This document compares the Java embedded databases HSQLDB and H2 for use in continuous integration. It finds that H2 is better suited because it is more compatible with MySQL, has easier installation than HSQLDB, and allows for easier migration from HSQLDB. Initial tests of DDL statements show H2 is almost compliant with MySQL, with a few exceptions. H2 is also faster than HSQLDB and allows dropping all objects at once. The document recommends starting to use H2 going forward.

1. Java memory DB
HSQDB versus H2
By Franck Benault
Created 12/09/2014
Last updated 21/09/2014

2. HSQDB versus H2 plan

3. HSQDB versus H2 plan
● Issue in continous integration
● Memory DB
● H2
● Good results

4. Issue in continous integration
● Production
– MySQL or Oracle
● Jenkins nothing -> memory DB
● Result specific code HSQLDB / MySQL
– Limit
– Update with two tables involved
– Delete with two tables involved
– SQL script for MySQL not compliant for HSQLDB

5. Java memory database
● Java memory database
– Embedded mode
– Jar in maven repository
– Hibernate Dialect
● HSQLDB
● H2
● Apache Derby
– Issue with logging not fixed

6. Java memory database
● URL = jdbc:h2:mem:test_mem

7. Java memory database
● URL = jdbc:h2:tcp://localhost/mem:test

8. Java memory installation
● H2 and HSQLDB
– Just a zip to extract, server and client

9. Good results with H2
● Better = closer to MySQL
● Limit MySQL H2
– delete from contracts limit 100;
● HSQLDB (and H2)
– Delete from contract where rownum()<=100 ;

10. Good results with H2
● MySQL and H2
– Show tables;
● HSQLDB
– SELECT * FROM
INFORMATION_SCHEMA.SYSTEM_TABLES where
TABLE_TYPE='TABLE'

11. Good results with H2
● Better = closer to MySQL
● MySQL and H2
– Explain available
● HSQLDB
– I don't know ...

12. Good results with H2
● First tests, ddl are H2 almost compliant
– create table contracts(
– id_contract varchar(50) NOT NULL,
– contract_status varchar(50) NOT NULL,
– id_acquirer varchar(50) DEFAULT NULL,
– //not primary key pk_contract(id_contract)
– CONSTRAINT pk_contract PRIMARY KEY (id_contract)
– );
● H2 constraint name must be unique in the schema (MySQL, unique in the table)
● H2 zerofill not supported
● H2 comment starting with by « # » not supported

13. Good results with H2 (in the future)
● MySQL compatibility: update test1 t1, test2 t2 set t1.id =
t2.id where t1.id = t2.id;
– H2
● http://www.h2database.com/html/roadmap.html
– Priority2
– HSQLDB
● Not planned
● Same issue for Delete

14. Good results with H2
● Migration very easy
● Positive feedback
● Additional points
– H2 is a little faster than HSQLDB
– H2 « drop all objects »

15. HSQLDB / H2 conclusion
● When will you start with H2 ?