I wrote: > "ldh@xxxxxxxxxxxxxxxxxx" <ldh@xxxxxxxxxxxxxxxxxx> writes: >> It's still spilling to disk and seems to cap at 2.5GB of memory usage in spite of configuration. > That is ... weird. Oh: see get_hash_mem: hash_mem = (double) work_mem * hash_mem_multiplier; /* * guc.c enforces a MAX_KILOBYTES limitation on work_mem in order to * support the assumption that raw derived byte values can be stored in * 'long' variables. The returned hash_mem value must also meet this * assumption. * * We clamp the final value rather than throw an error because it should * be possible to set work_mem and hash_mem_multiplier independently. */ if (hash_mem < MAX_KILOBYTES) return (int) hash_mem; return MAX_KILOBYTES; So basically, we now have a hard restriction that hashaggs can't use more than INT_MAX kilobytes, or approximately 2.5GB, and this use case is getting eaten alive by that restriction. Seems like we need to do something about that. regards, tom lane
