On Wed, Jun 18, 2014 at 12:46 PM, Andres Freund <andres@2ndquadrant.com> wrote:
> On 2014-06-18 12:36:13 -0400, Robert Haas wrote:
>> > I actually don't think any of the discussions I was involved in had the
>> > externally visible version of replication identifiers limited to 16bits?
>> > If you are referring to my patch, 16bits was just the width of the
>> > *internal* name that should basically never be looked at. User visible
>> > replication identifiers are always identified by an arbitrary string -
>> > whose format is determined by the user of the replication identifier
>> > facility. *BDR* currently stores the system identifer, the database id
>> > and a name in there - but that's nothing core needs to concern itself
>> > with.
>>
>> I don't think you're going to be able to avoid users needing to know
>> about those IDs. The configuration table is going to have to be the
>> same on all nodes, and how are you going to get that set up without
>> those IDs being user-visible?
>
> Why? Users and other systems only ever see the external ID. Everything
> leaving the system is converted to the external form. The short id
> basically is only used in shared memory and in wal records. For both
> using longer strings would be problematic.
>
> In the patch I have the user can actually see them as they're stored in
> pg_replication_identifier, but there should never be a need for that.
Hmm, so there's no requirement that the short IDs are consistent
across different clusters that are replication to each other? If
that's the case, that might address my concern, but I'd probably want
to go back through the latest patch and think about it a bit more.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
