Bug#43508: Renaming timestamp or date column triggers table copy

We set up DATE and TIMESTAMP differently in field-creation than we
did in field-MD creation (for CREATE). Admirably, ALTER TABLE
detected this and didn't damage any data, but it did initiate a
full copy/conversion, which we don't really need to do.

Now we describe Field and Create_field the same for those types.
As a result, ALTER TABLE that only changes meta-data (like a
field's name) no longer forces a data-copy when there needn't
be one.


mysql-test/r/alter_table.result:
  0 rows should be affected when a meta-data change is enough ALTER TABLE.
mysql-test/t/alter_table.test:
  add test-case: show that we don't do a full data-copy on ALTER TABLE
  when we don't need to.
sql/field.cc:
  Remove Field_str::compare_str_field_flags() (now in Field/Create_field as
  field_flags_are_binary().
  
  Correct some field-lengths!
sql/field.h:
  Clean-up: use defined constants rather than numeric literals for certain
  field-lengths.
  
  Add enquiry-functions binaryp() to classes Field and Create_field.
  This replaces field.cc's Field_str::compare_str_field_flags().

1 files changed, 15 insertions, 0 deletions

diff --git a/mysql-test/t/alter_table.test b/mysql-test/t/alter_table.test
index ae48d5a8736..6f36a8a02b5 100644
--- a/mysql-test/t/alter_table.test
+++ b/mysql-test/t/alter_table.test
@@ -1000,4 +1000,19 @@ ALTER TABLE t1 MODIFY b ENUM('a', 'z', 'b', 'c') NOT NULL;
 SELECT * FROM t1;
 DROP TABLE t1;
 
+#
+# Bug#43508: Renaming timestamp or date column triggers table copy
+#
+
+CREATE TABLE t1 (f1 TIMESTAMP NULL DEFAULT NULL,
+                 f2 INT(11) DEFAULT NULL) ENGINE=MYISAM DEFAULT CHARSET=utf8;
+
+INSERT INTO t1 VALUES (NULL, NULL), ("2009-10-09 11:46:19", 2);
+
+--echo this should affect no rows as there is no real change
+--enable_info
+ALTER TABLE t1 CHANGE COLUMN f1 f1_no_real_change TIMESTAMP NULL DEFAULT NULL;
+--disable_info
+DROP TABLE t1;
+
 --echo End of 5.1 tests