1 files changed, 39 insertions, 0 deletions
diff --git a/mysql-test/t/windows.test b/mysql-test/t/windows.test
index d6bcfeb8cb3..79517df6517 100644
--- a/mysql-test/t/windows.test
+++ b/mysql-test/t/windows.test
@@ -18,3 +18,42 @@ create table nu (a int);
 drop table nu;
 
 # End of 4.1 tests
+
+#
+# Bug #20789: Merge Subtable Rename Causes Crash
+#
+CREATE TABLE `t1` (
+  `TIM` datetime NOT NULL,
+  `VAL` double default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+CREATE TABLE `t2` (
+  `TIM` datetime NOT NULL,
+  `VAL` double default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1;
+CREATE TABLE `mt` (
+  `TIM` datetime NOT NULL,
+  `VAL` double default NULL
+) ENGINE=MRG_MyISAM DEFAULT CHARSET=latin1 INSERT_METHOD=LAST
+UNION=(`t1`,`t2`);
+
+# insert into the merge table and thus open it.
+INSERT INTO mt VALUES ('2006-01-01',0);
+
+# Alter one of the tables that are part of the merge table
+ALTER TABLE `t2` RENAME TO `t`;
+
+# Insert into the merge table that has just been altered
+--error 1015
+INSERT INTO mt VALUES ('2006-01-01',0); 
+--error 1015
+select * from mt;
+
+FLUSH TABLES;
+--error 1017
+select * from mt;
+
+# Alter one of the tables that are part of the merge table
+ALTER TABLE `t` RENAME TO `t2`;
+INSERT INTO mt VALUES ('2006-01-01',0);
+select * from mt; 
+