fix: Remove DDL automatically issued by Ibis for Postgres connections

[nehanene15]

Closes #1035

• Overwrites PG do_connect() method to remove CREATE FUNCTION DDL automatically issued by Ibis (here)

[nehanene15]

/gcbrun

[nj1973]

Should we add an integration test to run test_postgres.py against a read replica? Not for this PR, thinking if we need a new issue for that or if it is overkill?

[nj1973]

That looks much better to me. Because the code was creating the functions on every execute we would generate a lot of warnings if we went down the isolation_level route I was investigating.

Aside from my comment about tests your changes LGTM.

[sundar-mudupalli-work]

Neil, This fix did not work on spanner postgres adapter. Here is some further information Researching the issue with the pgadapter, the notes on Ibis 6.0.0 says ``` - *postgres:* Ibis no longer automatically defines first/last reductions on connection to the postgres backend. Use DDL shown in https://wiki.postgresql.org/wiki/First/last_(aggregate) or one of the pgxn implementations instead.` in https://github.com/ibis-project/ibis/releases. - ```Might upgrading to 6.0 (or later) help us - it may be a lot of work though.

…

On Wed, Dec 6, 2023, 1:36 AM Neil Johnson ***@***.***> wrote: ***@***.**** commented on this pull request. Should we add an integration test to run test_postgres.py against a read replica? Not for this PR, thinking if we need a new issue for that or if it is overkill? — Reply to this email directly, view it on GitHub <#1067 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AZK36WPNYHEBPTGJEIOASS3YIA4ADAVCNFSM6AAAAABAIIY2SSVHI2DSMVQWIX3LMV43YUDVNRWFEZLROVSXG5CSMV3GSZLXHMYTONRXGEYDCNRVHA> . You are receiving this because your review was requested.Message ID: <GoogleCloudPlatform/professional-services-data-validator/pull/1067/review/1767101658 @github.com>

[nehanene15]

Should we add an integration test to run test_postgres.py against a read replica? Not for this PR, thinking if we need a new issue for that or if it is overkill?

I don't think we need a test for a read replica since the Ibis upgrade get's rid of the DDL in v6.0 anyways. But if another similar issue comes up, we can consider it. Thanks for the review!