cluster scan returns a dict as cursor

[amirreza8002]

hi
so the cluster client runs this function on the return value of scan https://github.com/valkey-io/valkey-py/blob/main/valkey/cluster.py#L56

which would look something like this in a test example:

cursor={'127.0.0.1:7000': 0, '127.0.0.1:7001': 0, '127.0.0.1:7002': 0}
result=['foo2', 'foo3', 'foo1']

i understand that this is intended behaviour, but am wondering if this is necessary
valkey itself returns a single number

but if it's here to stay, we should probably document it

[amirreza8002]

hmm
there seems to be more to this than i thought
i'll do more digging

[mkmkme]

Any update on digging?

[amirreza8002]

ah sorry I'd totally forgotten about this
I'll look tonight

[amirreza8002]

so the process seems to be like this:

scan calls execute_command, then it does self._process_result(...)
which then checks RESULT_CALLBACKS for a call back function, which would be parse_scan_result in our case
which does what i opened here (returning a dict of {server: cursor} as a cursor)

in it's early versions it would just return a hardcoded 0, it seems

it was then changed in this pr

the problem is that when using valkey-cli, the behaviour is different
from what i can tell, when using valkey-cli to connect to cluster, using scan only scans one node, and it just returns one cursor and a list of keys
but it's not the case here

so i think both valkey-py and valkey itself should document this behaviour in detail.

[mkmkme]

Thanks for the detailed investigation! I'll have a look. Probably we should document this behaviour properly. Changing it now would be a breaking change. If we get any complains about this behaviour, we might think about changing it.