MDEV-13636 ALTER TABLE ... DELAY_KEY_WRITE=1 creates table copy for MyISAM...

MDEV-13636 ALTER TABLE ... DELAY_KEY_WRITE=1 creates table copy for MyISAM table with DATA DIRECTORY/INDEX DIRECTORY options

correct detection of changes in DATA/INDEX DIRECTORY

mysql-test/r/symlink.result

@@ -227,3 +227,15 @@ DROP DATABASE x;
 CREATE TABLE test.t1(id INT(11)) ENGINE MYISAM
 DATA DIRECTORY "MYSQLTEST_VARDIR/tmp";
 DROP TABLE test.t1;
+use test;
+create table t1(c1 int, c2 int, c3 varchar(100)) engine=MyISAM data directory='MYSQL_TMP_DIR' index directory = 'MYSQL_TMP_DIR';
+insert t1 values (1,2,3), (2,3,4), (3,4,5), (4,5,6), (5,6,7), (6,7,8), (7,8,9);
+alter online table t1 delay_key_write=1;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c1` int(11) DEFAULT NULL,
+  `c2` int(11) DEFAULT NULL,
+  `c3` varchar(100) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 DELAY_KEY_WRITE=1 DATA DIRECTORY='MYSQL_TMP_DIR/' INDEX DIRECTORY='MYSQL_TMP_DIR/'
+drop table t1;

mysql-test/t/symlink.test

@@ -316,3 +316,28 @@ eval CREATE TABLE test.t1(id INT(11)) ENGINE MYISAM
 DATA DIRECTORY "$MYSQLTEST_VARDIR/tmp";
 
 DROP TABLE test.t1;
+use test;
+
+#
+# End of 5.5 tests
+#
+
+#
+# End of 10.0 tests
+#
+
+#
+# MDEV-13636 ALTER TABLE ... DELAY_KEY_WRITE=1 creates table copy for MyISAM table with DATA DIRECTORY/INDEX DIRECTORY options
+#
+replace_result $MYSQL_TMP_DIR MYSQL_TMP_DIR;
+eval
+create table t1(c1 int, c2 int, c3 varchar(100)) engine=MyISAM data directory='$MYSQL_TMP_DIR' index directory = '$MYSQL_TMP_DIR';
+insert t1 values (1,2,3), (2,3,4), (3,4,5), (4,5,6), (5,6,7), (6,7,8), (7,8,9);
+alter online table t1 delay_key_write=1;
+replace_result $MYSQL_TMP_DIR MYSQL_TMP_DIR;
+show create table t1;
+drop table t1;
+
+#
+# End of 10.1 tests
+#

storage/myisam/ha_myisam.cc

@@ -2261,6 +2261,17 @@ ha_myisam::check_if_supported_inplace_alter(TABLE *new_table,
 }
 
 
+static bool directories_differ(const char *d1, const char *d2)
+{
+  if (!d1 && !d2)
+    return false;
+  if (!d1 || !d2)
+    return true;
+  size_t l1= dirname_length(d1), l2= dirname_length(d2);
+  return l1 != l2 || strncmp(d1, d2, l1);
+}
+
+
 bool ha_myisam::check_if_incompatible_data(HA_CREATE_INFO *create_info,
 					   uint table_changes)
 {
@@ -2268,8 +2279,8 @@ bool ha_myisam::check_if_incompatible_data(HA_CREATE_INFO *create_info,
 
   if ((create_info->used_fields & HA_CREATE_USED_AUTO &&
        create_info->auto_increment_value != stats.auto_increment_value) ||
-      create_info->data_file_name != data_file_name ||
-      create_info->index_file_name != index_file_name ||
+      directories_differ(create_info->data_file_name, data_file_name) ||
+      directories_differ(create_info->index_file_name, index_file_name) ||
       table_changes == IS_EQUAL_NO ||
       table_changes & IS_EQUAL_PACK_LENGTH) // Not implemented yet
     return COMPATIBLE_DATA_NO;