Peter T Mount <peter@retep.org.uk> writes:
> Quoting Joe Conway <joseph.conway@home.com>:
>> indicating that the practical limit is closer to 1 GB -- not sure why).
> It may be something to do with the 1Gb splitting of the physical files
> representing a table...
No, that's just a coincidence. The reason that TOAST limits fields to
1Gb is that the high-order two bits of the varlena length word were
commandeered as TOAST state indicators. There are now only thirty bits
available to represent the length of a variable-length Datum; hence the
hard limit on field width is 1Gb.
I'd think that the "practical" limit is quite a bit less than that, at
least until we devise an API that lets you read and write toasted values
in sections.
regards, tom lane