Bug#19371 VARBINARY() have trailing zeros after upgrade from 4.1

 - Detect if a table has field of type MYSQL_TYPE_VAR_STRING while running
   "CHECK TABLE t FOR UPGRADE" and indicate it need to be fixed
   with "REPAIR TABLE t".
 - When running a "REPAIR TABLE t" or "ALTER TABLE t FORCE" on the above
   table, install a special copy function to trim off the trailing spaces
   which we safely can say that the pre 5.0 mysqld didn't put there. 

mysql-test/r/varbinary.result

@@ -26,3 +26,55 @@ select x,xx from t1;
 x	xx
 1	2
 drop table t1;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` varbinary(255) default NULL,
+  `b` varchar(255) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+select length(a), length(b) from t1;
+length(a)	length(b)
+255	3
+255	3
+CHECK TABLE t1 FOR UPGRADE;
+Table	Op	Msg_type	Msg_text
+test.t1	check	error	Table upgrade required. Please do "REPAIR TABLE `t1`" to fix it!
+REPAIR TABLE t1;
+Table	Op	Msg_type	Msg_text
+test.t1	repair	status	OK
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` varbinary(255) default NULL,
+  `b` varchar(255) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+select length(a), length(b) from t1;
+length(a)	length(b)
+3	3
+3	3
+insert into t1 values("ccc", "ddd");
+select length(a), length(b) from t1;
+length(a)	length(b)
+3	3
+3	3
+3	3
+select hex(a), hex(b) from t1;
+hex(a)	hex(b)
+616161	636363
+626262	646464
+636363	646464
+select concat("'", a, "'"), concat("'", b, "'") from t1;
+concat("'", a, "'")	concat("'", b, "'")
+'aaa'	'ccc'
+'bbb'	'ddd'
+'ccc'	'ddd'
+drop table t1;
+create table t1(a varbinary(255));
+insert into t1 values("aaa   ");
+select length(a) from t1;
+length(a)
+6
+alter table t1 modify a varchar(255);
+select length(a) from t1;
+length(a)
+6

mysql-test/t/varbinary.test

@@ -37,3 +37,43 @@ select x,xx from t1;
 drop table t1;
 
 # End of 4.1 tests
+
+#
+# Bug #19371 VARBINARY() have trailing zeros after upgrade from 4.1
+#
+
+# Test with a saved table from 4.1
+copy_file std_data/bug19371.frm $MYSQLTEST_VARDIR/master-data/test/t1.frm;
+copy_file std_data/bug19371.MYD $MYSQLTEST_VARDIR/master-data/test/t1.MYD;
+copy_file std_data/bug19371.MYI $MYSQLTEST_VARDIR/master-data/test/t1.MYI;
+
+# Everything _looks_ fine
+show create table t1;
+
+# But the length of the varbinary columns are too long
+select length(a), length(b) from t1;
+
+# Run CHECK TABLE, it should indicate table need a REPAIR TABLE
+CHECK TABLE t1 FOR UPGRADE;
+
+# Run REPAIR TABLE to alter the table and repair
+# the varbinary fields
+REPAIR TABLE t1;
+
+# Now check it's back to normal
+show create table t1;
+select length(a), length(b) from t1;
+insert into t1 values("ccc", "ddd");
+select length(a), length(b) from t1;
+select hex(a), hex(b) from t1;
+select concat("'", a, "'"), concat("'", b, "'") from t1;
+
+drop table t1;
+
+# Check that the fix does not affect table created with current version
+create table t1(a varbinary(255));
+insert into t1 values("aaa   ");
+select length(a) from t1;
+alter table t1 modify a varchar(255);
+select length(a) from t1;
+

sql/field_conv.cc

@@ -309,6 +309,21 @@ static void do_field_string(Copy_field *copy)
 }
 
 
+static void do_field_varbinary_pre50(Copy_field *copy)
+{
+  char buff[MAX_FIELD_WIDTH];
+  copy->tmp.set_quick(buff,sizeof(buff),copy->tmp.charset());
+  copy->from_field->val_str(&copy->tmp);
+
+  /* Use the same function as in 4.1 to trim trailing spaces */
+  uint length= my_lengthsp_8bit(&my_charset_bin, copy->tmp.c_ptr_quick(),
+                                copy->from_field->field_length);
+
+  copy->to_field->store(copy->tmp.c_ptr_quick(), length,
+                        copy->tmp.charset());
+}
+
+
 static void do_field_int(Copy_field *copy)
 {
   longlong value= copy->from_field->val_int();
@@ -570,6 +585,15 @@ void (*Copy_field::get_copy_func(Field *to,Field *from))(Copy_field*)
     // Check if identical fields
     if (from->result_type() == STRING_RESULT)
     {
+      /*
+        Detect copy from pre 5.0 varbinary to varbinary as of 5.0 and
+        use special copy function that removes trailing spaces and thus
+        repairs data.
+      */
+      if (from->type() == MYSQL_TYPE_VAR_STRING && !from->has_charset() &&
+          to->type() == MYSQL_TYPE_VARCHAR && !to->has_charset())
+        return do_field_varbinary_pre50;
+
       /*
         If we are copying date or datetime's we have to check the dates
         if we don't allow 'all' dates.

sql/handler.cc

@@ -1972,6 +1972,10 @@ int handler::check_old_types()
       {
         return HA_ADMIN_NEEDS_ALTER;
       }
+      if ((*field)->type() == MYSQL_TYPE_VAR_STRING)
+      {
+        return HA_ADMIN_NEEDS_ALTER;
+      }
     }
   }
   return 0;