Fix for bug#23113: Different behavior on altering ENUM fields between 5.0 and 5.1

Problem: mysqld doesn't detect that enum data must be reinserted performing
'ALTER TABLE' in some cases.

Fix: reinsert data altering an enum field if enum values are changed.


mysql-test/r/alter_table.result:
  Fix for bug#23113: Different behavior on altering ENUM fields between 5.0 and 5.1
    - test result.
mysql-test/t/alter_table.test:
  Fix for bug#23113: Different behavior on altering ENUM fields between 5.0 and 5.1
    - test case.
sql/field.cc:
  Fix for bug#23113: Different behavior on altering ENUM fields between 5.0 and 5.1
    - Field_enum::is_equal() introduced, which is called to detect that a field
  is changing by 'ALTER TABLE'.
sql/field.h:
  Fix for bug#23113: Different behavior on altering ENUM fields between 5.0 and 5.1
    - Field_enum::is_equal() introduced, which is called to detect that a field
  is changing by 'ALTER TABLE'.

1 files changed, 12 insertions, 0 deletions

diff --git a/mysql-test/t/alter_table.test b/mysql-test/t/alter_table.test
index 662f9095810..c45c89095fa 100644
--- a/mysql-test/t/alter_table.test
+++ b/mysql-test/t/alter_table.test
@@ -947,4 +947,16 @@ ALTER TABLE t1 CHANGE d c varchar(10);
 --disable_info
 DROP TABLE t1;
 
+
+#
+# Bug #23113: Different behavior on altering ENUM fields between 5.0 and 5.1
+#
+CREATE TABLE t1(a INT AUTO_INCREMENT PRIMARY KEY, 
+  b ENUM('a', 'b', 'c') NOT NULL);
+INSERT INTO t1 (b) VALUES ('a'), ('c'), ('b'), ('b'), ('a');
+ALTER TABLE t1 MODIFY b ENUM('a', 'z', 'b', 'c') NOT NULL;
+SELECT * FROM t1;
+DROP TABLE t1;
+
+
 --echo End of 5.1 tests