Improve database check performance: replace introspection.table_names…

…() by a simple cursor query (mwarkentin#171) * Improve database check performance: replace introspection.table_names() by just a SELECT 1 * add test * fix tests * change patch path * fix local tests * fix pre-commit * undo changes * update history Co-authored-by: Michael Warkentin <mwarkentin@hey.com>
cayla · Jan 10, 2022 · b4c3c30 · b4c3c30
1 parent b06a20f
commit b4c3c30
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Showing 4 changed files with 24 additions and 3 deletions.
diff --git a/HISTORY.rst b/HISTORY.rst
@@ -8,6 +8,7 @@ Unreleased
 ----------
 
 * [`#181 <https://github.com/mwarkentin/django-watchman/pull/181>`_] Update sample project to Django 4.x
+* [`#171 <https://github.com/mwarkentin/django-watchman/pull/171>`_] Improve database check performance: replace introspection.table_names() by a simple cursor query (@cristianemoyano)
 
 1.2.0 (2020-09-20)
 ------------------

diff --git a/tests/test_decorators.py b/tests/test_decorators.py
@@ -12,6 +12,7 @@
 import logging
 import unittest
 from unittest import mock
+from unittest.mock import MagicMock, patch
 
 from django.test.client import Client
 from django.urls import reverse
@@ -25,6 +26,21 @@ def __init__(self, *args, **kwargs):
         super(self.__class__, self).__init__(*args, **kwargs)
 
 
+class TestDBConnection(unittest.TestCase):
+    def setUp(self):
+        self.client = Client()
+
+    @patch("watchman.checks.connections")
+    def test_cursor_is_called(self, mock_connections):
+        cursor_mock = MagicMock()
+        mock_connections["default"].cursor().__enter__.return_value = cursor_mock
+        data = {
+            "watchman-token": "t1",
+        }
+        self.client.get(reverse("status"), data)
+        cursor_mock.execute.assert_called_once_with("SELECT 1")
+
+
 class TestWatchmanMultiTokens(unittest.TestCase):
     def setUp(self):
         self.client = Client()

diff --git a/tests/test_views.py b/tests/test_views.py
@@ -85,10 +85,12 @@ def test_check_database_handles_exception(self):
         )
 
     def test_check_cache_handles_exception(self):
-
         response = checks._check_cache("foo")
         self.assertFalse(response["foo"]["ok"])
-        self.assertIn(response["foo"]["error"], "The connection 'foo' doesn't exist.")
+        self.assertIn(
+            response["foo"]["error"],
+            "The connection 'foo' doesn't exist.",
+        )
 
     def test_response_skipped_checks(self):
         expected_checks = [

diff --git a/watchman/checks.py b/watchman/checks.py
@@ -38,7 +38,9 @@ def _check_databases(databases):
 
 @check
 def _check_database(database):
-    connections[database].introspection.table_names()
+    connection = connections[database]
+    with connection.cursor() as cursor:
+        cursor.execute("SELECT 1")
     return {database: {"ok": True}}
-Original file line number
+Diff line change
@@ Expand Up / @@ -8,6 +8,7 @@ Unreleased @@
     ----------
     * [`#181 <https://github.com/mwarkentin/django-watchman/pull/181>`_] Update sample project to Django 4.x
+    * [`#171 <https://github.com/mwarkentin/django-watchman/pull/171>`_] Improve database check performance: replace introspection.table_names() by a simple cursor query (@cristianemoyano)
 .2.0 (2020-09-20)
     ------------------
@@ Expand Down @@