Horton

Re: Hash Indexes

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Jesper Pedersen <jesper.pedersen@redhat.com>, Mithun Cy <mithun.cy@enterprisedb.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2016-12-06T12:00:27Z
Lists: pgsql-hackers 
On Tue, Dec 6, 2016 at 1:29 PM, Jeff Janes <jeff.janes@gmail.com> wrote:
>
>
> I just occasionally insert a bunch of equal tuples, which have to be in
> overflow pages no matter how much splitting happens.
>
> I am getting vacuum errors against HEAD, after about 20 minutes or so (8
> cores).
>
> 49233  XX002 2016-12-05 23:06:44.087 PST:ERROR:  index "foo_index_idx"
> contains unexpected zero page at block 64941
> 49233  XX002 2016-12-05 23:06:44.087 PST:HINT:  Please REINDEX it.
> 49233  XX002 2016-12-05 23:06:44.087 PST:CONTEXT:  automatic vacuum of table
> "jjanes.public.foo"
>

Thanks for the report.  This can happen due to vacuum trying to access
a new page.  Vacuum can do so if (a) the calculation for maxbuckets
(in metapage) is wrong or (b) it is trying to free the overflow page
twice.  Offhand, I don't see that can happen in code.  I will
investigate further to see if there is any another reason why vacuum
can access the new page.  BTW, have you done the test after commit
2f4193c3, that doesn't appear to be the cause of this problem, but
still, it is better to test after that fix.  I am trying to reproduce
the issue, but in the meantime, if by anychance, you have a callstack,
then please share the same.

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

Commits

  1. Remove _hash_wrtbuf() in favor of calling MarkBufferDirty().

  2. Fix race introduced by 6d46f4783efe457f74816a75173eb23ed8930020.

  3. Improve hash index bucket split behavior.

  4. Reduce pinning and buffer content locking for btree scans.