Re: Write Ahead Logging for Hash Indexes

On Mon, Sep 12, 2016 at 11:29 AM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
>
>
> My test program (as posted) injects crashes and then checks the
> post-crash-recovery system for consistency, so it cannot be run as-is
> without the WAL patch. I also ran the test with crashing turned off (just
> change the JJ* variables at the stop of the do.sh to all be set to the empty
> string), and in that case I didn't see either problem, but it it could just
> be that I that I didn't run it long enough.
>
> It should have been long enough to detect the rather common "buffer <x> is
> not owned by resource owner Portal" problem, so that one I think is specific
> to the WAL patch (probably the part which tries to complete bucket splits
> when it detects one was started but not completed?)
>

Both the problem seems to be due to same reason and in concurrent hash
index patch. So what is happening here is that we are trying to unpin
the old bucket buffer twice. We need to scan the old bucket when
there is a incomplete-split, so the issue here is that during split
the system has crashed and after restart, during old bucket scan it
tries to unpin the old primary bucket buffer twice when the new bucket
has additional overflow pages. I will post the updated patch on
concurrent hash index thread. Once, I post the patch, it is better if
you try to reproduce the issue once more.

Thanks to Ashutosh Sharma who has offlist shared the call stack after
reproducing the problem.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com