| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Thom Brown <thom(at)linux(dot)com>, Abhijit Menon-Sen <ams(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [BUGS] Breakage with VACUUM ANALYSE + partitions |
| Date: | 2016-05-02 16:44:53 |
| Message-ID: | CA+Tgmoajiv-4840wHpx0o-LJ7mqSGrnCtRH8MOoJkL2A-GF2Ww@mail.gmail.com |
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| Lists: | pgsql-bugs pgsql-hackers |
On Mon, May 2, 2016 at 12:41 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2016-05-02 12:29:45 -0400, Robert Haas wrote:
>> On Fri, Apr 29, 2016 at 7:58 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> > Basically the reason for the problem is that mdsync() needs to access
>> > "formally non-existant segments" (as in ones where previous segments are
>> > < RELSEG_SIZE), because we queue (and the might be preexistant) fsync
>> > requests via register_dirty_segment() in mdtruncate().
>>
>> Shouldn't we just throw those flush requests away?
>
> Well, we explicity make them for truncations (register_dirty_segment()
> calls in mdtruncate()). There's no comment as to why - I suspect the
> idea is that you want to make sure the truncation sticks in case of
> crash?
I dunno, I don't understand this well enough yet.
> FWIW, falling back to _mdfd_openseg() fixes the issue.
Can you post a patch?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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