREATE TABLE t2 (i int(11) default NULL,c char(1) default NULL,KEY i (i));
+explain (select * from t1) union (select * from t2) order by not_existing_column;
+ERROR 42S22: Unknown column 'not_existing_column' in 'order clause'
+drop table t1, t2;