The remote transaction uses SERIALIZABLE isolation level when the local transaction has SERIALIZABLE isolation level; otherwise it uses REPEATABLE READ isolation level. This choice ensures that if a query performs multiple table scans on the remote server, it will get snapshot-consistent results for all the scans. A consequence is that successive queries within a single transaction will see the same data from the remote server, even if concurrent updates are occurring on the remote server due to other activities. That behavior would be expected anyway if the local transaction usesSERIALIZABLE or REPEATABLE READ isolation level, but it might be surprising for a READ COMMITTED local transaction. A future PostgreSQL release might modify these rules.
now It can be set to REPEATABLE READ or higher level，and can't be lower level.
We are try to connect to Greenplum database from PostgreSQL 9.3 beta2 via postgres_fdw, but the Greenplum Database does not support REPEATABLE READ transactions, can we specify other isolation leves?
