[GitHub] [flink] shuiqiangchen commented on a change in pull request #13097: [FLINK-18864][python] Support key_by() operation for Python DataStrea…

[GitBox <gi...@apache.org>]

shuiqiangchen commented on a change in pull request #13097:
URL: https://github.com/apache/flink/pull/13097#discussion_r467721304



##########
File path: flink-python/pyflink/datastream/tests/test_data_stream.py
##########
@@ -140,15 +135,68 @@ def flat_map(value):
 
         flat_mapped_stream = ds.flat_map(flat_map, type_info=Types.ROW([Types.STRING(),
                                                                         Types.INT()]))
-        collect_util = DataStreamCollectUtil()
-        collect_util.collect(flat_mapped_stream)
+        self.collect_util.collect(flat_mapped_stream)
         self.env.execute('flat_map_test')
-        results = collect_util.results()
+        results = self.collect_util.results()
         expected = ['a,0', 'bdc,2', 'deeefg,4']
         results.sort()
         expected.sort()
         self.assertEqual(expected, results)
 
+    def test_key_by(self):
+        element_collection = [('a', 0), ('b', 0), ('c', 1), ('d', 1), ('e', 2)]
+        self.env.set_parallelism(1)
+        ds = self.env.from_collection(element_collection,
+                                      type_info=Types.ROW([Types.STRING(), Types.INT()]))
+
+        class AssertKeyMapFunction(MapFunction):
+            def __init__(self):
+                self.pre = None
+
+            def map(self, value):
+                if value[0] == 'b':
+                    assert self.pre == 'a'
+                if value[0] == 'd':
+                    assert self.pre == 'c'
+                self.pre = value[0]
+                return value
+
+        mapped_stream = ds.key_by(MyKeySelector()).map(AssertKeyMapFunction())
+        self.collect_util.collect(mapped_stream)
+        self.env.execute('key_by_test')
+        results = self.collect_util.results()
+        expected = ["<Row('a', 0)>", "<Row('b', 0)>", "<Row('c', 1)>", "<Row('d', 1)>",
+                    "<Row('e', 2)>"]
+        results.sort()
+        expected.sort()
+        self.assertEqual(expected, results)
+
+    def test_key_by_map(self):

Review comment:
       They are almost the same, but the second test is to make sure we have not changed the original DataStream after key_by() operation with two way map operation.




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