| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
| Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, Japin Li <japinli(at)hotmail(dot)com>, Zhihong Yu <zyu(at)yugabyte(dot)com>, Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Daniel Westermann <dwe(at)dbi-services(dot)com>, Erik Rijkers <er(at)xs4all(dot)nl>, Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec>, Andres Freund <andres(at)anarazel(dot)de> |
| Subject: | Re: Should use MERGE use BulkInsertState ? |
| Date: | 2022-05-13 16:20:43 |
| Message-ID: | CA+TgmobC6RD2N8kbPPTvATpUY1kisY2wJLh2jsg=HGoCp2RiXw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, May 11, 2022 at 12:48 PM Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> The point of the ring/strategy buffer is to avoid a seq scan/vacuum/COPY
> clobbering the entire buffer cache when processing a table larger than
> shared_buffers.
>
> It also makes backends doing bulk operations responsible for their own writes,
> rather than leaving other backends to clean up all their dirty buffers.
Right. It's not just about how fast individual operations go: dirtying
all of shared_buffers is faster *for you* but you've imposed a
distributed cost on everyone else on the system, which isn't great.
That said, I'm not really sure what the proper handling is in this
specific case. I guess we should try our best to have it be symmetric
with other similar cases, but questions have been raised repeatedly
about how well the ring buffer stuff actually works.
--
Robert Haas
EDB: http://www.enterprisedb.com
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