Jeff Adams <jeff(dot)adams(at)noaa(dot)gov> writes:
> I have a very large table (approximately 1 billion records). I need to
> change a field's data type from integer to bigint. I started up an ALTER
> TABLE approach yesterday and it is still running (trying to rewrite the
> whole table?). I remember seeing mention of being able to do this in the
> pg_attribute table. Has anybody ever used the latter approach. If so,
> instructions would be greatly appreciated. Thanks...
No, that is an actual on-disk change (making the field physically
wider), so it's going to cost ya. There are some cases where the
on-disk representation doesn't change and so a catalog update isn't
needed, but int4->int8 isn't one of them.
regards, tom lane