| From: | Claudio Freire <klaussfreire(at)gmail(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Cc: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Andres Freund <andres(at)anarazel(dot)de>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Anastasia Lubennikova <a(dot)lubennikova(at)postgrespro(dot)ru>, Anastasia Lubennikova <lubennikovaav(at)gmail(dot)com>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Vacuum: allow usage of more than 1GB of work mem |
| Date: | 2018-02-08 03:13:09 |
| Message-ID: | CAGTBQpZUbCxBu=Ckow3ydFFPqrRFQ5NxGUQExgK7d=9N24bmYg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Feb 7, 2018 at 11:29 PM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> Claudio Freire wrote:
>> On Wed, Feb 7, 2018 at 8:52 PM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
>> >> Waiting as you say would be akin to what the patch does by putting
>> >> vacuum on its own parallel group.
>> >
>> > I don't think it's the same. We don't need to wait until all the
>> > concurrent tests are done -- we only need to wait until the transactions
>> > that were current when the delete finished are done, which is very
>> > different since each test runs tons of small transactions rather than
>> > one single big transaction.
>>
>> Um... maybe "lock pg_class" ?
>
> I was thinking in first doing
> SELECT array_agg(DISTINCT virtualtransaction) vxids
> FROM pg_locks \gset
>
> and then in a DO block loop until
>
> SELECT DISTINCT virtualtransaction
> FROM pg_locks
> INTERSECT
> SELECT (unnest(:'vxids'::text[]));
>
> returns empty; something along those lines.
Isn't it the same though?
I can't think how a transaction wouldn't be holding at least an access
share on pg_class.
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