| From: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, y(dot)sokolov(at)postgrespro(dot)ru, Peter Geoghegan <pg(at)bowt(dot)ie>, Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, "Ideriha, Takeshi" <ideriha(dot)takeshi(at)jp(dot)fujitsu(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com>, pgsql-hackers-owner(at)postgresql(dot)org |
| Subject: | Re: [HACKERS] GUC for cleanup indexes threshold. |
| Date: | 2017-11-29 15:06:25 |
| Message-ID: | CAD21AoAt-qrrRQn0_2sLgV=QGEwaecPRn0ypSGBhoWTt7K59xg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Nov 29, 2017 at 11:05 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On 25 September 2017 at 22:34, Kyotaro HORIGUCHI
> <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>
>>> > Here is a small patch that skips scanning btree index if no pending
>>> > deleted pages exists.
>>> > It detects this situation by comparing pages_deleted with pages_free.
>>
>> It seems to work to prevent needless cleanup scans.
>
> So this leaves us in the situation that
>
> 1. Masahiko's patch has unresolved problems
> 2. Yura's patch works and is useful
>
> Unless there is disagreement on the above, it seems we should apply
> Yura's patch (an edited version, perhaps).
>
IIRC the patches that makes the cleanup scan skip has a problem
pointed by Peter[1], that is that we stash an XID when a btree page is
deleted, which is used to determine when it's finally safe to recycle
the page. Yura's patch doesn't have that problem?
Regards,
--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
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