fix: table function

[tianzhou]

Fix #101

[Copilot]

Pull Request Overview

This PR fixes the handling of PostgreSQL table functions that use the newer RETURN clause syntax (introduced in PostgreSQL 14) instead of the traditional AS $$ ... $$ block syntax. The fix addresses issue #103 by updating SQL queries to use pg_get_function_sqlbody() and modifying code generation logic to detect and properly format functions with RETURN clauses.

• Updates SQL queries to use pg_get_function_sqlbody() with fallback to prosrc for extracting function definitions
• Adds logic to detect and handle RETURN clause syntax in function/procedure SQL generation
• Includes test case for table function using RETURN clause with SETOF timestamptz

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
ir/queries/queries.sql	Added COALESCE with pg_get_function_sqlbody() to properly extract function bodies that use RETURN clause syntax
ir/queries/queries.sql.go	Generated code reflecting SQL query changes for function/procedure retrieval
internal/diff/function.go	Added conditional logic to detect RETURN clause syntax and format it without dollar quoting
internal/diff/procedure.go	Added same RETURN clause detection logic for procedures
testdata/diff/create_function/add_function/.	Test data files demonstrating the fix with a new table function using RETURN clause

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