Jeremy Harris <j...@wizmail.org> writes: > In ordered_set_startup() sorts are initialised in non-randomAccess mode > (tuplesort_begin_heap() and ~datum(), last argument).
> The use of tuplesort_skip_tuples() feels very like a random access to > me. I think it doesn't fail because the only use (and implementation) > is to skip forwards; if backwards were tried (as the interface permits) > external sorts would fail because multiple tapes are present for > FINALMERGE. Well, we certainly don't want to incur the overhead of randomAccess mode when we're not actually going to use it, so I'd resist changing the code in ordered_set_startup(). It's true that if tuplesort_skip_tuples() supported backwards skip, it would need to insist that randomAccess mode be enabled *when a backwards skip is used*. But such a feature is purely hypothetical ATM. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers