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From "Phil Bradley" <ph...@tower.ie>
Subject Re: Derby eating up disk space + how to trigger ReclaimSpace elegantly
Date Mon, 08 Aug 2011 10:45:29 GMT

Hi,

For what it's worth, I had an approximately similar experience
with approximately similar volumes of data on a desktop app using
Derby embedded. I introduced a daily compress of all tables using
the following command (for each table):

call SYSCS_UTIL.SYSCS_COMPRESS_TABLE('MYSCHEMA', 'MYTABLE', 0)

The schedule for this was handled at the application level rather
than the derby level. Specifically, we used quartz to do the
scheduling.

Also, as you mention, this is on a per table basis. I don't
believe there is a single command that you can use to compress
the whole database so we just use the database metadata to list
all tables and apply the procedure to each.

Regards,
Phil





On Fri, 05 Aug 2011 16:35 +0200, "De Meyer Tim"
<Tim.DeMeyer@cegeka.be> wrote:

  Hi,
  We're working on a java webapp and using a derby database
  (v10.5) in embedded mode.
  The first version of the application went live about 2 months
  ago.
  The application is used to make invoices and we also store the
  XML of an invoice document (input data for generating a PDF
  against a template).
  Today, the database is about 1,7GB on disk.
  During these 2 months, we've released some minor upgrades,
  including database migration scripts (like extra tables for
  new functionality).
  Now we've noticed that, when we ran our latest upgrade, the
  database has suddenly shrunk to a size of 600MB.
  This latest upgrade contained a migration script that dropped
  a no longer needed column on practically every table.
  It's after executing this script that the shrink happened.
  We did some debugging and hit suspend when the disk size
  started shrinking, it lead us to a Derby class called
  "ReclaimSpace".
  The shrink was a bliss, because the customer was already
  complaining about the large size on disk :-)
  We're afraid the database will start using up unnecessary
  space again soon, and of course, we're not going to have a
  similar migration script in every upgrade.
  Is there an elegant way to configure derby to do this cleaning
  continuously, or to let our webapp instruct derby to do some
  cleaning?
  We're launching the webapp from within a small java webstart
  app (we launch a Jetty and attach our war file), so it's even
  OK for us to write some java code to do it programmatically.
  We've found this, but it's on a per table basis.
  [1]http://db.apache.org/derby/docs/10.1/adminguide/cadminspace
  21579.html
  [2]http://db.apache.org/derby/docs/10.5/ref/rrefaltertablecomp
  ress.html
  By the way, we're running about 10 of these webapps on
  different desktop PC's.
  Each webapp synchronizes its data to a server running a
  postgresql 9 database.
  This means that this postgres database accumulates all the
  data of these 10 webapps (some data is shared, so it's not
  times ten).
  The size of this postgres DB is less than 1GB, which we think
  is surprisingly small compared to the derby DB for one webapp.
  Any help on all of this would be more than welcome.
  Kind regards,
  Tim De Meyer

References

1. http://db.apache.org/derby/docs/10.1/adminguide/cadminspace21579.html
2. http://db.apache.org/derby/docs/10.5/ref/rrefaltertablecompress.html

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