HSQLDB - How is the "VARCHAR" type storage handled?

Question

My question must be quiet stupid for some of you, but I've been unable to find the answer directly on HSQLDB website, google, or here (I may I've missed something, but I dont think so, as there isn't much on the web regarding HSQLDB compared to other well known databases).

To explain in more details, my background is a more Oracle DB background... I'm starting with HSQLDB and I wondered, as we can't use type declaration such as:

• "mycolumn VARCHAR(25 CHAR)"
• "mycolumn VARCHAR(25 BYTE)"

How was the storage managed on HSQLDB as I have to use "mycolumn VARCHAR(25)" instead of the previous solutions. I would be glad if anyone got a good description or a link regarding how characters are stored, to avoid storage issues with special chars for example.

Thanks in advance !

Antoine

Answer 1

HSQLDB uses the Unicode character set with UTF-16 encoding. Therefore all possible characters can be stored in a CHAR, VARCHAR or CLOB column. The declaration size of a VARCHAR column refers to the maximum number of UTF-16 characters allowed.

The physical storage of VARCHAR data on disk is similar to UTF-8 and takes one byte per each Latin character but more than one for other characters. The user does not see this encoding and its only significance is the amount of disk space used for long VARCHAR data.