Refactor sys.columns_internal for improved performance

[rohit01010]

Description

The sys.columns_internal was originally implemented as a function, which caused significant performance bottleneck when used by dependent system views like sys.columns, sys.computed_columns, sys.identity_columns, and sys.syscolumns. Function scans prevent filter pushdown and force the query planner to materialize all function results before applying WHERE conditions, resulting in inefficient execution plans and poor performance for metadata queries that are frequently used by applications and tools.

In this change, we converts sys.columns_internal from a function to a view that directly queries PostgreSQL system catalogs using optimized joins and filtering conditions. The refactored view enables the PostgreSQL query optimizer to create better execution plans, allows for predicate pushdown, and eliminates the function scan bottleneck while maintaining full backward compatibility and providing the same column metadata with significantly improved performance for all dependent system views.

Authored-by: Rohit Bhagat rohitbgt@amazon.com
Signed-off-by: Rohit Bhagat rohitbgt@amazon.com

Issues Resolved

BABEL-6233

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

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