On Mon, Nov 7, 2016 at 8:40 AM, Shay Rojansky <r...@roji.org> wrote:

> >     1. Does everyone agrees that renaming the existing datatype without
>> >     changing the OID?
>> >
>> >
>> > As I said before, Npgsql for one loads data types by name, not by OID.
>> > So this would definitely cause breakage.
>> Why would that cause breakage?
> Well, the first thing Npgsql does when it connects to a new database, is
> to query pg_type. The type names are used to associate entries with type
> handlers, avoiding the hard-coding of OIDs in code. So if the type name
> "macaddr" suddenly has a new meaning and its wire representation is
> different breakage will occur. It is possible to release new versions of
> Npgsql which will look at the PostgreSQL version and say "we know that in
> PostgreSQL < 10 macaddr means this, but in >= 10 it means that". But that
> doesn't seem like a good solution, plus old versions of Npgsql from before
> this change won't work.

The new datatype that is going to replace the existing one works with both
6 and 8 byte
MAC address and stores it a variable length format. This doesn't change the
wire format.
I don't see any problem with the existing applications. The new datatype
can recv and send
8 byte MAC address also.

Hari Babu
Fujitsu Australia

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