Re: Savepoints in plpgsql

On Thursday, July 11, 2024, PG Doc comments form <noreply(at)postgresql(dot)org>
wrote:

> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/16/plpgsql-transactions.html
> Description:
>
> https://www.postgresql.org/docs/current/plpgsql-transactions.html
>
> In this section nothing mentioned that a savepoint (a subtransaction) will
> not work inside plpgsql.

>
Correct, we prefer to just document how things work. 43.2 does mention
that blocks form subtransactions.

Also need to say, that "begin
> end" block with "exception" handler will implicitly save and release
> savepoints.
>

A savepoint is an SQL command giving you access to subtransactions.
Plpgsql doesn’t need or use it, it has a direct access to subtransactions
though in a limited/different way. In short, even if this worked this way
we wouldn’t document such an implementation detail.

I suppose we could draw analogies to savepoints, or maybe mention
subtransactions again in the procedure transactions chapter. Namely by
explaining why the last limitation on that page exists, which I presume is
related to subtransactions. But really that page is meant to show how
procedures can use commit/rollback to anffect the outer transaction unlike
all other plpgsql code which simply gets block-based subtransactions
management as previously described. It does this sufficiently and need not
be cluttered by subtransaction discussion in any meaningful detail.

David J.