Support for weak binding views to allow dropping of underlying objects

[R4hul04]

Description

Currently, Babelfish only supports strong binding for views, which prevents dropping or altering referenced objects when views depend on them. This behavior differs from SQL Server, which by default allows dropping underlying tables or views unless WITH SCHEMABINDING is explicitly specified.
With this change, Babelfish now supports configurable view binding modes:

1. Strong binding (default): Prevents dropping referenced objects if views depend on them
2. Weak binding: Allows dropping of referenced objects

This feature aligns Babelfish more closely with SQL Server's behavior, providing greater flexibility
Key aspects include:

• A new GUC parameter babelfishpg_tsql.weak_view_binding to control the default binding behavior (default is false)
• Support for explicit WITH SCHEMABINDING to create strongly bound views regardless of the GUC setting
• Ability to create weakly bound views by default when the GUC is enabled
• Proper handling of ALTER VIEW operations in both binding modes

In SQL Server, views are weakly bound by default, allowing underlying objects to be dropped or altered. With our implementation, users can now choose between SQL Server's default behavior (weak binding) or the previously enforced behavior (strong binding).

Important Limitation :

This implementation currently only addresses DROP operations on tables, views as well as ALTER operations on views. ALTER TABLE operations (such as dropping columns or changing data types) are still restricted when dependent views exist, regardless of binding mode. This differs from SQL Server's behavior, where weak binding also allows ALTER operations on referenced objects.

Issues Resolved

BABEL-1660

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 15571970545

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 361 of 422 (85.55%) changed or added relevant lines in 4 files are covered.
• 133 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.1%) to 75.569%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
contrib/babelfishpg_tsql/src/hooks.c	350	411	85.16%

Files with Coverage Reduction	New Missed Lines	%
contrib/babelfishpg_tsql/src/pltsql_coerce.c	133	86.5%

Totals
Change from base Build 15464616681:	0.1%
Covered Lines:	49178
Relevant Lines:	65077

---

💛 - Coveralls