MDEV-6289 : Unexpected results when querying information_schema

- When traversing JOIN_TABs with first_linear_tab/next_linear_tab(), don't forget
  to enter the semi-join nest when it is the first table in the join order.
  Failure to do so could cause e.g. I_S tables not to be filled.

1 files changed, 37 insertions, 0 deletions

diff --git a/mysql-test/r/subselect_mat.result b/mysql-test/r/subselect_mat.result
index a78cc1c3a9e..7eb41683dd0 100644
--- a/mysql-test/r/subselect_mat.result
+++ b/mysql-test/r/subselect_mat.result
@@ -2108,6 +2108,43 @@ EXECUTE stmt;
 a
 DROP TABLE t1, t2;
 DROP VIEW v2;
+#
+# MDEV-6289 : Unexpected results when querying information_schema
+#
+CREATE TABLE t1 (
+id int(11) unsigned NOT NULL AUTO_INCREMENT,
+db varchar(254) NOT NULL DEFAULT '',
+PRIMARY KEY (id),
+UNIQUE KEY db (db)
+) DEFAULT CHARSET=utf8;
+INSERT INTO t1 (db) VALUES ('mysqltest1'),('mysqltest2'),('mysqltest3'),('mysqltest4');
+drop database if exists mysqltest1;
+drop database if exists mysqltest2;
+drop database if exists mysqltest3;
+drop database if exists mysqltest4;
+create database mysqltest1;
+create database mysqltest2;
+create database mysqltest3;
+create database mysqltest4;
+SELECT db FROM t1 WHERE db IN (SELECT SCHEMA_NAME FROM information_schema.SCHEMATA) ORDER BY db DESC;
+db
+mysqltest4
+mysqltest3
+mysqltest2
+mysqltest1
+EXPLAIN EXTENDED
+SELECT db FROM t1 WHERE db IN (SELECT SCHEMA_NAME FROM information_schema.SCHEMATA) ORDER BY db DESC;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	<subquery2>	ALL	distinct_key	NULL	NULL	NULL	2	100.00	Using temporary; Using filesort
+1	PRIMARY	t1	eq_ref	db	db	764	information_schema.SCHEMATA.SCHEMA_NAME	1	100.00	Using where; Using index
+2	MATERIALIZED	SCHEMATA	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
+Warnings:
+Note	1003	select `test`.`t1`.`db` AS `db` from `test`.`t1` semi join (`information_schema`.`SCHEMATA`) where (`test`.`t1`.`db` = `information_schema`.`SCHEMATA`.`SCHEMA_NAME`) order by `test`.`t1`.`db` desc
+drop table t1;
+drop database mysqltest1;
+drop database mysqltest2;
+drop database mysqltest3;
+drop database mysqltest4;
 # End of 5.5 tests
 set @subselect_mat_test_optimizer_switch_value=null;
 set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';