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 think that it's possible that a small number of users will find it > useful to set the value of hash_mem_multiplier as high as 5.0. That is > a very aggressive value, but one that could still make sense with > certain workloads.
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. Another point is that if you specify a unit for the multiplier (which is what users are likely to do for larger values), it'll fail anyway, so I'm not sure this is such terrible a problem. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
