From dfc3f899e5b81997a343b227100781f4c39a3464 Mon Sep 17 00:00:00 2001
From: Rongrong <i@rong.moe>
Date: Sun, 12 Nov 2023 20:55:13 +0800
Subject: [PATCH] Skip filtering ``CookieJar`` when the jar is empty or all
 cookies have expired (#7819)

The filtering itself and its preparation in `CookieJar.filter_cookies()`
is expensive. Sometimes there are no cookies in the jar or all cookies
have expired. Skip filtering and its preparation in this case.

Because the empty check is much cheaper than `_do_expiration()`, I think
it deserves to be duplicated before and after calling
`_do_expiration()`.

```console
$ python3.11 -m timeit -s 'from collections import defaultdict; d=defaultdict(foo="bar")' \
> 'if not d: pass'
50000000 loops, best of 5: 8.3 nsec per loop
$ python3.11 -m timeit -s 'from collections import defaultdict; d=defaultdict()' \
> 'if not d: pass'
50000000 loops, best of 5: 8.74 nsec per loop
$ python3.11 -m timeit -s 'from aiohttp import CookieJar; cj = CookieJar()' \
> 'cj._do_expiration()'
200000 loops, best of 5: 1.86 usec per loop
```
---
 CHANGES/7819.feature | 1 +
 CONTRIBUTORS.txt     | 1 +
 aiohttp/cookiejar.py | 8 +++++++-
 3 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 CHANGES/7819.feature

diff --git a/CHANGES/7819.feature b/CHANGES/7819.feature
new file mode 100644
index 00000000000..6ff263abeb8
--- /dev/null
+++ b/CHANGES/7819.feature
@@ -0,0 +1 @@
+Skip filtering ``CookieJar`` when the jar is empty or all cookies have expired.
diff --git a/CONTRIBUTORS.txt b/CONTRIBUTORS.txt
index b9052c404dd..539a8807689 100644
--- a/CONTRIBUTORS.txt
+++ b/CONTRIBUTORS.txt
@@ -282,6 +282,7 @@ Robert Lu
 Robert Nikolich
 Roman Markeloff
 Roman Podoliaka
+Rong Zhang
 Samir Akarioh
 Samuel Colvin
 Sean Hunt
diff --git a/aiohttp/cookiejar.py b/aiohttp/cookiejar.py
index a35c15f344b..11ef9e288a7 100644
--- a/aiohttp/cookiejar.py
+++ b/aiohttp/cookiejar.py
@@ -234,7 +234,6 @@ def filter_cookies(
         self, request_url: URL = URL()
     ) -> Union["BaseCookie[str]", "SimpleCookie[str]"]:
         """Returns this jar's cookies filtered by their attributes."""
-        self._do_expiration()
         if not isinstance(request_url, URL):
             warnings.warn(
                 "The method accepts yarl.URL instances only, got {}".format(
@@ -246,6 +245,13 @@ def filter_cookies(
         filtered: Union["SimpleCookie[str]", "BaseCookie[str]"] = (
             SimpleCookie() if self._quote_cookie else BaseCookie()
         )
+        if not self._cookies:
+            # Skip do_expiration() if there are no cookies.
+            return filtered
+        self._do_expiration()
+        if not self._cookies:
+            # Skip rest of function if no non-expired cookies.
+            return filtered
         hostname = request_url.raw_host or ""
         request_origin = URL()
         with contextlib.suppress(ValueError):