Remote troubleshooting session connection?

I'm working on an ETL system that is driven from Java/JDBC but is implemented mostly as SQL queries against a PostgreSQL database.

An ETL "job" runs inside its own transaction and consists of a series of queries that transform the data from staging tables to the destination tables. If a failure occurs, the transaction rolls back so there's no "debris" left over -- which makes troubleshooting very difficult.

In the Java world we have JPDA, which allows us to connect to a running JVM to examine the state of variables and set breakpoints, etc.

Assuming I can pause the driving Java code between queries in a job, is there any way to connect from PGAdmin (or another tool) and view the state of tables in the in-progress transaction? If this is not currently possible, how difficult would it be to do?