* Joe Maldonado (jmaldonado@xxxxxxxxxxxxxxx) wrote: > It seems that TRUNCATE is first posting a lock on the table and then > waiting for other transactions to finish before truncating the table > thus blocking all other operations. > > Is this what is actually going on or am I missing something else? and is > there a way to prevent this condition from happening? TRUNCATE isn't MVCC-safe, for one thing. For another, yes, it uses a much heavier lock on the table. If you don't want to use a heavy lock on the table then you'll need to delete from *;. I've got a similar setup to you and was looking at using truncate for it but I've been starting to think just interjecting a vacuum in the middle might be better. ie: Instead of using: truncate x; insert into x; Doing: delete from x; vacuum x; insert into x; I'm not really sure which would be faster, so I'm kind of curious about that. In my case people are rarely using the table at the same time they'd be truncating/delete'ing it (the UI doesn't actually allow it) so the total time may be close between the two. For your case that might not be true since the vacuum might not be able to do much due to the other select's, which means the table ends up being double the size due to the old tuples, etc. If someone else has a better solution I'd love to hear it. Thanks, Stephen
Attachment:
signature.asc
Description: Digital signature
