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From "Charlie Hubbard" <charlie.hubb...@gmail.com>
Subject Reducing memory usage
Date Sun, 07 Oct 2007 14:21:15 GMT

I have a database that I have been storing binary data in a Blob
column.  I've decided that it was a bad idea and I'd like to remove it
from the DB and store it on the filesystem.  I've written a small
program to extract the contents from the DB and save it to the file
system.  It works except it runs out of memory using the default 64
MB.  While I could increase the -Xmx setting it seems superflous.
I've profiled the application and majority of the memory is being
occupied by derby.  I see lots of classes like
org.apache.derby.impl.services.cache.CachedItem and
org.apache.derby.impl.store.raw.data.StoredPage holding 32KB byte

Is there a way to change derby so that it would drop those cached
buffers?  Or a way to turn off caching for blobs?  Or is there a way
to optimize the memory a little more so that it would run in a smaller

This program will have to run on DB that could be in the GB size.  I
just need to extract the contents and save it out to disk.  Modify the
DB to drop the Blobs, and re-attach those records to the filesystem
paths of the files.


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