Simply, what version of Postgres is supported? (when selecting client drivers)

I recently encountered a number of metadata query errors when attempting to connect to Cockroach with a third party data modelling tool. One of the issues related to the pg_catalog.pg_am table, not having an expected column. I think this is a known issue that is being addressed.

However, my question remains. For a given release of Cockroach, can we please get a recommended version of Postgres for driver compatibility when connecting with other tools?

For issues with the pg_am table, please see if https://github.com/cockroachdb/cockroach/issues/32624 corresponds to your problem.

The CRDB server identifies itself as Postgres 9.5 to clients. This is not something that the client application can control. However, to the extent that a client can choose anything, it should probably choose 9.5 as that’s what most people use.
I believe there aren’t particular reasons for 9.5; I don’t think we’re more or less compatible with 9.5 than with other versions (we might be more compatible in some ways and less in others).
@knz might know more.

Thanks Andrei.
Sadly, the issue I have is due to the fact that CRDB is claiming to be PG 9.5, but does not implement some of its system tables correctly. Perhaps if CRDB presented itself as 9.6, this would not be a problem. In any case, it looks like there is work being done on this issue.
The issue you referenced is one that I am following with great interest. As a matter of fact, it looks like a fix is coming soon in https://github.com/cockroachdb/cockroach/pull/33252, but I’m not exactly sure how to tell when/where that is available.

Also, and this may be more of a Postgres question, do you know how to query the PG version from CRDB?
Thanks.

As others have said, cockroachdb announces pg 9.5 compatibility but was actually incorrectly doing so, because of the problem you’ve identified.

We have implemented a solution:

Yes this will fix your problem and will be released in an upcoming 2.1.x release. Check out the release notes.

how to query the PG version from CRDB? Thanks.

SHOW server_version in SQL.