add llen to dbal

src/database/mongo/list.js

@@ -100,4 +100,13 @@ module.exports = function (db, module) {
 			callback(null, data.array);
 		});
 	};
+
+	module.listLength = function (key, callback) {
+		db.collection('objects').aggregate([
+			{ $match: { _key: key } },
+			{ $project: { count: { $size: "$array" } } },
+		], function (err, result) {
+			callback(err, Array.isArray(result) && result.length && result[0].count);
+		});
+	};
 };

src/database/redis/list.js

@@ -56,4 +56,8 @@ module.exports = function (redisClient, module) {
 		}
 		redisClient.lrange(key, start, stop, callback);
 	};
+
+	module.listLength = function (key, callback) {
+		redisClient.llen(key, callback);
+	};
 };

test/database/list.js

@@ -200,4 +200,19 @@ describe('List methods', function () {
 			});
 		});
 	});
+
+
+	it('should get the length of a list', function (done) {
+		db.listAppend('getLengthList', 1, function (err) {
+			assert.ifError(err);
+			db.listAppend('getLengthList', 2, function (err) {
+				assert.ifError(err);
+				db.listLength('getLengthList', function (err, length) {
+					assert.ifError(err);
+					assert.equal(length, 2);
+					done();
+				});
+			});
+		});
+	});
 });