Re: Modifying TOAST thresholds

Bruce Momjian <bruce(at)momjian(dot)us> writes:
> Simon Riggs wrote:
>> Having both default GUC and individual table-level WITH parameters seems
>> like the best way to me.

> Agreed.

There's an extremely good reason not to have a GUC variable, which is
that changes in it would fail to reflect into decisions about whether to
create TOAST tables. When I first brought up the point I didn't see a
way around it, but now that I do, I don't think we should expose a
failure mode just to have a GUC.

> OK, but we need to throw a clear message when the TOAST table needs to
> be created by the administrator.

No, we just need to not have a GUC for this. There's no GUC for default
fill factor; have you seen anyone complain about that?

> The big question is whether this is for 8.3 or 8.4.

What I would definitely like to see for 8.3 is some performance testing
done to determine whether we ought to change the current defaults.
(Both TOAST_TUPLES_PER_PAGE and EXTERN_TUPLES_PER_PAGE ought to be looked
at.)

Whether it's possible to get the storage parameter in there depends on
how soon someone produces a patch. Given that we understand this area
fairly well, I personally would be willing to give it a pass on the
"feature freeze" rule, as long as we have the patch by say mid-April.

regards, tom lane