Re: [HACKERS] Avoiding OOM in a hash join with many duplicate inner keys - Mailing list pgsql-hackers

From Peter Geoghegan
Subject Re: [HACKERS] Avoiding OOM in a hash join with many duplicate inner keys
Date
Msg-id CAH2-WznjYJfHmXq4O12Fbb3nVkQZYU9oaoMWuVMzDwEOg7sSmw@mail.gmail.com
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In response to Re: [HACKERS] Avoiding OOM in a hash join with many duplicate inner keys  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On Thu, Feb 16, 2017 at 11:11 AM, Robert Haas <robertmhaas@gmail.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



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