| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Deleting older versions in unique indexes to avoid page splits |
| Date: | 2020-10-21 15:25:20 |
| Message-ID: | CA+TgmoZeNPeUEs0HRHcyaJD0pv+nUzygOmJAwWd60624mjez9g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Oct 7, 2020 at 7:48 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> To be blunt: It may be controversial that we're accessing multiple
> heap pages while holding an exclusive lock on a leaf page, in the
> hopes that we can avoid a page split, but without any certainty that
> it'll work out.
That certainly isn't great. I mean, it might be not be too terrible,
because it's a leaf index page isn't nearly as potentially hot as a VM
page or a clog page, but it hurts interruptibility and risks hurting
concurrency, but if it were possible to arrange to hold only a pin on
the page during all this rather than a lock, it would be better. I'm
not sure how realistic that is, though.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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