From 716beaecb33881996fe2eee9271c3b6416af4d3a Mon Sep 17 00:00:00 2001
From: Joris Van den Bossche <jorisvandenbossche@gmail.com>
Date: Fri, 9 Sep 2022 19:18:36 +0200
Subject: [PATCH] Backport PR #48472: PERF: keep using ObjectEngine for
 ExtensionArrays for 1.5

---
 pandas/core/indexes/base.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 91c658a4cef5d..ace3df3ae97a4 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -5154,6 +5154,9 @@ def _get_engine_target(self) -> ArrayLike:
         if isinstance(vals, StringArray):
             # GH#45652 much more performant than ExtensionEngine
             return vals._ndarray
+        if type(self) is Index and isinstance(self._values, ExtensionArray):
+            # TODO(ExtensionIndex): remove special-case, just use self._values
+            return self._values.astype(object)
         return vals
 
     def _from_join_target(self, result: np.ndarray) -> ArrayLike: