How to diagnose and fix the 55P04 unsafe_new_enum_value_usage error code in Postgres.

The 55P04 error code in PostgreSQL, which stands for unsafe_new_enum_value_usage, is not a standard PostgreSQL error and does not appear in the official list of PostgreSQL error codes. It’s possible that this error code might be related to a specific extension or a customized version of PostgreSQL.

However, generally speaking, issues related to enum types in PostgreSQL can occur when you try to modify an enum type in a way that could potentially cause inconsistencies or when an application relies on the existing enum values and their order.

Here’s how you might diagnose and address issues with enum types in PostgreSQL:

  1. Adding a New Enum Value
    When adding a new value to an existing enum type, you must ensure that it does not disrupt the operation of any applications or queries that depend on the enum type. Example:
   ALTER TYPE my_enum_type ADD VALUE 'new_value';

Before adding a new value, check that no application logic or database constraints will be adversely affected by the change. If necessary, update application code or database logic to accommodate the new enum value.

  1. Removing or Modifying an Enum Value
    PostgreSQL does not provide a direct way to remove or modify existing enum values because it could lead to data inconsistency. Example:
    There is no direct SQL command to remove an enum value, but attempting to do so would cause issues. Fix:
    To remove or modify an enum value, you would typically need to create a new enum type with the desired values, update all columns using the old enum type to the new type, and then drop the old enum type. Here’s a way to replace an old enum type with a modified one:
   -- Create a new enum type
   CREATE TYPE new_enum_type AS ENUM ('existing_value1', 'new_value', 'existing_value2');

   -- Update the column to use the new enum type
   ALTER TABLE my_table ALTER COLUMN my_enum_column TYPE new_enum_type USING my_enum_column::text::new_enum_type;

   -- Drop the old enum type
   DROP TYPE my_enum_type;

   -- Optionally, rename the new enum type to the old name
   ALTER TYPE new_enum_type RENAME TO my_enum_type;
  1. Using Enum Values in Unsafe Ways
    If an application uses enum values in a way that assumes a particular order or depends on the values in a way that isn’t safe for changes, this could cause issues when the enum type is altered. Example:
    Applications that use enum values directly without accounting for potential changes might experience issues if the enum type is modified. Fix:
    Ensure that your application does not rely on the order or the specific set of enum values. Instead, use checks or mappings within the application to handle enum values safely and flexibly.

To diagnose issues with enum types:

  • Review the application code and database schema for any dependencies on the enum type.
  • Check if the error occurs after a recent change to an enum type.
  • Use the pg_enum system catalog to inspect the values of the enum type.

When fixing issues related to enum types, always proceed with caution to avoid data inconsistencies and application errors. Make sure to back up your data before making changes to the enum type.

For more information on working with enum types in PostgreSQL, you can refer to the official PostgreSQL documentation on enumerated types.

If you are dealing with a specific extension or customized PostgreSQL that uses the 55P04 error code, you may need to consult the documentation for that extension or the source code of the customized PostgreSQL instance for more details on how to handle this error.

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