"Simon Riggs" <[EMAIL PROTECTED]> writes: > On Wed, 2007-02-28 at 13:53 +0900, Galy Lee wrote: >> In the current implementation of concurrent vacuum, the third is not >> satisfied obviously, the first issue comes to my mind is the >> lazy_truncate_heap, it takes AccessExclusiveLock for a long time, >> that is problematic.
> Are you saying you know for certain this lock is held for a long time, > or are you just saying you think it is? If you have some evidence for > long truncation times then that would be a separate issue of concern, > since that might starve out normal users. Please say more? lazy_truncate_heap does a ConditionalLockAcquire, that is, it won't succeed in acquiring the exclusive lock if there is any competition. And I find it hard to believe that it will hold the lock very long if it does get it --- in most scenarios it won't be possible to remove very many pages, so the scan won't take long. (Of course that is arguably a bug, but until you can fix things so that an average VACUUM *can* remove a lot of pages, it's hardly profitable to worry about whether this step creates a concurrency problem.) So I agree with Simon: if you want us to believe there's a performance issue here, please present some evidence. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly