From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
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 16:54:38 |
Message-ID: | 20160502165438.yu6inlsyv4babyie@alap3.anarazel.de |
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Lists: | pgsql-bugs pgsql-hackers |
On 2016-05-02 12:44:53 -0400, Robert Haas wrote:
> 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?
Sure, attached.
I'm not sure this is the best way to go about this. I can see valid
arguments for *always* using _mdfd_openseg() in mdsync(); and I'm
wondering whether we shouldn't make EXTENSION_* into a bitmask
(extend,extend_recovery,return_null,open_deleted).
Andres
Attachment | Content-Type | Size |
---|---|---|
wip_mdsync.patch | text/x-patch | 1.5 KB |
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