Implement support for aggregation functions implemented in Go.

sqlite3_test.go

@@ -1175,6 +1175,65 @@ func TestFunctionRegistration(t *testing.T) {
 	}
 }
 
+type sumAggregator int64
+
+func (s *sumAggregator) Step(x int64) {
+	*s += sumAggregator(x)
+}
+
+func (s *sumAggregator) Done() int64 {
+	return int64(*s)
+}
+
+func TestAggregatorRegistration(t *testing.T) {
+	customSum := func() *sumAggregator {
+		var ret sumAggregator
+		return &ret
+	}
+
+	sql.Register("sqlite3_AggregatorRegistration", &SQLiteDriver{
+		ConnectHook: func(conn *SQLiteConn) error {
+			if err := conn.RegisterAggregator("customSum", customSum, true); err != nil {
+				return err
+			}
+			return nil
+		},
+	})
+	db, err := sql.Open("sqlite3_AggregatorRegistration", ":memory:")
+	if err != nil {
+		t.Fatal("Failed to open database:", err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec("create table foo (department integer, profits integer)")
+	if err != nil {
+		t.Fatal("Failed to create table:", err)
+	}
+
+	_, err = db.Exec("insert into foo values (1, 10), (1, 20), (2, 42)")
+	if err != nil {
+		t.Fatal("Failed to insert records:", err)
+	}
+
+	tests := []struct {
+		dept, sum int64
+	}{
+		{1, 30},
+		{2, 42},
+	}
+
+	for _, test := range tests {
+		var ret int64
+		err = db.QueryRow("select customSum(profits) from foo where department = $1 group by department", test.dept).Scan(&ret)
+		if err != nil {
+			t.Fatal("Query failed:", err)
+		}
+		if ret != test.sum {
+			t.Fatalf("Custom sum returned wrong value, got %d, want %d", ret, test.sum)
+		}
+	}
+}
+
 var customFunctionOnce sync.Once
 
 func BenchmarkCustomFunctions(b *testing.B) {