Re: [BUGS] Breakage with VACUUM ANALYSE + partitions

On 2016-05-02 12:29:45 -0400, Robert Haas wrote:
> On Fri, Apr 29, 2016 at 7:58 PM, Andres Freund <andres@anarazel.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?

FWIW, falling back to _mdfd_openseg() fixes the issue.

Andres