Re: Function to move the position of a replication slot

On 2017-08-16 17:06:42 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2017-08-16 12:24:11 -0400, Peter Eisentraut wrote:
> >> On 5/4/17 08:05, Magnus Hagander wrote:
> >>> PFA a patch that adds a new function, pg_move_replication_slot, that
> >>> makes it possible to move the location of a replication slot without
> >>> actually consuming all the WAL on it.
>
> >> The name keeps confusing me. I understand "move" to be "rename" or
> >> possibly "move it elsewhere", but not "move around in". I understand
> >> that there is an analogy with FETCH/MOVE in cursors, but it's still
> >> confusing.
>
> > pg_forward_replication_slot()?
>
> If I understand what this is meant to do, maybe better
> pg_move_replication_slot_lsn() or pg_change_replication_slot_lsn() ?
> The point being that you're adjusting the LSN pointer contained
> in the slot, which is distinct from the slot itself.

I think we should constrain the API to only allow later LSNs than
currently in the slot, rather than arbitrary ones. That's why I was
thinking of "forward". I'm not convinced it's a good / safe idea to
allow arbitrary values to be set.

Greetings,

Andres Freund