[postgres-xl-bugs] Postgres-XL does not support FOREIGN DATA WRAPPER

Tomas Vondra tomas.vondra at 2ndquadrant.com
Tue Oct 17 03:02:57 PDT 2017


Hi,

On 10/17/2017 05:13 AM, zhangjin wrote:
> Hi
> 
> postgres=# create extension dblink;
> ERROR:  Postgres-XL does not support FOREIGN DATA WRAPPER yet
> DETAIL:  The feature is not currently supported
> 

Right, FDWs are not supported, as is clearly indicated by the error
message. So this is expected behavior, not a bug. We could do a better
job in documenting it, though.

In the future, please either send similar questions to
postgres-xl-general, or explain why you think the behavior is a bug.

The reasons why this is not supported currently is that we don't have a
good way to implement this in multi-node systems (we'd probably have to
define and open the FDW connection on every node, and it's not clear if
each node should communicate with the target database independently, or
synchronize access somehow.

For example for cstore_fdw we'd like independent execution (as each node
will have local cstore_fdw storage), while for access to separate
databases we probably need to share the connection somehow (otherwise
can end up opening many connections to the remote system).



regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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