| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, David Hinkle <hinkle(at)cipafilter(dot)com> |
| Subject: | Re: Avoiding OOM in a hash join with many duplicate inner keys |
| Date: | 2017-02-16 19:37:38 |
| Message-ID: | CAH2-WznjYJfHmXq4O12Fbb3nVkQZYU9oaoMWuVMzDwEOg7sSmw@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Thu, Feb 16, 2017 at 11:11 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> I do think that's worrying, but on the other hand it seems like this
> solution could disable many hash joins that would actually be fine. I
> don't think the largest ndistinct estimates we ever generate are very
> large, and therefore this seems highly prone to worry even when
> worrying isn't really justified.
+1. ndistinct has a general tendency to be wrong, owing to how ANALYZE
works, which we see problems with from time to time.
--
Peter Geoghegan
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Tom Lane | 2017-02-16 19:38:19 | Re: Avoiding OOM in a hash join with many duplicate inner keys |
| Previous Message | Robert Haas | 2017-02-16 19:11:23 | Re: Avoiding OOM in a hash join with many duplicate inner keys |