Transaction control in shards through PLPROXY

Hi,

Even though this mailing list is for postgresql users only, I am sending this query 

related to postgresql sharding in case anyone has already faced this problem while 

sharding their database. 

Inspite of being aware that PLPROXY does autocommit for DML functions called
on shards, I was wondering if there is any way around to put a set of DML
functions called from Router on shards inside a transaction so that all
updates on shards can be rolled back if any one among the set fails?

It would be great if anyone has already done this in their sharded database.
I was looking into transaction manager but it handles only one DML function
at a time.

Many Thanks,
GB