| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Richard Guo <guofenglinux(at)gmail(dot)com> |
| Cc: | Paul George <p(dot)a(dot)george19(at)gmail(dot)com>, Andy Fan <zhihuifan1213(at)163(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Eager aggregation, take 3 |
| Date: | 2024-08-29 12:40:09 |
| Message-ID: | CA+TgmoYdO68GtU9WZ1_a+gJs7fZ96sNraxyvVwu4iRYv4kYmLQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Aug 28, 2024 at 10:26 PM Richard Guo <guofenglinux(at)gmail(dot)com> wrote:
> Yeah, I'm concerned about this too. In addition to the inaccuracies
> in aggregation estimates, our estimates for joins are sometimes not
> very accurate either. All this are likely to result in regressions
> with eager aggregation in some cases. Currently I don't have a good
> answer to this problem. Maybe we can run some benchmarks first and
> investigate the regressions discovered on a case-by-case basis to better
> understand the specific issues.
While it's true that we can make mistakes during join estimation, I
believe aggregate estimation tends to be far worse.
--
Robert Haas
EDB: http://www.enterprisedb.com
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