pq2jdbc is bridge between PostgreSQL libpq client and any JDBC-compatible database.
It's java application, which should be started on some port and simulate Postgres server.
It connects through JDBC driver to any JDBC-compatible database, redirects libpq requests
to it and receives replies.

Why it is needed?
The primary goal of this application was to provide access from Postgres
to HIVE and Apache Ignite. There is Postgres JDBC FDW https://github.com/atris/JDBC_FDW
but it has the following limitations:
1. It is read-only and doesn't support updates.
2. It establishes new connection on each query, so speed is awful.

Certainly it is possible to impalement improved version of this FDW.
But development of good FDW (supporting index scans, push-downs, ...) is quite sophisticated task.
The idea was to use postgres_fdw and connect through pq2jdbc bridge to any JDBC-compatible database.

Another use case (not sure how useful it is) is to allow postgres unities and clients to access another
databases. For example it is possible to use pgbench to benchmark mySQL or Oracle.

If somebody find another use cases for this application, please let me know:)

How to use?
First of all you need to get JDBC driver for the target database.
Then launch pq2jdbc like this

   java -cp pq2jdbc.jar:postgresql-42.1.4.jar ru.postgrespro.pq2jdbc.Main -v -t

Supported options are:
	-v	    verbose mode
	-t	  	translate Postgres specific commands
	-p PORT	server port (default: 5432)
	-c URL  JDBC URL (default: "postgresql:")
	-d URL  JDBC driver (default: "org.postgresql.Driver")


-t option makes pq2jdbc to translated PostgreSQL specific commands (transactio control, cursor manipulation,...) to standard SQL commands.
In verbose mode pq2jdbc display all executed commands.