Horton

Re: Online enabling of checksums

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Daniel Gustafsson <daniel@yesql.se>
Cc: Magnus Hagander <magnus@hagander.net>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Andrey Borodin <x4mmm@yandex-team.ru>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Michael Banck <michael.banck@credativ.de>, Robert Haas <robertmhaas@gmail.com>, Greg Stark <stark@mit.edu>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-04-06T21:33:48Z
Lists: pgsql-hackers 
On 2018-04-06 02:28:17 +0200, Daniel Gustafsson wrote:
> Looking into the isolationtester failure on piculet, which builds using
> --disable-atomics, and locust which doesn’t have atomics, the code for
> pg_atomic_test_set_flag seems a bit odd.
> 
> TAS() is defined to return zero if successful, and pg_atomic_test_set_flag()
> defined to return True if it could set.  When running without atomics, don’t we
> need to do something like the below diff to make these APIs match?  :
> 
> --- a/src/backend/port/atomics.c
> +++ b/src/backend/port/atomics.c
> @@ -73,7 +73,7 @@ pg_atomic_init_flag_impl(volatile pg_atomic_flag *ptr)
>  bool
>  pg_atomic_test_set_flag_impl(volatile pg_atomic_flag *ptr)
>  {
> -       return TAS((slock_t *) &ptr->sema);
> +       return TAS((slock_t *) &ptr->sema) == 0;
>  }

Yes, this looks wrong.

Greetings,

Andres Freund

Commits

  1. Online enabling and disabling of data checksums

  2. Deactive flapping checksum isolation tests.

  3. Add support for coordinating record typmods among parallel workers.