Re: [Postgres-xc-general] work with foreign-data wrapper

[鈴木 幸市 <ko...@in...>]

Yes, foreign data is not a part of XC cluster.   Foreign data's transaction management is separate from the cluster and we cannot enforce data integrity.   Even though we support FDW, it is just foreign data, not a part of XC cluster.   To make PostgreSQL data as a part of XC cluster, PG needs to accept GXID and snapshot from XC, as well as sequence, if it is shared with other tables in XC.

It does not sound simple because in this case, PostgreSQL database is not autonomous and cannot operate by its own.

Regards;
---
Koichi Suzuki

On 2013/10/17, at 14:52, Amit Khandekar <ami...@en...<mailto:ami...@en...>>
 wrote:

I think Aris's expectation is that by using FDW support we can create a cluster of heterogeneous nodes. This is not going to happen just by supporting  foreign data wrappers and foreign tables.

Note that allowing a foreign table/server to be created in Postgres-XC means a foreign table will be created on a machine which is completely outside the Postgres-XC cluster. Making that machine a part of the cluster is a different thing, and that does not require FDWs.


On 17 October 2013 10:48, 鈴木 幸市 <ko...@in...<mailto:ko...@in...>> wrote:
So far, CREATE FOREIGN DATA WRAPPER, CREATE SERVER and CREATE USER MAPPING are blocked.   As Michael suggests, yes, it would be nice to connect to foreign data through coordinators or even datanodes.

It's welcome if more people are involved in the test, not just development.   Contribution of the code is more than welcome.

Unfortunately, nobody dis these work mainly due to the resource.   it will be wonderful if anybody can join and contribute the code.   There are not reason that XC doesn't have to support FDW.

Best;
---
Koichi Suzuki

On 2013/10/17, at 13:11, Michael Paquier <mic...@gm...<mailto:mic...@gm...>> wrote:

> On Thu, Oct 17, 2013 at 12:43 PM, Aris Setyawan <ari...@gm...<mailto:ari...@gm...>> wrote:
>> Hi,
>>
>> Can XC be used with [write-able] foreign-data wrapper? What I mean
>> here are push down optimization and data distribution.
> XC does not support itself fdw, but I don't see why there would be
> problems to have a Postgres server with a postgres_fdw connect to
> Coordinators for read/write operations or even Datanodes for read-only
> operations as the communication interface is the same as vanilla. Take
> care to use at least XC 1.1~ for the latter though.
>
>> I imagine, If yes, we can have a cluster of not just postgresql node.
>> But we can have oracle or mysql or redis or unlimited cluster.
> Yep. Supporting FDW in XC would be fun as well. Patches welcome.
> --
> Michael
>
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