fix(postgresql): fix TEIID error when getting postgresql cancellation token

[davemulford]

Using TEIID virtual databases (VDBs) in Superset requires the use of the postgres connector. In a previous update, cancelation tokens were added to allow a query to be stopped on the database server. This is a good thing, however it introduced a bug that disallowed the use of TEIID VDBs.

This change wraps the SELECT pg_backend_pid() query in a try-catch phrase, and returns None upon exception.

The error encountered in the Superset SQL Editor is:

superset.exceptions.SupersetErrorsException: [SupersetError(message="TEIID30068 The function 'pg_backend_pid()' is an unknown form.  Check that the function name and number of arguments is correct.
DETAIL:  org.teiid.jdbc.TeiidSQLException: TEIID30068 The function 'pg_backend_pid()' is an unknown form.  Check that the function name and number of arguments is correct.",
error_type=<SupersetErrorType.GENERIC_DB_ENGINE_ERROR: 'GENERIC_DB_ENGINE_ERROR'>, level=<ErrorLevel.ERROR: 'error'>, extra={'engine_name': 'PostgreSQL', 'issue_codes': [{'code': 1002, 'message': 'Issue 1002 - The database returned an unexpected error.'}]})]

SUMMARY

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[villebro]

LGTM, thanks for the fix!

[villebro]

Minor improvement proposal: is there a more specific exception type that we could be catching here?

[davemulford]

I can double-check and make the change. Thanks for the review!

[davemulford]

I've updated the PR comment with the error being raised. It's a superset.exceptions.SupersetErrorsException. Would you like me to catch that instead of the generic exception?

[villebro]

I've updated the PR comment with the error being raised. It's a superset.exceptions.SupersetErrorsException. Would you like me to catch that instead of the generic exception?

Really? I would have thought it's a psycopg2 or at least a SQLAlchemy exception, as I assume it's coming from the cursor call. But yeah, let's make it as specific as possible if it's not too much trouble.

[stale]

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