Re: Conflict Detection and Resolution - Mailing list pgsql-hackers

On Tue, Oct 1, 2024 at 9:48 AM shveta malik <shveta.malik@gmail.com> wrote:
>
> On Mon, Sep 30, 2024 at 2:55 PM Peter Smith <smithpb2250@gmail.com> wrote:
> >
> > On Mon, Sep 30, 2024 at 4:29 PM shveta malik <shveta.malik@gmail.com> wrote:
> > >
> > > On Mon, Sep 30, 2024 at 11:04 AM Peter Smith <smithpb2250@gmail.com> wrote:
> > > >
> > > > On Mon, Sep 30, 2024 at 2:27 PM shveta malik <shveta.malik@gmail.com> wrote:
> > > > >
> > > > > On Fri, Sep 27, 2024 at 1:00 PM Peter Smith <smithpb2250@gmail.com> wrote:
> > > > >
> > > > > > ~~~
> > > > > >
> > > > > > 14.
> > > > > > 99. General - ordering of conflict_resolver
> > > > > >
> > > > > > nit - ditto. Let's name these in alphabetical order. IMO it makes more
> > > > > > sense than the current random ordering.
> > > > > >
> > > > >
> > > > >  I feel ordering of resolvers should be same as that of conflict
> > > > > types, i.e. resolvers of insert variants first, then update variants,
> > > > > then delete variants. But would like to know what others think on
> > > > > this.
> > > > >
> > > >
> > > > Resolvers in v14 were documented in this random order:
> > > > error
> > > > skip
> > > > apply_remote
> > > > keep_local
> > > > apply_or_skip
> > > > apply_or_error
> > > >
> > >
> > > Yes, these should be changed.
> > >
> > > > Some of these are resolvers for different conflicts. How can you order
> > > > these as "resolvers for insert" followed by "resolvers for update"
> > > > followed by "resolvers for delete" without it all still appearing in
> > > > random order?
> > >
> > > I was thinking of ordering them like this:
> > >
> > > apply_remote:              applicable to insert_exists, update_exists,
> > > update_origin_differ, delete_origin_differ
> > > keep_local:                   applicable to insert_exists,
> > > update_exists,  update_origin_differ, delete_origin_differ
> > > apply_or_skip:              applicable to update_missing
> > > apply_or_error :            applicable to update_missing
> > > skip:                              applicable to update_missing and
> > > delete_missing
> > > error:                             applicable to all.
> > >
> > > i.e. in order of how they are applicable to conflict_types starting
> > > from insert_exists till delete_origin_differ  (i.e. reading
> > > ConflictTypeResolverMap, from left to right and then top to bottom).
> > > Except I have kept 'error' at the end instead of keeping it after
> > > 'keep_local' as the former makes more sense there.
> > >
> >
> > This proves my point because, without your complicated explanation to
> > accompany it, the final order (below) just looks random to me:
> > apply_remote
> > keep_local
> > apply_or_skip
> > apply_or_error
> > skip
> > error
> >
> > Unless there is some compelling reason to do it differently, I still
> > prefer A-Z (the KISS principle).
> >
>
> The "applicable to conflict_types" against each resolver (which will
> be mentioned in doc too) is a pretty good reason in itself to keep the
> resolvers in the suggested order.  To me, it seems more logical than
> placing 'apply_or_error' which only applies to the 'update_missing'
> conflict_type at the top, while 'error,' which applies to all
> conflict_types, placed in the middle. But I understand that
> preferences may vary, so I'll leave this to the discretion of others.
>

In v15, I maintained the original order of conflict_resolver, which to
me seems reasonable from a user perspective:
error
skip
apply_remote
keep_local
apply_or_error
apply_or_skip

I will hold this order until we receive feedback from others, and we
can finalize the new order if necessary.

Thanks,
Nisha