Re: BUG #14932: SELECT DISTINCT val FROM table gets stuck in an infinite loop

Todd A. Cook <tcook@blackducksoftware.com>

From: "Todd A. Cook" <tcook@blackducksoftware.com>

To: Andres Freund <andres@anarazel.de>

Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>, <pgsql-bugs@postgresql.org>

Date: 2017-11-28T14:49:34Z

Lists: pgsql-bugs

On 11/27/17 17:10, Andres Freund wrote:
> Hi,
> 
> On 2017-11-27 15:59:37 -0500, Todd A. Cook wrote:
>> COPY reproducer (val) FROM stdin;
>> 2976219712004784288
>> -6429122065899879392
>> -7471109962990387136
>> -7471109962990387136
>> -2895470491222113184
>> -4083509061952565472
>> 1019481548263425664
>> 4639248884787347648
>> -6999443831165647744
>> -4199917803455020480
>> -4110530183001439680
> 
> How are these values generated? They awfully look like hash values
> (~same lenght, full numerical range)...

They are biased hashes.  FWIW, the reproducer data is from one column of a
three-column primary key.

-- todd

Commits

Improve bit perturbation in TupleHashTableHash.
- d18d4bca81f8 10.2 landed
- c068f87723ca 11.0 landed
Prevent growth of simplehash tables when they're "too empty".
- d1aac2998789 10.2 landed
- ab9f2c429d8f 11.0 landed
Add stack-overflow guards in set-operation planning.
- 1b2a3860d3ea 10.2 cited