From: Daniele Varrazzo <daniele.varrazzo@gmail.com>
Date: Wed, 19 Oct 2022 15:38:20 +0000 (+0100)
Subject: perf: use wait_select on Windows
X-Git-Tag: 3.1.5~7^2~12
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=46b49b6f37b4144b1f5b27c4781e15986391c2e4;p=thirdparty%2Fpsycopg.git

perf: use wait_select on Windows

On windows, the default selector strategy is select. As a consequence
using the higher level selector object comes with a performance penalty.
---

diff --git a/psycopg/psycopg/waiting.py b/psycopg/psycopg/waiting.py
index a784aaab4..3fb4cf097 100644
--- a/psycopg/psycopg/waiting.py
+++ b/psycopg/psycopg/waiting.py
@@ -214,6 +214,9 @@ async def wait_conn_async(gen: PQGenConn[RV], timeout: Optional[float] = None) -
         return rv
 
 
+# Specialised implementation of wait functions.
+
+
 def wait_select(gen: PQGen[RV], fileno: int, timeout: Optional[float] = None) -> RV:
     """
     Wait for a generator using select where supported.
@@ -297,7 +300,16 @@ def wait_epoll(gen: PQGen[RV], fileno: int, timeout: Optional[float] = None) ->
         return rv
 
 
-if selectors.DefaultSelector is getattr(selectors, "EpollSelector", None):
+# Choose the best wait strategy for the platform.
+#
+# the selectors objects have a generic interface but come with some overhead,
+# so we also offer more finely tuned implementations.
+
+if selectors.DefaultSelector is getattr(selectors, "SelectSelector", None):
+    # On Windows, SelectSelector should be the default.
+    wait = wait_select
+
+elif selectors.DefaultSelector is getattr(selectors, "EpollSelector", None):
     # NOTE: select seems more performing than epoll. It is admittedly unlikely
     # that a platform has epoll but not select, so maybe we could kill
     # wait_epoll altogether(). More testing to do.