Disallow the use of user-defined functions in column defaults for temp tables and table variables.

[Sairakan]

Description

In SQL Server, it is prohibited for users to use user-defined functions as column defaults in temp tables and table variables - the only exception is in the tempdb database, but this is not currently even supported in Babelfish, so for now we will impose the same restrictions as exist elsewhere in SQL Server.

Issues Resolved

BABEL-4868

Test Scenarios Covered

• Use case based -

• Boundary conditions -

• Arbitrary inputs -

• Negative test cases -

• Minor version upgrade tests -

• Major version upgrade tests -

• Performance tests -

• Tooling impact -

• Client tests -

Check List

• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is under the terms of the Apache 2.0 and PostgreSQL licenses, and grant any person obtaining a copy of the contribution permission to relicense all or a portion of my contribution to the PostgreSQL License solely to contribute all or a portion of my contribution to the PostgreSQL open source project.

For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[coveralls]

Pull Request Test Coverage Report for Build 11846239624

Details

• 19 of 19 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.008%) to 74.729%

---

Totals
Change from base Build 11841522137:	0.008%
Covered Lines:	45649
Relevant Lines:	61086

---

💛 - Coveralls

[timchang514]

how expensive is this call? I think it should be fine assuming it's just syscache lookups, since this would only be called in very rare cases when we need to actually check a column default function on a temp table.

[Sairakan]

I don't know how expensive this call is, but as you said, this is buried below sufficient levels of checking that it shouldn't come up very often in the code path anyways. Basically, this would only get evaluated if we are dealing with a temp table using a function for a column default, and the function call is not schema-qualified. I suppose it could be made more efficient if we generated a list of all possible system functions and did a direct comparison against that list, but that seems like a lot of work.