Problem

When parsing PostgreSQL function defaults, pg_proc.proargdefaults converted with pg_get_expr() returns a single comma-separated string containing all default values, rather than an array.

This creates several challenges:

1. The default values need to be split from the comma-separated string
2. These values must then be aligned to the rightmost input arguments (since only trailing arguments can have defaults in PostgreSQL)
3. Edge cases exist where commas might legitimately appear within default values themselves, making naive string splitting unreliable

Solution

Instead of parsing and realigning the comma-separated string, this PR uses PostgreSQL's pg_get_function_arg_default() function to retrieve the default value for each argument individually. This function:

• Takes an argument position and returns the default for that specific argument
• Returns the properly formatted default expression
• Avoids any ambiguity around parsing comma-separated values
• Eliminates the need for complex right-alignment logic