Horton

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

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: "Wood, Dan" <hexpert@amazon.com>
Cc: Michael Paquier <michael.paquier@gmail.com>, "Wong, Yi Wen" <yiwong@amazon.com>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2017-10-06T13:18:30Z
Lists: pgsql-hackers

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Wood, Dan wrote:
> Yes, I’ve been testing 9.6.  I’ll try Alvaro’s patch today.
> 
> I would prefer to focus on either latest 9X or 11dev.  

I tested my patch on 9.4 and 9.5 today and it seems to close the problem
(with the patch, I waited 10x as many iterations as it took for the
problem to occur ~10 times without the patch), but I can reproduce a
problem in 9.6 with my patch installed.  There must be something new in
9.6 that is causing the problem to reappear.

> Does Alvaro’s patch presume any of the other patch to set COMMITTED in
> the freeze code?

I don't know what you mean.  Here is the 9.6 version of my patch.  Note
that HEAP_XMIN_FROZEN (which uses the XMIN_COMMITTED bit as I recall)
was introduced in 9.4.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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.