Bug#30302: Tables that were optimized away are printed in the

EXPLAIN EXTENDED warning.

Query optimizer searches for the constant tables and optimizes them away. This
means that fields of such tables are substituted for their values and on later
phases they are treated as constants. After this constant tables are removed
from the query execution plan. Nevertheless constant tables were shown in 
the EXPLAIN EXTENDED warning thus producing query that might be not an
equivalent of the original query.
        
Now the print_join function skips all tables that were optimized away from
printing to the EXPLAIN EXTENDED warning. If all tables were optimized away it
produces the 'FROM dual' clause.


mysql-test/r/explain.result:
  A test case added for the bug#30302.
mysql-test/r/func_default.result:
  Adjusted test case result after fix for the bug#30302.
mysql-test/r/func_regexp.result:
  Adjusted test case result after fix for the bug#30302.
mysql-test/r/func_test.result:
  Adjusted test case result after fix for the bug#30302.
mysql-test/r/having.result:
  Adjusted test case result after fix for the bug#30302.
mysql-test/r/select.result:
  Adjusted test case result after fix for the bug#30302.
mysql-test/r/subselect.result:
  Adjusted test case result after fix for the bug#30302.
mysql-test/r/subselect3.result:
  Adjusted test case result after fix for the bug#30302.
mysql-test/r/type_datetime.result:
  Adjusted test case result after fix for the bug#30302.
mysql-test/t/explain.test:
  A test case added for the bug#30302.
sql/sql_select.cc:
  Bug#30302: Tables that were optimized away are printed in the
  EXPLAIN EXTENDED warning.
  Now the print_join function skips all tables that were optimized away from
  printing to the EXPLAIN EXTENDED warning. If all tables were optimized away it
  produces the 'FROM dual' clause.
sql/table.h:
  Adjusted test case result after fix for the bug#30302.
  The optimized_away flag is added to the TABLE_LIST struct.

1 files changed, 5 insertions, 5 deletions

diff --git a/mysql-test/r/subselect.result b/mysql-test/r/subselect.result
index c60ac9790c5..fc0a933b732 100644
--- a/mysql-test/r/subselect.result
+++ b/mysql-test/r/subselect.result
@@ -50,7 +50,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 Warnings:
 Note	1276	Field or reference 'b.a' of SELECT #3 was resolved in SELECT #1
 Note	1276	Field or reference 'b.a' of SELECT #3 was resolved in SELECT #1
-Note	1003	select 1 AS `1` from (select 1 AS `a`) `b` having ((select '1' AS `a`) = 1)
+Note	1003	select 1 AS `1` from dual having ((select '1' AS `a`) = 1)
 SELECT 1 FROM (SELECT 1 as a) as b HAVING (SELECT a)=1;
 1
 1
@@ -203,7 +203,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
 2	SUBQUERY	t3	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where; Using filesort
 Warnings:
-Note	1003	select (select `test`.`t3`.`a` AS `a` from `test`.`t3` where (`test`.`t3`.`a` < 8) order by 1 desc limit 1) AS `(select t3.a from t3 where a<8 order by 1 desc limit 1)`,'2' AS `a` from (select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`a` > 1)) `tt`
+Note	1003	select (select `test`.`t3`.`a` AS `a` from `test`.`t3` where (`test`.`t3`.`a` < 8) order by 1 desc limit 1) AS `(select t3.a from t3 where a<8 order by 1 desc limit 1)`,'2' AS `a` from dual
 select * from t1 where t1.a=(select t2.a from t2 where t2.b=(select max(a) from t3) order by 1 desc limit 1);
 a
 2
@@ -314,7 +314,7 @@ NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL
 Warnings:
 Note	1276	Field or reference 'test.t2.a' of SELECT #2 was resolved in SELECT #1
 Note	1276	Field or reference 'test.t2.a' of SELECT #3 was resolved in SELECT #1
-Note	1003	select (select '2' AS `a` from `test`.`t1` where ('2' = `test`.`t2`.`a`) union select `test`.`t5`.`a` AS `a` from `test`.`t5` where (`test`.`t5`.`a` = `test`.`t2`.`a`)) AS `(select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a)`,`test`.`t2`.`a` AS `a` from `test`.`t2`
+Note	1003	select (select '2' AS `a` from dual where ('2' = `test`.`t2`.`a`) union select `test`.`t5`.`a` AS `a` from `test`.`t5` where (`test`.`t5`.`a` = `test`.`t2`.`a`)) AS `(select a from t1 where t1.a=t2.a union select a from t5 where t5.a=t2.a)`,`test`.`t2`.`a` AS `a` from `test`.`t2`
 select (select a from t1 where t1.a=t2.a union all select a from t5 where t5.a=t2.a), a from t2;
 ERROR 21000: Subquery returns more than 1 row
 create table t6 (patient_uq int, clinic_uq int, index i1 (clinic_uq));
@@ -1429,7 +1429,7 @@ explain extended (select * from t1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	100.00	
 Warnings:
-Note	1003	(select 'tttt' AS `s1` from `test`.`t1`)
+Note	1003	(select 'tttt' AS `s1` from dual)
 (select * from t1);
 s1
 tttt
@@ -1617,7 +1617,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 3	UNION	t1	system	NULL	NULL	NULL	NULL	1	100.00	
 NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	select 'e' AS `s1` from `test`.`t1` where 1
+Note	1003	select 'e' AS `s1` from dual where 1
 drop table t1;
 CREATE TABLE t1 (number char(11) NOT NULL default '') ENGINE=MyISAM CHARSET=latin1;
 INSERT INTO t1 VALUES ('69294728265'),('18621828126'),('89356874041'),('95895001874');