[TAJO-911] Refactoring MySQL/MariaDB Catalog Store

[charsyam]

MySQLStore and MariaDBStore are almost same.
so it is better to extract parent class for them.

[hyunsik]

The patch looks good to me. It's just a question. Did you test it on a local or real cluster? This is because I'm concerned with the difficulty of integrated unit tests of catalog drivers like MySQL or MariaDB.

[charsyam]

@hyunsik I just test it in my local system.
I just changed TestCatalog.java to use MariaDB Driver.
ant it made Tables well.

after test. TestCatalog made below tables;

MariaDB [tajo]> show tables;
+-------------------+
| Tables_in_tajo |
+-------------------+
| COLUMNS |
| DATABASES_ |
| INDEXES |
| META |
| OPTIONS |
| PARTITIONS |
| PARTITION_METHODS |
| STATS |
| TABLES |
| TABLESPACES |
+-------------------+

MariaDB [tajo]> select * from DATABASES_;
+-------+---------+----------+
| DB_ID | DB_NAME | SPACE_ID |
+-------+---------+----------+
| 1 | default | 1 |
| 20 | tmpdb3 | 1 |
| 21 | tmpdb4 | 1 |
+-------+---------+----------+

[hyunsik]

+1
the patch looks good to me. Thank you for sharing your test result. I've also tested TestCatalog agsinst MySQL. I'll commit it shortly.

This documentation may be useful to you.
https://cwiki.apache.org/confluence/display/TAJO/Unit+Tests

Aside from this issue, I'm concerning with integration test of mysql/mariadb catalog driver. For example, we can do 'mvn clean install' with an external mysql as a catalog store. I'll discuss it more in another Jira issue when we needed.
Aside from this issue, I'm concerning with