Samuel Gendler <sgendler@ideasculptor.com> writes:
> Answered my own question. Cranking work_mem up to 350MB revealed that
> the in-memory sort requires more memory than the disk sort.
Yeah. The on-disk representation of sortable data is tighter than the
in-memory representation for various reasons, mostly that we're willing
to work at making it small. Datums aren't necessarily properly aligned
for example, and there's also palloc overhead to consider in-memory.
regards, tom lane