| From: | "Todd A(dot) Cook" <tcook(at)blackducksoftware(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, PostgreSQL Bugs <pgsql-bugs(at)postgresql(dot)org> |
| Subject: | Re: BUG #14932: SELECT DISTINCT val FROM table gets stuck in an infinite loop |
| Date: | 2018-01-30 18:57:44 |
| Message-ID: | 039b8fa5-8272-8b14-3710-926de5844677@blackducksoftware.com |
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| Lists: | pgsql-bugs |
On 01/29/18 14:26, Andres Freund wrote:
> On 2018-01-29 13:56:37 -0500, Todd A. Cook wrote:
>> With those patches applied, I'm able to process a 175 million row data set
>> without any problems.
>
> Cool!
>
>> I'll try the 900 million row set next.
We're also able to process those 900 million rows without problems. :)
It took about 28 minutes (average of 3 runs).
Out of curiosity, I then modified hashint8() as previously described.
With that change, run time dropped to 11 minutes (also average of 3
runs).
FWIW, the data values in these sets are sort-of random (where I can't
explain the "sort-of" in a public forum), but strongly biased towards
negative infinity. Starting again from scratch, we could probably remove
the bias, but we have 28-30 billion of these things collected over the
last 14 years (starting in PostgreSQL 7.4) and it's kinda tough to change
directions at this point...
-- todd
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