psycopg2 --> psycopg3 breaking change: python type for bytea data changed.

[powderflask]

in psycopg2 bytea data was returned as a memoryview
psycopg3 returns a bytes object.

Its not clear why this should cause a breaking change, but in my use case, this django code fragment works with psycopg2.
The model has a BinaryField named data. Here I fetch an instance and return it as a FileResponse:

    obj = self.get_object()
    response = http.FileResponse(obj.data, as_attachment=True, filename=self.object.name)

A solution that works with either adapter - just wrap the data buffer in an iterable:

    obj = self.get_object()
    response = http.FileResponse((obj.data,), as_attachment=True, filename=self.object.name)

Not clear to me the nature of the breaking change, just that this code has been in production for ~5 years and broke when I upgraded.
I suspect this is something about the way django handles the data buffer (comments in StreamingHttpResponse do say streaming_content should be an iterable of bytestrings.`) , combined with something subtle about the difference in how it is being produced by the 2 adapters, but I don't have a coherent story yet.
Hoping someone who understands this could explain in a way that would allow me to document this issue in either Django or psycopg docs (or, more likely, where I've gone wrong ;-). thanks.

[dvarrazzo]

Not clear to me the nature of the breaking change, just that this code has been in production for ~5 years and broke when I upgraded.

psycopg 3 has breaking changes in the interface and data adaptation rules. This is documented and it is not expected that your code working with psycopg2 works with psycopg 3.