Re: Default setting for enable_hashagg_disk

Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> On 2020-Jul-10, Peter Geoghegan wrote:
>> * The maximum allowable value is 100.0, to protect users from
>> accidentally setting hash_mem_multiplier to a value intended to work
>> like a work_mem-style KB value (you can't provide an absolute value
>> like that directly). This maximum is absurdly high.

> I'm not sure about this bit; sounds a bit like what has been qualified
> as "nannyism" elsewhere. Suppose I want to give a hash table 2GB of
> memory for whatever reason. If my work_mem is default (4MB) then I
> cannot possibly achieve that without altering both settings.
> So I propose that maybe we do want a maximum value, but if so it should
> be higher than what you propose. I think 10000 is acceptable in that it
> doesn't get in the way.

I was kind of thinking 1000 as the limit ;-). In any case, the code
will need to internally clamp the product to not exceed whatever the
work_mem physical limit is these days.

regards, tom lane