Fix handling of prepared collections

[hampuskraft]

I experienced some issues regarding type marshaling of maps, such as map<int, bigint>:

scyllapy.exceptions.ScyllaPyDBError: Database returned an error: The query is syntactically correct but invalid, Error message: Exception while binding column permissions: marshaling error: Validation failed for type org.apache.cassandra.db.marshal.LongType: got 4 bytes

After digging through the code, I identified the issue: If column_type is a Map—such as Map(Int, BigInt) in this case—the PyDict case of py_to_value would pass along ColumnType::Map to as the column_type to the recursive call, and since default match in the PyInt case was int32, it would incorrectly pass an int32 to a bigint field.

To make issues like these simpler to debug in the future, I also refactored the PyInt and PyFloat cases not to choose an implicit default but instead return a BindingError if an unsupported type were to be bound.

[hampuskraft]

I also noticed that sets weren't working as expected since it, too, passed the wrong column type to serialize its children. The same goes for tuples. However, tuples may also contain mixed data types. The two test cases I added for tuples are failing. Let me know if you have any ideas why that might be! Thanks.

scylla = <builtins.Scylla object at 0x1020c1730>, type_name = 'TUPLE<INT, INT>', test_val = (1, 2), cast_func = <class 'tuple'>

E       scyllapy.exceptions.ScyllaPyDBError: Database returned an error: The query is syntactically correct but invalid, Error message: Exception while binding column coll: marshaling error: Validation failed for type org.apache.cassandra.db.marshal.Int32Type: got 2 bytes

(And similarly for the TUPLE<INT, TEXT, FLOAT> test case, although there it got 3 bytes.)

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[s3rius]

Hello! Thanks for your cotribution. Have you tried using BigInt instead of python's integer? There're extra types which you can use: https://github.com/Intreecom/scyllapy#extra-types

The column_type parameter only set for prepared queries, it won't work for ordinary queries.

Agree about floats.

[hampuskraft]

Yeah.

I'm only using prepared queries in my app to avoid having to transform my query parameters to use ScyllaPy's extra types, and I noticed that a few things did not work since it passed the container type rather than the type of the contained value when converting them—I believe this would be on the right path? Automatic type conversion would indeed only be possible with prepared queries, so I'm only testing those.

The logic for handling tuples would need to be fixed to pass the prepared collections test since ScyllaDB currently complains about getting 2-3 bytes instead of the expected 4 bytes for an Int32Type when serializing tuple<int, int>, for instance. Nevertheless, I'm currently using my fork in my application without any issues since I'm not yet using tuples, but I do use sets & maps and would prefer not to cast the types manually.

I unfortunately don't have much time to work on this at the moment—I would appreciate any ideas you might have to finalize this and perhaps make it a bit cleaner.

Thanks!

[s3rius]

Will see what I can do to fix that moment.