From 30d321557285bfbf63452d0e145f7a7b1b1db02d Mon Sep 17 00:00:00 2001
From: warm200 <wm140906@gmail.com>
Date: Fri, 17 Jun 2022 11:14:52 -0400
Subject: [PATCH] PERF: Performance improvement on dataframe.update. setitem is
 doing copy under the hood and it's not updated in place

---
 pandas/core/frame.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 39a940169e1f3..8711d53353185 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -8000,7 +8000,7 @@ def update(
             if mask.all():
                 continue
 
-            self[col] = expressions.where(mask, this, that)
+            self.loc[:, col] = expressions.where(mask, this, that)
 
     # ----------------------------------------------------------------------
     # Data reshaping