Gregory Stark <stark@enterprisedb.com> writes:
> ... it's kind
> of pie-in-the-sky since it depends on every column being toasted (and not
> compressed). It's much more normal to have some columns be quite large and
> others more normal sized or different data types.
Yeah. I think those numbers should simply be removed from the
discussion entirely, because they are bogus. There is no real-world
situation where someone is going to put 1Gb into each and every field of
a row. The limits that should be stated are 1Gb per column and 250-1600
columns per table --- let the readers draw their own conclusions from
those.
As Greg notes, the 400-column figure came from presuming that every
column gets toasted out-of-line; but that's not totally realistic
either. Furthermore, we have some untoastable types that are wider
than a toast pointer. The worst case seems to be 32 bytes for box,
line, and lseg (I ignore "name" which is stated not to be intended
for general-purpose use). If you made a table of only "box" columns
you could get at most a bit over 250 of them on a standard-size page.
So I think that's what we should quote as the lower bound.
regards, tom lane
