Ah, this is a straightforward issue. The error you're seeing occurs because while you've correctly configured the PostgreSQL connection, the Prefect server container doesn't have the required PostgreSQL driver installed. To fix this, you need to add psycopg2 to your Prefect server deployment. There are two ways to handle this: 1. Modify the Helm values.yaml (Recommended):

yaml
server:
  extraPipPackages:
    - "psycopg2-binary"

2. Build a custom image (Alternative approach): Create a Dockerfile:

dockerfile
FROM prefecthq/prefect:3-python3.11
RUN pip install psycopg2-binary

The first approach using

extraPipPackages

is simpler and doesn't require maintaining a custom image. After making this change, redeploy your Helm chart:

bash
helm upgrade prefect prefecthq/prefect -f values.yaml

A few additional notes: - Use

psycopg2-binary

instead of

psycopg2

to avoid requiring additional system-level dependencies - Make sure your PostgreSQL instance has the

pg_trgm

extension enabled - Verify your connection string is properly formatted as:

<postgresql://user:password@host:port/dbname>

If you continue to experience issues after implementing these changes, please check the server logs for any additional error messages.

You're right - it should be installed by default when using PostgreSQL. This has been a known issue in the past and while it was fixed for Prefect 2.x, it seems to have resurfaced in the 3.x images. I'll make this clearer: The

psycopg2

dependency should indeed be included by default when PostgreSQL is configured, as it's a core requirement for PostgreSQL functionality. The fact that it isn't is a bug. For now, you'll need to use the workaround I mentioned earlier (adding

psycopg2-binary

via

extraPipPackages

), but I'd encourage you to open an issue on the Prefect GitHub repository to track this. This would help ensure it gets properly fixed in future releases. The reason

psycopg2-binary

is recommended over

psycopg2

is that it includes all necessary binary dependencies, avoiding the need for additional system-level PostgreSQL development packages that would be required to build

psycopg2

from source. Would you like me to provide the exact issue template to use when reporting this bug?

Ah yes, you're absolutely right - I apologize for not catching this distinction! This is a perfect example of why precision matters in connection strings. In Prefect 3.x, the server uses SQLAlchemy's async functionality, which requires the

asyncpg

driver rather than

psycopg2

. The connection string format needs to explicitly specify this:

<postgresql+asyncpg://user:password@host:port/dbname>

This is actually a much better solution because: 1.

asyncpg

is already included in the Prefect image by default 2. It's significantly faster than

psycopg2

due to its native async implementation 3. It aligns better with Prefect's async architecture Thank you for the correction. This is a common point of confusion that comes up, as the standard PostgreSQL connection string format (

postgresql://

) will try to use

psycopg2

by default, while

postgresql+asyncpg://

explicitly tells SQLAlchemy to use the async driver.