Re: Parallel tuplesort (for parallel B-Tree index creation)

On 2017-02-10 07:52:57 -0500, Robert Haas wrote:
> On Thu, Feb 9, 2017 at 6:38 PM, Thomas Munro
> > Up until two minutes ago I assumed that policy would leave only two
> > possibilities: you attach to the DSM segment and attach to the
> > SharedBufFileManager successfully or you attach to the DSM segment and
> > then die horribly (but not throw) and the postmaster restarts the
> > whole cluster and blows all temp files away with RemovePgTempFiles().
> > But I see now in the comment of that function that crash-induced
> > restarts don't call that because "someone might want to examine the
> > temp files for debugging purposes". Given that policy for regular
> > private BufFiles, I don't see why that shouldn't apply equally to
> > shared files: after a crash restart, you may have some junk files that
> > won't be cleaned up until your next clean restart, whether they were
> > private or shared BufFiles.
>
> I think most people (other than Tom) would agree that that policy
> isn't really sensible any more; it probably made sense when the
> PostgreSQL user community was much smaller and consisted mostly of the
> people developing PostgreSQL, but these days it's much more likely to
> cause operational headaches than to help a developer debug.

FWIW, we have restart_after_crash = false. If you need to debug things,
you can enable that. Hence the whole RemovePgTempFiles() crash-restart
exemption isn't required anymore, we have a much more targeted solution.

- Andres