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

On 2017-12-06 16:38:18 -0500, Todd A. Cook wrote:
> On 12/06/17 16:12, Andres Freund wrote:
> > 
> > > The datasets I shared are somewhat extreme in the sense that there are
> > > many contiguous sequences of hash values, but it only takes one such
> > > sequence with at least SH_GROW_MAX_MOVE values to trigger the issue. So
> > > the hash table may still be perfectly fine for most keys, and only
> > > slightly slower for the keys in the sequence.
> > 
> > Meh, we're talking about adversarial attacks here.
> 
> Hmmmmm...
> 
> I found this problem when I dropped 10.1 into a test environment to see
> what would happen.  There was no deliberate attempt to break anything.

Read Thomas' message at:
http://archives.postgresql.org/message-id/263b03b1-3e1c-49ca-165a-8ac6751419c4%402ndquadrant.com

Greetings,

Andres Freund