On Mon, Feb 02, 2009 at 09:48:37AM -0800, Scara Maccai wrote: > > I need to store a lot of int8 columns (2000-2500) in a table. > > I was thinking about using int8[] An array of ints sounds like the way to go here as you wouldn't be able to have that many columns. TOAST is one non-obvious implementation artifact that may cause extra work to be done and may cause confusion. Tuples in PG can be a maximum of 8KB and hence 2000 INT8 values would only just fit and 2500 values wouldn't. TOAST docs are available here: http://www.postgresql.org/docs/current/static/storage-toast.html > , and I would like to know: > > 1) is there a max size for arrays? I guess I could have 1 GB "worth" > > of values, Not that I'm aware of; as a quick test: CREATE TABLE arrtest ( v INT8[] ); INSERT INTO arrtest SELECT ARRAY(SELECT generate_series(1,10000000)); worked (very slowly) for me, but 100000000 failed with an out of memory error (32bit build). > > but I would like a confirmation > > 2) there won't be any updates, only inserts and selects; since I > > will be using ZFS would there be any benefit in changing the block > > size (for example to 32K) in postgresql? No idea, maybe someone else? > > Would it be better to use > > ZFS compression instead of postgresql's (TOAST)? That is: should I > > EXTERNAL for that array column and set compression=on for ZFS? I > > tried ZFS compression=on a 200 columns table and it worked faster > > than with compression=off.... Oh, I guess you know about TOAST. Otherwise I can't help much, sorry! -- Sam http://samason.me.uk/ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
