Horton

Re: [HACKERS] pgsql: Fix freezing of a dead HOT-updated tuple

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-committers <pgsql-committers@postgresql.org>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Stephen Frost <sfrost@snowman.net>, Andres Freund <andres@anarazel.de>, "Wood, Dan" <hexpert@amazon.com>, Peter Geoghegan <pg@bowt.ie>, "Wong, Yi Wen" <yiwong@amazon.com>, Michael Paquier <michael.paquier@gmail.com>
Date: 2017-11-02T17:08:10Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> Just to be clear, it looks like "Fix freezing of a dead HOT-updated
> tuple" (46c35116ae1acc8826705ef2a7b5d9110f9d6e84) went in before 10.0
> was stamped, but "Fix traversal of half-frozen update chains"
> (22576734b805fb0952f9be841ca8f643694ee868) went in afterwards and is
> therefore unreleased at present.

Thanks for doing this analysis of the actual effects in 10.0.

> Personally, I think it would be best to push the release out a week.

I would only be in favor of that if there were some reason to think that
the bug is worse now than it's been in the four years since 9.3 was
released.  Otherwise, we should ship the bug fixes we have on-schedule.
I think it's a very very safe bet that there are other data-loss-causing
bugs in there, so I see no good reason for panicking over this one.

> ... and (I know you're all tired of hearing me say this) patches that
> implicate the on-disk format are scary.

Agreed, but how is that relevant now that the bogus patches are reverted?

			regards, tom lane

Commits

  1. Backport addition of rs_old_rel to rewriteheap's state.

  2. Perform a lot more sanity checks when freezing tuples.

  3. Revert bogus fixes of HOT-freezing bug

  4. Fix traversal of half-frozen update chains

  5. Fix freezing of a dead HOT-updated tuple

  6. During index build, check and elog (not just Assert) for broken HOT chain.

  7. Fix WAL replay of locking an updated tuple

  8. Change the way we mark tuples as frozen.