Andrew Dunstan <andrew@dunslane.net> writes:
> On 03/21/2012 10:47 AM, Alvaro Herrera wrote:
>> I disagree with there being zero interest ... the "order by random()"
>> stuff does come up occasionally.
> Presumably the reason that's not good enough is that is scans the whole
> table (as well as being non-portable)?
The reason I'm concerned about the implementation effort is precisely
that I'm afraid people will have high expectations for the intelligence
of the feature. If it's not materially better than you can get today
with "order by random()", it's not worth doing. That will mean for
example that it can't just be something we bolt onto seqscans and be
done with --- it'll need to interact with indexscans, maybe joins, etc
etc. And no shortcuts on the quality of the sampling, either.
regards, tom lane