Rick Otten <rottenwindfish@gmail.com> writes:
> At the moment it seems like when multiple temp spaces are available, the
> temp spaces are chosen in a 'round robin' or perhaps 'random' fashion. Is
> that true?
Yes, see fd.c's SetTempTablespaces and GetNextTempTableSpace.
There's no concept of different temp spaces having different performance
characteristics, and anyway we don't really have enough info to make
accurate predictions of temp space consumption. So it's hard to see the
planner doing this for you automagically.
regards, tom lane