Re: lazy detoasting

On 04/10/18 00:30, Andrew Gierth wrote:

> That's not precisely true - ultimately, the routines that do actual
> scans take the snapshot to use as a parameter, and the executor mostly
> references the snapshot from the EState; but a bunch of places do
> require that ActiveSnapshot be set to the currently applicable snapshot
> (e.g. for queries inside stable functions nested inside the main query).

I'm becoming increasingly glad I asked (or less embarrassed that I hadn't
figured it all out yet).  :)

Am I right in thinking that, for my original purpose of detoasting something
later in a transaction, all that matters is that I registered a snapshot
from the time at which I copied the toasted datum, and the resource owner
I registered it to has not been released yet, so rows referred to in the
snapshot haven't been vacuumed away? Is that a sufficient condition for
detoast to work?

Or would I need to do something more, like push and pop that snapshot
around the detoast call?

This would be in a PL function (or the handler for the PL function),
if the context matters.

-Chap