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Posted to derby-dev@db.apache.org by manju sherif <ma...@yahoo.com> on 2005/08/10 20:23:31 UTC
Is Derby and in memory database?
Hi,
Is derby an in memory database ? We are looking at in memoery databases for high reponse reads and inserts. How does Derby compare with HSQL as an in memory database?
Thanks
Manju
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Re: Is Derby and in memory database?
Posted by "Jean T. Anderson" <jt...@bristowhill.com>.
manju sherif wrote:
> Hi,
>
> Is derby an in memory database ? We are looking at in memoery databases
> for high reponse reads and inserts. How does Derby compare with HSQL as
> an in memory database?
In-memory database support is on the Apache Derby To Do list at
http://db.apache.org/derby/DerbyToDo.html ; however, I don't believe it
is actively being worked on. The developers on this list can say for sure.
Dan Debrunner listed 2 key differences between hsql and derby in this
post to derby-user@db.apache.org:
http://mail-archives.apache.org/mod_mbox/db-derby-user/200409.mbox/%3c41409451.6060506@debrunners.com%3e
An extract from his post is down below:
> These are two main differences I see from a quick look at the HSQL docs.
>
> Memory Use
>
> Derby is setup like a traditional database system where data is stored
> on disk and a subset of that data is cached in a buffer cache or pool.
>
> HSQL by default uses MEMORY tables (for standard CREATE TABLE
> statements), this always stores the entire data in memory. Thus this is
> fast, but obviously consumes memory. It is useful to look a process
> sizes as well as absolute times when running benchmarks.
> http://hsqldb.sourceforge.net/doc/guide/ch01.html#N1021D
>
>
> Transaction Model
>
> Derby provides a complete thread-safe multi-connection model supporting
> all four JDBC/SQL isolation levels. Row level locking is used to support
> these isolation models.
>
> HSQL provides the single isolation level, READ_UNCOMMITTED, also known
> as dirty read, even for update transactions. Issues with this model are
> described in the HSQL documentation at:
> http://hsqldb.sourceforge.net/doc/guide/ch02.html#N104D5
I hope this helps.
regards,
-jean