To unwrap and prove the recovery of PL/pgSQL source code in PostgreSQL, you need to follow a process that involves accessing the stored code from the database system catalogs and then validating its integrity. Here’s a step-by-step approach to achieve this:

Unwrapping PL/pgSQL Source Code

PL/pgSQL functions and procedures in PostgreSQL are stored in the pg_proc system catalog. The actual source code of these functions is stored in the prosrc column. To unwrap or recover the source code, you can query this catalog.

1. Access the Function's Source Code:

   • Use the following SQL query to retrieve the source code of a specific function:

     SELECT prosrc FROM pg_proc WHERE proname = 'your_function_name';
     

   • Replace your_function_name with the name of the function whose source code you want to retrieve.

2. Display Function Definition:

   • PostgreSQL also provides the pg_get_functiondef function, which returns the complete SQL command to recreate a function. This is useful for getting the entire function definition, including parameters and return type.

     SELECT pg_get_functiondef('your_function_oid_or_name');
     

   • Here, replace your_function_oid_or_name with the OID or name of the function.

Proving the Code is Recovered

To prove that the code is accurately recovered, you can compare the unwrapped code with the original source code (if available) or validate its functionality by executing it.

1. Code Comparison:
   • If you have the original source code, compare it with the unwrapped code for any discrepancies.
   • You can use text comparison tools or simply check manually if the code base is not extensive.
2. Functionality Test:
   • Run the function with known inputs and compare the outputs with expected results.
   • If the function interacts with the database (e.g., modifies data), check the state of the relevant tables before and after the function execution.
3. Checking Comments and Formatting:
   • Be aware that comments and certain formatting might not be preserved exactly as in the original source code. The core logic of the function, however, should be identical.
4. Version Control Systems:
   • If the original function was version-controlled, you can pull the same version from your VCS and compare it with the recovered code.
5. Re-creation Test:
   • Use the result of pg_get_functiondef to create the function in a test database and ensure it compiles and runs as expected.

Considerations

• Security and Permissions: Ensure that you have the necessary permissions to access the system catalogs and retrieve the function’s source code.
• Database Version: Be aware of any differences in PostgreSQL versions that might affect function behavior or SQL syntax.

Conclusion

Unwrapping PL/pgSQL source code in PostgreSQL is straightforward using system catalog queries. Validating the recovered code involves comparing it with the original (if available), testing its functionality, and ensuring it behaves as expected. This process is essential for scenarios like database migration, audit, or simply code recovery when the original source is lost.