hooks for supporting third party blobs?

A recent project of ours involved storing/fetching some reasonably large
datasets in a home-brew datatype. The datasets tended to range from a few
megabytes, to several gigabytes. We were seeing some nonlinear slowness
with using native large objects with larger datasets, presumably due to the
increasing depth of the btree index used to track all the little pieces of
the blobs.

After some careful consideration, we implemented an alternative to large
objects, a system based on storing files in a particular directory, and
storing a reference to the files in the database. It worked and gave us
good and consistent performance. However, it doesn't support transactions
(no isolation, no rollback). We can probably implement some backend code to
support such functionality, but the trick is getting the postgres server to
keep our code in the loop (so to speak) about when a rollback should be
done (and to when).

Is anyone aware of any hooks to support schemes such as ours, or has solved
a similar problem?

Thank you.

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Eric Davies, M.Sc.
Barrodale Computing Services Ltd.
Tel: (250) 472-4372 Fax: (250) 472-4373
Web: http://www.barrodale.com
Email: eric(at)barrodale(dot)com
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