Re: [PATCH] postgres_fdw extension support

On 2015-07-22 14:55:15 -0400, Tom Lane wrote:
> Just to be clear here: the case we are concerned about is, given that
> we have determined that function X is or is not a member of one of the
> extensions marked "shippable" for a given connection, is it likely that
> that status will change (while the function continues to exist with
> the same OID) during the lifespan of the connection? If it did change,
> how critical would it be for us to honor the new shippability criterion
> on that connection? My answer to both is "not very". So I'm not excited
> about expending lots of code or cycles to check for such changes.

It doesn't seem that unlikely that somebody does an ALTER SERVER OPTIONS
SET .. to add an extension to be shippable while connections are already
using the fdw. It'll be confusing if some clients are fast and some
others are really slow.

I think we should at least add invalidations for changing server
options. I think adding support for extension upgrades wouldn't hurt
either. Not particularly excited to ALTER EXTENSION ADD, but we could
add it easy enough.

> If we were trying to cache things across more than a connection lifespan,
> the answer might be different.

I think connection poolers defeat that logic more widely tha nwe
sometimes assume.

- Andres