Re: Page Scan Mode in Hash Index

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Jesper Pedersen <jesper(dot)pedersen(at)redhat(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Page Scan Mode in Hash Index
Date: 2017-08-23 11:38:10
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On Tue, Aug 22, 2017 at 7:24 PM, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> wrote:
> On Tue, Aug 22, 2017 at 3:55 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> Okay, I got your point now. I think, currently in _hash_kill_items(),
> if an overflow page is pinned we do not check if it got modified since
> the last read or
> not. Hence, if the vacuum runs on an overflow page that is pinned and
> also has some dead tuples in it then it could create a problem for
> scan basically,
> when scan would attempt to mark the killed items as dead. To get rid
> of such problem, i think, even if an overflow page is pinned we should
> check if it got
> modified or not since the last read was performed on the page. If yes,
> then do not allow scan to mark killed items as dead. Attached is the
> newer version with these changes along with some other cosmetic
> changes mentioned in your earlier email. Thanks.

Thanks for the new version. I again looked at the patches and fixed
quite a few comments in the code and ReadMe. You have forgotten to
update README for the changes in vacuum patch
(0003-Improve-locking-startegy-during-VACUUM-in-Hash-Index_v7). I
don't have anything more to add. If you are okay with changes, then
we can move it to Ready For Committer unless someone else has some
more comments.

With Regards,
Amit Kapila.

Attachment Content-Type Size
0001-Rewrite-hash-index-scan-to-work-page-at-a-time_v13.patch application/octet-stream 31.8 KB
0002-Remove-redundant-hash-function-_hash_step-and-do-som.patch application/octet-stream 8.5 KB
0003-Improve-locking-startegy-during-VACUUM-in-Hash-Index_v7.patch application/octet-stream 7.8 KB

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