@Marvin im suddenly getting this issue :

ValueError: Unable to create hash - objects could not be serialized.
  JSON error: Unable to serialize unknown type: <class 'postgres_client.PostgresClient'>
  Pickle error: cannot pickle 'psycopg2.extensions.connection' object

This often occurs when task inputs contain objects that cannot be cached like locks, file handles, or other system resources.

To resolve this, you can:
  1. Exclude these arguments by defining a custom `cache_key_fn`
  2. Disable caching by passing `cache_policy=NO_CACHE`

how come?

Your issue arises because the Prefect task inputs include objects that cannot be serialized, such as database connections or other non-serializable types. This is a common problem when dealing with objects that have complex internal states or are tied to system resources. Here's a concise breakdown of how to address this problem: 1. Custom `cache_key_fn`: You can define a custom function to exclude non-serializable objects from being cached. This function will compute a cache key using only the serializable parts of the task inputs. You can find more about this in the Prefect documentation on task caching. 2. Disable Caching: If caching is not necessary for your task, you can disable it by setting

cache_policy=NO_CACHE

. This will prevent Prefect from attempting to serialize and cache the task inputs. 3. Result Persistence: Ensure that result persistence is off if you don't need it, as caching requires result persistence, which is off by default. For further details, you might want to explore the Prefect GitHub issues related to serialization and caching for additional context and solutions.