From c22940be544d06c2c4fbfa6f635d215bc6a11ada Mon Sep 17 00:00:00 2001
From: akhokhan <akhokhani@goagilant.com>
Date: Mon, 26 Oct 2026 16:46:03 -0500
Subject: [PATCH] Release completed keyed partition state

---
 streamz/core.py            |  5 +--
 streamz/tests/test_core.py | 63 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/streamz/core.py b/streamz/core.py
index 6d49d5a8..63ad7329 100644
--- a/streamz/core.py
+++ b/streamz/core.py
@@ -1138,8 +1138,9 @@ def _get_key(self, x):
 
     @gen.coroutine
     def _flush(self, key):
-        result, self._buffer[key] = self._buffer[key], []
-        metadata_result, self._metadata_buffer[key] = self._metadata_buffer[key], []
+        result = self._buffer.pop(key)
+        metadata_result = self._metadata_buffer.pop(key)
+        self._callbacks.pop(key, None)
         yield self._emit(tuple(result), list(metadata_result))
         self._release_refs(metadata_result)
 
diff --git a/streamz/tests/test_core.py b/streamz/tests/test_core.py
index 67261255..45becd9b 100644
--- a/streamz/tests/test_core.py
+++ b/streamz/tests/test_core.py
@@ -1880,3 +1880,66 @@ def run(self):
 
     wait_for(lambda: L == [0], 0.01)
     assert len(source_list) > 0
+
+
+@pytest.mark.parametrize("n", [1, 2])
+@pytest.mark.parametrize("timeout", [None, 60])
+@pytest.mark.asyncio
+async def test_partition_releases_completed_keys(n, timeout):
+    source = Stream(asynchronous=True)
+    node = source.partition(n, key=0, timeout=timeout)
+    output = node.sink_to_list()
+    for key in range(8):
+        for value in range(n):
+            await source.emit((key, value))
+    assert output == [tuple((key, value) for value in range(n))
+                      for key in range(8)]
+    assert not node._buffer
+    assert not node._metadata_buffer
+    assert not node._callbacks
+
+
+@pytest.mark.asyncio
+async def test_partition_releases_timed_out_keys():
+    source = Stream(asynchronous=True)
+    node = source.partition(2, key=0, timeout=0.001)
+    output = node.sink_to_list()
+    for key in range(8):
+        await source.emit((key, 0))
+    await await_for(lambda: len(output) == 8, timeout=2)
+    assert sorted(output) == [((key, 0),) for key in range(8)]
+    assert not node._buffer
+    assert not node._metadata_buffer
+    assert not node._callbacks
+
+
+@pytest.mark.asyncio
+async def test_partition_same_key_while_emitting():
+    source = Stream(asynchronous=True)
+    node = source.partition(2, key=0, timeout=60)
+    entered = asyncio.Event()
+    release = asyncio.Event()
+    output = []
+
+    async def sink(batch):
+        output.append(batch)
+        if len(output) == 1:
+            entered.set()
+            await release.wait()
+
+    node.sink(sink)
+    await source.emit((1, 0))
+    pending = source.emit((1, 1))
+    try:
+        await asyncio.wait_for(entered.wait(), timeout=2)
+        await source.emit((1, 2))
+        assert node._buffer[1] == [(1, 2)]
+        assert 1 in node._callbacks
+    finally:
+        release.set()
+        await asyncio.wait_for(pending, timeout=2)
+    await source.emit((1, 3))
+    assert output == [((1, 0), (1, 1)), ((1, 2), (1, 3))]
+    assert not node._buffer
+    assert not node._metadata_buffer
+    assert not node._callbacks