Re: MAIN vs. PLAIN

"Dave Held" <dave.held@arrayservicesgrp.com> writes:
> I notice that by default, postgres sets numeric fields to
> storage MAIN.  What exactly does that mean?

See http://developer.postgresql.org/docs/postgres/storage-toast.html

There isn't any amazingly strong reason why numeric defaults to MAIN
rather than EXTENDED, which is the default for every other toastable
datatype --- except that I thought it'd be a good idea to have at
least one type that did so, just to exercise that code path in the
tuple toaster.  And numeric shouldn't ordinarily be large enough to
need out-of-line storage anyway.  It's unlikely even to need
compression, really, but as long as it's a varlena type the overhead
to support toasting is nearly nil.

            regards, tom lane