The database state created by this fixture is equivalent to the following operations using arctic 1.40
    or previous:

        arctic.initialize_library('arctic_test.TEST', m.VERSION_STORE, segment='month')
        library = arctic.get_library('arctic_test.TEST')
        df = pd.DataFrame([[1,2], [3,4]], index=['x','y'], columns=[['a','w'], ['a','v']])
        library.write('pandas', df)

    different from newer versions, the last write creates a uncompressed chunk.

def multicolumn_store_with_uncompressed_write(mongo_server):
    """
    The database state created by this fixture is equivalent to the following operations using arctic 1.40
    or previous:

        arctic.initialize_library('arctic_test.TEST', m.VERSION_STORE, segment='month')
        library = arctic.get_library('arctic_test.TEST')
        df = pd.DataFrame([[1,2], [3,4]], index=['x','y'], columns=[['a','w'], ['a','v']])
        library.write('pandas', df)

    different from newer versions, the last write creates a uncompressed chunk.
    """
    mongo_server.api.drop_database('arctic_test')

    library_name = 'arctic_test.TEST'
    arctic = m.Arctic(mongo_host=mongo_server.api)
    arctic.initialize_library(library_name, m.VERSION_STORE, segment='month')

    db = mongo_server.api.arctic_test
    db.TEST.insert_many([
        {
            'parent': [bson.ObjectId('5ad0dc065c911d1188b512d8')],
            'data': bson.Binary(b'\x11\x00\x00\x002x\x01\x00\x01\x00\x80\x02\x00\x00\x00\x00\x00\x00\x00', 0),
            'symbol': 'pandas',
            'sha': bson.Binary(b'\xaa\\`\x0e\xc2D-\xc1_\xf7\xfd\x12\xfa\xd2\x17\x05`\x00\x98\xe2', 0),
            'compressed': True,
            '_id': bson.ObjectId('5ad0dc067934ecad404070be'),
            'segment': 0
        },
        {
            'parent': [bson.ObjectId('5ad0dc065c911d1188b512d8')],
            'data': bson.Binary(b'y\x03\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00', 0),
            'symbol': 'pandas',
            'sha': bson.Binary(b'\xfe=WQ\xb5\xfdL\xb7\xcavd\x85o\x04]\x04\xdb\xa8]3', 0),
            'compressed': False,
            '_id': bson.ObjectId('5ad0dc077934ecad404070bf'),
            'segment': 1
        }
    ])
    db.TEST.ARCTIC.update_one({"_id": "ARCTIC_META"}, {"$set": {"_id": "ARCTIC_META", "TYPE": "VersionStore", "QUOTA": 10737418240}})
    db.TEST.version_nums.insert_one({'symbol': 'pandas', '_id': bson.ObjectId('5ad0dc067934ecad404070bd'), 'version': 2})
    db.TEST.versions.insert_many([
        {
            'append_count': 0,
            'dtype_metadata': {
                'index': ['index'],
                'columns': ["('a', 'a')", "('w', 'v')"]
            },
            'segment_count': 1,
            'dtype': '[(\'index\', \'S1\'), ("(\'a\', \'a\')", \'<i8\'), ("(\'w\', \'v\')", \'<i8\')]',
            'symbol': 'pandas',
            'up_to': 1,
            'metadata': None,
            'sha': bson.Binary(b'\xf2\x15h\x9d\x925\x95\xa5\x0e\x95J\xc4x\xfc\xfc\xd5\x80\xe0\x1d\xef', 0),
            'shape': [-1],
            'version': 1,
            'base_sha': bson.Binary(b'\xf2\x15h\x9d\x925\x95\xa5\x0e\x95J\xc4x\xfc\xfc\xd5\x80\xe0\x1d\xef', 0),
            '_id': bson.ObjectId('5ad0dc065c911d1188b512d8'),
            'type': 'pandasdf',
            'append_size': 0
        },
        {
            'append_count': 1,
            'dtype_metadata': {
                'index': ['index'],
                'columns': ["('a', 'a')", "('w', 'v')"]
            },
            'segment_count': 2,
            'sha': bson.Binary(b'1\x83[ZO\xec\x080D\x80f\xe4@\xe4\xd3\x94yG\xe2\x08', 0),
            'dtype': '[(\'index\', \'S1\'), ("(\'a\', \'a\')", \'<i8\'), ("(\'w\', \'v\')", \'<i8\')]',
            'symbol': 'pandas',
            'up_to': 2,
            'metadata': None,
            'base_version_id': bson.ObjectId('5ad0dc065c911d1188b512d8'),
            'shape': [-1],
            'version': 2,
            'base_sha': bson.Binary(b'\xf2\x15h\x9d\x925\x95\xa5\x0e\x95J\xc4x\xfc\xfc\xd5\x80\xe0\x1d\xef', 0),
            '_id': bson.ObjectId('5ad0dc075c911d1188b512d9'),
            'type': 'pandasdf',
            'append_size': 17
        }
    ])

    return {'symbol': 'pandas', 'store': arctic.get_library('arctic_test.TEST')}