On Fri, 2008-05-30 at 14:22 +0530, Pavan Deolasee wrote: > For large tables, two heap scans along with several additional page > writes doesn't seem to the cost we can afford, especially in IO-bound > application. IMHO a timed wait is not such a bad thing. Note that its > all about VACUUM which is a background, maintenance activity and it > won't harm to delay it by few seconds or even minutes. Also, as I said > earlier "waiting" is a minor detail, may be there is a better way to > do things. > > Unless there are some strong objections, I would like to give it a > shot and see if there are any real benefits. We can then fix any > regression cases. Let me know if somebody thinks there are certain > show stoppers or the benefits of avoiding a second scan on a large > table is not worth. I personally have a strong feeling that it's worth > the efforts.
I'm not really clear what you intend to do now. We both agreed that avoiding a second pass is a good thing. What I still don't accept is that an unconstrained wait is justifiable. You've just said its a minor detail, but that's not the way I see it. It might be a second, but it might be an hour or more. If I run a VACUUM at 0700, thinking it will finish by 0900 before my database gets busy, it is a very bad thing to find that it only started at 0900 and is now interfering with my business workload. A non-waiting solution seems like the only way to proceed. Is this a non-issue anyway, with DSM? -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
