aggregation feature added

common_helper_mongo/__init__.py

 from .gridfs import overwrite_file
+from .aggregate import get_objects_and_count_of_occurrence
 
 __all__ = [
-           'overwrite_file'
+           'overwrite_file',
+           'get_objects_and_count_of_occurrence'
         ]

common_helper_mongo/aggregate.py

+import logging
+from bson.son import SON
+
+
+def get_objects_and_count_of_occurrence(collection, object_path, unwind=False, match=None):
+    pipeline = []
+    if match is not None:
+        pipeline.append({"$match": match})
+    pipeline.extend([
+        {"$group": {"_id": object_path, "count": {"$sum": 1}}},
+        {"$sort": SON([("count", -1), ("_id", -1)])}
+        ])
+    if unwind:
+        old_pipe = pipeline
+        pipeline = [{"$unwind": object_path}]
+        pipeline.extend(old_pipe)
+    result = list(collection.aggregate(pipeline))
+    logging.debug(result)
+    return result

tests/base_class_database_test.py

@@ -7,10 +7,20 @@ class MongoDbTest(unittest.TestCase):
     def setUp(self):
         self.mongo_client = MongoClient()
         self.db = self.mongo_client["common_code_test"]
+        self.test_collection = self.db.test_data
 
     def tearDown(self):
         self.mongo_client.drop_database(self.db)
         self.mongo_client.close()
 
+    def add_simple_test_data(self):
+        for i in range(10):
+            self.test_collection.insert_one({"test_int": i, "test_txt": "item {}".format(i)})
+        self.test_collection.insert_one({"test_txt": "item 1"})
+
+    def add_list_test_data(self):
+        self.test_collection.insert_one({"test_list": ["a", "b", "c"]})
+        self.test_collection.insert_one({"test_list": ["c", "d"]})
+
 if __name__ == "__main__":
     unittest.main()

tests/test_aggregate.py

+from common_helper_mongo.aggregate import get_objects_and_count_of_occurrence
+import unittest
+from tests.base_class_database_test import MongoDbTest
+
+
+class TestAggregate(MongoDbTest):
+
+    def test_get_objects_and_count_of_occurence(self):
+        self.add_simple_test_data()
+        result = get_objects_and_count_of_occurrence(self.test_collection, "$test_txt", unwind=False, match=None)
+        self.assertEqual(len(result), 10, "number of results not correct")
+        self.assertEqual(result[0]['_id'], "item 1", "should be the fist element because it has two ocurrences")
+        self.assertEqual(result[0]['count'], 2)
+
+    def test_get_objects_and_count_unwind(self):
+        self.add_list_test_data()
+        result = get_objects_and_count_of_occurrence(self.test_collection, "$test_list", unwind=True, match=None)
+        self.assertEqual(len(result), 4, "number of results not correct")
+        self.assertEqual(result[0]['_id'], "c", "should be the first element because it has two ocurrences")
+        self.assertEqual(result[0]['count'], 2)
+
+
+if __name__ == "__main__":
+    unittest.main()