Re: [PATCHES] Trivial patch to double vacuum speed on tables with no indexes

Gregory Stark wrote:
>
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
>
> > Tom Lane wrote:
> >> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> >> > Patch applied. Thanks.
> >>
> >> Wait a minute. This patch changes the behavior so that
> >> LockBufferForCleanup is applied to *every* heap page, not only the ones
> >> where there are removable tuples. It's not hard to imagine scenarios
> >> where that results in severe system-wide performance degradation.
> >> Has there been any real-world testing of this idea?
> >
> > I see the no-index case now:
> >
> > + if (nindexes)
> > + LockBuffer(buf, BUFFER_LOCK_SHARE);
> > + else
> > + LockBufferForCleanup(buf);
> >
> > Let's see what Greg says, or revert.
>
> Hm, that's a good point. I could return it to the original method where it
> released the share lock and did he LockBufferForCleanup only if necessary. I
> thought it was awkward to acquire a lock then release it to acquire a
> different lock on the same buffer but it's true that it doesn't always have to
> acquire the second lock.

This rush to apply patches just because no one seems to be capable of
keeping up with them not being reviewed, is starting to get a bit
worrisome.

--
Alvaro Herrera http://www.CommandPrompt.com/
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