Cassandra / ScyllaDB date fields can't serialize into JSON

[susodapop]

Issue Summary

The CassandraJSONEncoder doesn't support encoding Python Date() objects:

redash/redash/query_runner/cass.py

Lines 32 to 36 in d036df0

	class CassandraJSONEncoder(JSONEncoder):
	def default(self, o):
	if isinstance(o, sortedset):
	return list(o)
	return super(CassandraJSONEncoder, self).default(o)

Steps to Reproduce

1. Run SELECT date_field FROM table against Cassandra or ScyllaDB
2. Observe the error: "Error running query: Object of type Date is not JSON serializable"

Technical details:

• Redash Version: v9 Alpha
• Browser/OS: Firefox / Safari / Chrome
• How did you install Redash: SaaS

[susodapop]

What's interesting is that Redash's JSONEncoder does support dates (see line 90).

redash/redash/utils/__init__.py

Lines 71 to 104 in d036df0

	class JSONEncoder(simplejson.JSONEncoder):
	"""Adapter for `simplejson.dumps`."""
	def default(self, o):
	# Some SQLAlchemy collections are lazy.
	if isinstance(o, Query):
	result = list(o)
	elif isinstance(o, decimal.Decimal):
	result = float(o)
	elif isinstance(o, (datetime.timedelta, uuid.UUID)):
	result = str(o)
	# See "Date Time String Format" in the ECMA-262 specification.
	elif isinstance(o, datetime.datetime):
	result = o.isoformat()
	if o.microsecond:
	result = result[:23] + result[26:]
	if result.endswith("+00:00"):
	result = result[:-6] + "Z"
	elif isinstance(o, datetime.date):
	result = o.isoformat()
	elif isinstance(o, datetime.time):
	if o.utcoffset() is not None:
	raise ValueError("JSON can't represent timezone-aware times.")
	result = o.isoformat()
	if o.microsecond:
	result = result[:12]
	elif isinstance(o, memoryview):
	result = binascii.hexlify(o).decode()
	elif isinstance(o, bytes):
	result = binascii.hexlify(o).decode()
	else:
	result = super(JSONEncoder, self).default(o)
	return result

[susodapop]

Just a note for other searchers: you can work around this by casting to TIMESTAMP like so:

SELECT CAST(datefield AS TIMESTAMP) "new_date_alias" FROM table

[tim5go]

@susodapop
https://github.com/datastax/python-driver/blob/master/cassandra/util.py

From the above code snippet, I believe the cassandra python driver casts a date_field into a cassandra custom Date object cassandra.util.Date (rather than datetime.date).

That's why the CassandraJSONEncoder is throwing error when it encounters date_field.