#609, use pipeline for delete_pattern (#617)

* #609, use pipeline for delete_pattern

* #609, add changelog description

Author: Vasyl Dizhak

README.rst

@@ -483,6 +483,15 @@ pattern syntax as the ``keys`` function and returns the number of deleted keys.
     >>> from django.core.cache import cache
     >>> cache.delete_pattern("foo_*")
 
+To achieve the best performance while deleting many keys, you should set ``DJANGO_REDIS_SCAN_ITERSIZE`` to a relatively
+high number (e.g., 100_000) by default in Django settings or pass it directly to the ``delete_pattern``.
+
+
+.. code-block:: pycon
+
+    >>> from django.core.cache import cache
+    >>> cache.delete_pattern("foo_*", itersize=100_000)
+
 Redis native commands
 ~~~~~~~~~~~~~~~~~~~~~
 

changelog.d/609.misc

@@ -0,0 +1 @@
+Speed up deleting multiple keys by a pattern with pipelines and larger itersize

django_redis/client/default.py

@@ -393,9 +393,13 @@ def delete_pattern(
 
         try:
             count = 0
+            pipeline = client.pipeline()
+
             for key in client.scan_iter(match=pattern, count=itersize):
-                client.delete(key)
+                pipeline.delete(key)
                 count += 1
+            pipeline.execute()
+
             return count
         except _main_exceptions as e:
             raise ConnectionInterrupted(connection=client) from e

tests/test_client.py

@@ -1,5 +1,5 @@
 from typing import Iterable
-from unittest.mock import Mock, patch
+from unittest.mock import Mock, call, patch
 
 import pytest
 from django.core.cache import DEFAULT_CACHE_ALIAS
@@ -104,6 +104,28 @@ def test_delete_pattern_calls_scan_iter_with_count_if_itersize_given(
             count=90210, match=make_pattern_mock.return_value
         )
 
+    @patch("test_client.DefaultClient.make_pattern")
+    @patch("test_client.DefaultClient.get_client", return_value=Mock())
+    @patch("test_client.DefaultClient.__init__", return_value=None)
+    def test_delete_pattern_calls_pipeline_delete_and_execute(
+        self, init_mock, get_client_mock, make_pattern_mock
+    ):
+        client = DefaultClient()
+        client._backend = Mock()
+        client._backend.key_prefix = ""
+        get_client_mock.return_value.scan_iter.return_value = [":1:foo", ":1:foo-a"]
+        get_client_mock.return_value.pipeline.return_value = Mock()
+        get_client_mock.return_value.pipeline.return_value.delete = Mock()
+        get_client_mock.return_value.pipeline.return_value.execute = Mock()
+
+        client.delete_pattern(pattern="foo*")
+
+        assert get_client_mock.return_value.pipeline.return_value.delete.call_count == 2
+        get_client_mock.return_value.pipeline.return_value.delete.assert_has_calls(
+            [call(":1:foo"), call(":1:foo-a")]
+        )
+        get_client_mock.return_value.pipeline.return_value.execute.assert_called_once()
+
 
 class TestShardClient:
     @patch("test_client.DefaultClient.make_pattern")