Horton

Re: SimpleLruTruncate() mutual exclusion

Noah Misch <noah@leadboat.com>

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From: Noah Misch <noah@leadboat.com>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgresql.org
Date: 2020-01-31T08:42:13Z
Lists: pgsql-hackers 
On Thu, Jan 30, 2020 at 04:34:33PM +0100, Dmitry Dolgov wrote:
> > On Sun, Nov 17, 2019 at 10:14:26PM -0800, Noah Misch wrote:
> > > I'm probably missing something, so just wanted to clarify. Do I
> > > understand correctly, that thread [1] and this one are independent, and
> > > it is assumed in the scenario above that we're at the end of XID space,
> > > but not necessarily having rounding issues? I'm a bit confused, since
> > > the reproduce script does something about cutoffPage, and I'm not sure
> > > if it's important or not.
> >
> > I think the repro recipe contained an early fix for the other thread's bug.
> > While they're independent in principle, I likely never reproduced this bug
> > without having a fix in place for the other thread's bug.  The bug in the
> > other thread was easier to hit.
> 
> Just to clarify, since the CF item for this patch was withdrawn
> recently. Does it mean that eventually the thread [1] covers this one
> too?
> 
> [1]: https://www.postgresql.org/message-id/flat/20190202083822.GC32531%40gust.leadboat.com

I withdrew $SUBJECT because, if someone reviews one of my patches, I want it
to be the one you cite in [1].  I plan not to commit [1] without a Ready for
Committer, and I plan not to commit $SUBJECT before committing [1].  I would
be willing to commit $SUBJECT without getting a review, however.

Commits

  1. Prevent concurrent SimpleLruTruncate() for any given SLRU.

  2. Rename SLRU structures and associated LWLocks.

  3. Improve ANALYZE's handling of concurrent-update scenarios.

  4. Avoid consuming an XID during vac_truncate_clog().