Is there a PostgreSQL proxy running queries on several servers at once?

Question

Let's assume we had PostgreSQL version X.Y and decided to give a test-try to version Z.W. Probably, there are some changes between X.Y and Z.W that could cause a little bit of trouble :-)

It would be preferable to run Z.W in parallel with X.Y, checking whether it goes well and using only X.Y's replies for a while. Later on, having Z.W's DB "ok" we could use it as primary, discarding X.Y optionally.

Question: Is there any PostgreSQL proxy that can run queries on several servers at once?

Answer 1

first, you should check this post about common problems in version changes http://blog.endpoint.com/2010/01/postgres-upgrades-ten-problems-and.html

there is a tool named DBLink in postgreSQL, it is possible to create triggers and link them to Z.W version using dbLink and check if everything is ok.

another option you can run paralel queries on both servers and watch logs. but this can be possible on application side.

and also there is 3rd. party tool named pl/proxy http://wiki.postgresql.org/wiki/PL/Proxy

Answer 2

I dont know of any such proxy, but if the intent is to check that all statements processed by server1 are valid on server2 also, then you should consider the tools like pgreplay, etc.

See http://wiki.postgresql.org/wiki/Statement_Playback