Commit 8838c971 authored by unknown's avatar unknown
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A fix (Bug #4980: union statement with () union () order by produces wrong explain).

parent b871ea38

mysql-test/r/union.result

+8 −1
Original line number Diff line number Diff line
@@ -88,7 +88,6 @@ explain (select a,b from t1 limit 2) union all (select a,b from t2 order by a l 
table	type	possible_keys	key	key_len	ref	rows	Extra

t1	ALL	NULL	NULL	NULL	NULL	4	

t2	ALL	NULL	NULL	NULL	NULL	4	Using filesort

t1	ALL	NULL	NULL	NULL	NULL	4	

(select sql_calc_found_rows  a,b from t1 limit 2)  union all (select a,b from t2 order by a) limit 2;

a	b

1	a
@@ -424,8 +423,16 @@ create table t1 select a from t1 union select a from t2; 
INSERT TABLE 't1' isn't allowed in FROM table list

select a from t1 union select a from t2 order by t2.a;

Unknown column 't2.a' in 'ORDER BY'

drop table t1;

drop table t1,t2;

select length(version()) > 1 as `*` UNION select 2;

*

1

2

create table t1 (a int);

insert into t1 values (0), (3), (1), (2);

explain (select * from t1) union (select * from t1) order by a;

table	type	possible_keys	key	key_len	ref	rows	Extra

t1	ALL	NULL	NULL	NULL	NULL	4	

t1	ALL	NULL	NULL	NULL	NULL	4	

drop table t1;

mysql-test/t/union.test

+9 −0
Original line number Diff line number Diff line
@@ -228,6 +228,7 @@ create temporary table t1 select a from t1 union select a from t2; 
create table t1 select a from t1 union select a from t2;

--error 1054

select a from t1 union select a from t2 order by t2.a;

drop table t1;   # Drop temporary table

drop table t1,t2;



#
@@ -236,3 +237,11 @@ drop table t1,t2; 


select length(version()) > 1 as `*` UNION select 2;



#

# Bug #4980: problem with explain

#



create table t1 (a int);

insert into t1 values (0), (3), (1), (2);

explain (select * from t1) union (select * from t1) order by a;

drop table t1;

sql/sql_union.cc

+4 −0
Original line number Diff line number Diff line
@@ -148,6 +148,10 @@ int mysql_union(THD *thd, LEX *lex,select_result *result) 
  {

    ha_rows records_at_start;

    lex->select=sl;

#if MYSQL_VERSION_ID < 40100

    if (describe && sl->linkage == NOT_A_SELECT)

      break;      // Skip extra item in case of 'explain'

#endif

    /* Don't use offset for the last union if there is no braces */

    if (sl != lex_sl)

    {