On Wed, 20 Aug 2003, Brian McCane wrote:4) Can I disable the compression to improve storage speed if the compression algorithm is not as good as deflate
See ALTER TABLE ALTER COLUMN SET STORAGE (I would guess you would want external, but I'm not 100% sure, check the docs :) )
Yes, EXTERNAL is correct. We had a good thread on this topic on PERFORM a couple of weeks ago.
Starts here: http://archives.postgresql.org/pgsql-performance/2003-08/msg00030.php Ends here: http://archives.postgresql.org/pgsql-performance/2003-08/msg00144.php
Note the issue with UPDATE in place of the data. You need to concatenate an empty string to force the change of storage.
Also, I'm not sure if storing a compressed version in a text field is a good idea. I'd think that bytea would be a better match.
You can pretty much guarantee problems if you store binary (i.e. pre-compressed) data in a text field. If your uncompressed data is not binary, you should probably do one of these options:
1) pre-compress and store in a bytea field with storage set to EXTERNAL
2) store as-is in a text field and let Postgres do the compression for
you
3) store as-is in a text field with storage set to EXTERNAL
Personally, I'd use #3 if you consider disk space cheap and performance important, or #2 if you really need the data compressed. You might get moderately better compression using an external program, but it is probably at a big performance hit.
HTH,
Joe
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