Make sure sampled data in buffer is different from each other

ding/worker/buffer/deque_buffer.py

 from typing import Any, Iterable, List, Optional, Union
-from collections import deque
+from collections import defaultdict, deque
 from ding.worker.buffer import Buffer, apply_middleware, BufferedData
+from ding.worker.buffer.utils import fastcopy
 import itertools
 import random
 import uuid
@@ -65,6 +66,8 @@ class DequeBuffer(Buffer):
             else:
                 raise ValueError("There are less than {} data in buffer({})".format(size, self.count()))
 
+        sampled_data = self._independence(sampled_data)
+
         return sampled_data
 
     @apply_middleware("update")
@@ -93,6 +96,19 @@ class DequeBuffer(Buffer):
     def clear(self) -> None:
         self.storage.clear()
 
+    def _independence(self, buffered_samples: List[BufferedData]) -> List[BufferedData]:
+        """
+        Overview:
+            Make sure that each record is different from each other, but remember that this function
+            is different from clone_object. You may change the data in the buffer by modifying a record.
+        """
+        occurred = defaultdict(int)
+        for i, buffered in enumerate(buffered_samples):
+            occurred[buffered.index] += 1
+            if occurred[buffered.index] > 1:
+                buffered_samples[i] = fastcopy.copy(buffered)
+        return buffered_samples
+
     def __iter__(self) -> deque:
         return iter(self.storage)
 

ding/worker/buffer/tests/test_buffer.py

@@ -165,3 +165,25 @@ def test_ignore_insufficient():
         buffer.sample(3, ignore_insufficient=False)
     data = buffer.sample(3, ignore_insufficient=True)
     assert len(data) == 0
+
+
+@pytest.mark.unittest
+def test_independence():
+    # By replace
+    buffer = DequeBuffer(size=1)
+    data = {"key": "origin"}
+    buffer.push(data)
+    sampled_data = buffer.sample(2, replace=True)
+    assert len(sampled_data) == 2
+    sampled_data[0].data["key"] = "new"
+    assert sampled_data[1].data["key"] == "origin"
+
+    # By indices
+    buffer = DequeBuffer(size=1)
+    data = {"key": "origin"}
+    buffered = buffer.push(data)
+    indices = [buffered.index, buffered.index]
+    sampled_data = buffer.sample(indices=indices)
+    assert len(sampled_data) == 2
+    sampled_data[0].data["key"] = "new"
+    assert sampled_data[1].data["key"] == "origin"