mongodb: wrap `Collection::aggregate` function

[nit.git] / lib / mongodb / mongodb.nit

diff --git a/lib/mongodb/mongodb.nit b/lib/mongodb/mongodb.nit
index ab4d387..cd203e4 100644 (file)
--- a/lib/mongodb/mongodb.nit
+++ b/lib/mongodb/mongodb.nit
@@ -580,6 +580,41 @@ class MongoCollection
                return res
        end
 
+       # Applies an aggregation `pipeline` over the collection.
+       #
+       # ~~~
+       # var client = new MongoClient("mongodb://localhost:27017/")
+       # var col = client.database("test").collection("test_aggregate")
+       #
+       # col.drop
+       #
+       # col.insert("""{ "cust_id": "A123", "amount": 500, "status": "A"}""".parse_json.as(JsonObject))
+       # col.insert("""{ "cust_id": "A123", "amount": 250, "status": "A"}""".parse_json.as(JsonObject))
+       # col.insert("""{ "cust_id": "B212", "amount": 200, "status": "A"}""".parse_json.as(JsonObject))
+       # col.insert("""{ "cust_id": "A123", "amount": 300, "status": "D"}""".parse_json.as(JsonObject))
+       #
+       # var res = col.aggregate("""[
+       #       { "$match": { "status": "A" } },
+       #       { "$group": { "_id": "$cust_id", "total": { "$sum": "$amount" } } }
+       # ]""".parse_json.as(JsonArray))
+       #
+       # assert res[0].to_json == """{"_id":"B212","total":200}"""
+       # assert res[1].to_json == """{"_id":"A123","total":750}"""
+       # ~~~
+       fun aggregate(pipeline: JsonArray): Array[JsonObject] do
+               var q = new JsonObject
+               q["pipeline"] = pipeline
+               var res = new Array[JsonObject]
+               var c = native.aggregate(q.to_bson.native)
+               if c == null then return res
+               var cursor = new MongoCursor(c)
+               while cursor.is_ok do
+                       res.add cursor.item
+                       cursor.next
+               end
+               return res
+       end
+
        # Retrieves statistics about the collection.
        #
        # Returns `null` if an error occured. See `Sys::last_mongoc_error`.