| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Kevin Grittner <kgrittn(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Alik Khilazhev <a(dot)khilazhev(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: LP_DEAD hinting and not holding on to a buffer pin on leaf page (Was: [WIP] Zipfian distribution in pgbench) |
| Date: | 2017-07-31 18:51:27 |
| Message-ID: | CA+TgmoYMEJKaE5A92ODeEXxXxNrp7d=n3EHM6HcFScEJNL92zw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Jul 31, 2017 at 1:54 PM, Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> That is hard to justify. I don't think that failing to set LP_DEAD hints
> is the cost that must be paid to realize a benefit elsewhere, though. I
> don't see much problem with having both benefits consistently. It's
> actually very unlikely that VACUUM will run, and a TID will be recycled
> at exactly the wrong time. We could probably come up with a more
> discriminating way of detecting that that may have happened, at least
> for Postgres 11. We'd continue to use LSN; the slow path would be taken
> when the LSN changed, but we do not give up on setting LP_DEAD bits. I
> think we can justify going to the heap again in this slow path, if
> that's what it takes.
Yeah, that might possibly be a good approach.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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