From f4b55c28317b43bddec9f0c006808e574940a6cd Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <patrick_hoefler@gmx.net>
Date: Wed, 18 Jan 2023 19:56:49 +0100
Subject: [PATCH 1/3] PERF: Avoid re-computing mask in nanmedian

---
 doc/source/whatsnew/v2.0.0.rst |  1 +
 pandas/core/nanops.py          | 13 ++++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/doc/source/whatsnew/v2.0.0.rst b/doc/source/whatsnew/v2.0.0.rst
index 1a071ab978de9..b5df05cce8003 100644
--- a/doc/source/whatsnew/v2.0.0.rst
+++ b/doc/source/whatsnew/v2.0.0.rst
@@ -870,6 +870,7 @@ Performance improvements
 - Performance improvement in :func:`read_html` when there are multiple tables (:issue:`49929`)
 - Performance improvement in :func:`to_datetime` when using ``'%Y%m%d'`` format (:issue:`17410`)
 - Performance improvement in :func:`to_datetime` when format is given or can be inferred (:issue:`50465`)
+- Performance improvement in :meth:`Series.median` for nullable dtypes (:issue:`1`)
 - Performance improvement in :func:`read_csv` when passing :func:`to_datetime` lambda-function to ``date_parser`` and inputs have mixed timezone offsetes (:issue:`35296`)
 - Performance improvement in :meth:`.SeriesGroupBy.value_counts` with categorical dtype (:issue:`46202`)
 - Fixed a reference leak in :func:`read_hdf` (:issue:`37441`)
diff --git a/pandas/core/nanops.py b/pandas/core/nanops.py
index 02372356d3fe4..4cba1e41d1a63 100644
--- a/pandas/core/nanops.py
+++ b/pandas/core/nanops.py
@@ -746,16 +746,19 @@ def nanmedian(values, *, axis: AxisInt | None = None, skipna: bool = True, mask=
     2.0
     """
 
-    def get_median(x):
-        mask = notna(x)
-        if not skipna and not mask.all():
+    def get_median(x, _mask):
+        if _mask is None:
+            _mask = notna(x)
+        else:
+            _mask = ~_mask
+        if not skipna and not _mask.all():
             return np.nan
         with warnings.catch_warnings():
             # Suppress RuntimeWarning about All-NaN slice
             warnings.filterwarnings(
                 "ignore", "All-NaN slice encountered", RuntimeWarning
             )
-            res = np.nanmedian(x[mask])
+            res = np.nanmedian(x[_mask])
         return res
 
     values, mask, dtype, _, _ = _get_values(values, skipna, mask=mask)
@@ -796,7 +799,7 @@ def get_median(x):
 
     else:
         # otherwise return a scalar value
-        res = get_median(values) if notempty else np.nan
+        res = get_median(values, mask) if notempty else np.nan
     return _wrap_results(res, dtype)
 
 

From 60d63716d225054bd296d48fb3b931dbf51dead6 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <patrick_hoefler@gmx.net>
Date: Wed, 18 Jan 2023 19:57:33 +0100
Subject: [PATCH 2/3] Add gh ref

---
 doc/source/whatsnew/v2.0.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v2.0.0.rst b/doc/source/whatsnew/v2.0.0.rst
index b5df05cce8003..9366404445fb2 100644
--- a/doc/source/whatsnew/v2.0.0.rst
+++ b/doc/source/whatsnew/v2.0.0.rst
@@ -870,7 +870,7 @@ Performance improvements
 - Performance improvement in :func:`read_html` when there are multiple tables (:issue:`49929`)
 - Performance improvement in :func:`to_datetime` when using ``'%Y%m%d'`` format (:issue:`17410`)
 - Performance improvement in :func:`to_datetime` when format is given or can be inferred (:issue:`50465`)
-- Performance improvement in :meth:`Series.median` for nullable dtypes (:issue:`1`)
+- Performance improvement in :meth:`Series.median` for nullable dtypes (:issue:`50838`)
 - Performance improvement in :func:`read_csv` when passing :func:`to_datetime` lambda-function to ``date_parser`` and inputs have mixed timezone offsetes (:issue:`35296`)
 - Performance improvement in :meth:`.SeriesGroupBy.value_counts` with categorical dtype (:issue:`46202`)
 - Fixed a reference leak in :func:`read_hdf` (:issue:`37441`)

From 55532e273fcbabca5e4605879a78eef6dd890440 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <patrick_hoefler@gmx.net>
Date: Wed, 18 Jan 2023 21:28:12 +0100
Subject: [PATCH 3/3] Fix

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

diff --git a/pandas/core/nanops.py b/pandas/core/nanops.py
index 4cba1e41d1a63..61f1bcdef9568 100644
--- a/pandas/core/nanops.py
+++ b/pandas/core/nanops.py
@@ -746,7 +746,7 @@ def nanmedian(values, *, axis: AxisInt | None = None, skipna: bool = True, mask=
     2.0
     """
 
-    def get_median(x, _mask):
+    def get_median(x, _mask=None):
         if _mask is None:
             _mask = notna(x)
         else: