> Unqualified SELECT COUNT(*) FROM foo is one of the most expensive operations
> you can do on your system, since the visibility information has to be
> checked
> on disk for each row. Instead, try real queries on real data, and post here
> if some are too slow for you.
Ok, that's a bad example. I'm learning :-) Is insert ... select also
really expensive then? I have a table loaded with message-id and path
information of currently-existing messages. It has ~20 million rows.
Trying to do "INSERT INTO Messages(path, msgid) SELECT (path, msgid)
FROM tmpMessages" took a really long time before psql died with an
out-of-memory error. Is there a more sane way to do a table copy, or
should I have just dropped all the indices from the Message table and
loaded into that?
Thanks!