From 25c579ae48c88c16bbe54607ae536f2852c72d23 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Mon, 19 Jun 2023 22:07:38 +0200
Subject: [PATCH] BUG: IntervalIndex.get_indexer raising for read only array
 (#53703)

---
 doc/source/whatsnew/v2.1.0.rst                 |  2 +-
 pandas/_libs/intervaltree.pxi.in               |  4 ++--
 pandas/tests/indexes/interval/test_indexing.py | 11 +++++++++++
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/doc/source/whatsnew/v2.1.0.rst b/doc/source/whatsnew/v2.1.0.rst
index 3c4ca23797f2c..64df847aa74f0 100644
--- a/doc/source/whatsnew/v2.1.0.rst
+++ b/doc/source/whatsnew/v2.1.0.rst
@@ -401,7 +401,7 @@ Strings
 
 Interval
 ^^^^^^^^
--
+- :meth:`pd.IntervalIndex.get_indexer` and :meth:`pd.IntervalIndex.get_indexer_nonunique` raising if ``target`` is read-only array (:issue:`53703`)
 -
 
 Indexing
diff --git a/pandas/_libs/intervaltree.pxi.in b/pandas/_libs/intervaltree.pxi.in
index 67fee7c5fbadd..0b99aebbd3816 100644
--- a/pandas/_libs/intervaltree.pxi.in
+++ b/pandas/_libs/intervaltree.pxi.in
@@ -125,7 +125,7 @@ cdef class IntervalTree(IntervalMixin):
         sort_order = self.left_sorter
         return is_monotonic(sort_order, False)[0]
 
-    def get_indexer(self, scalar_t[:] target) -> np.ndarray:
+    def get_indexer(self, ndarray[scalar_t, ndim=1] target) -> np.ndarray:
         """Return the positions corresponding to unique intervals that overlap
         with the given array of scalar targets.
         """
@@ -153,7 +153,7 @@ cdef class IntervalTree(IntervalMixin):
             old_len = result.data.n
         return result.to_array().astype('intp')
 
-    def get_indexer_non_unique(self, scalar_t[:] target):
+    def get_indexer_non_unique(self, ndarray[scalar_t, ndim=1] target):
         """Return the positions corresponding to intervals that overlap with
         the given array of scalar targets. Non-unique positions are repeated.
         """
diff --git a/pandas/tests/indexes/interval/test_indexing.py b/pandas/tests/indexes/interval/test_indexing.py
index e7db8076efa2b..e65ae52e348c6 100644
--- a/pandas/tests/indexes/interval/test_indexing.py
+++ b/pandas/tests/indexes/interval/test_indexing.py
@@ -424,6 +424,17 @@ def test_get_indexer_interval_index(self, box):
         expected = np.array([-1, -1, -1], dtype=np.intp)
         tm.assert_numpy_array_equal(actual, expected)
 
+    def test_get_indexer_read_only(self):
+        idx = interval_range(start=0, end=5)
+        arr = np.array([1, 2])
+        arr.flags.writeable = False
+        result = idx.get_indexer(arr)
+        expected = np.array([0, 1])
+        tm.assert_numpy_array_equal(result, expected, check_dtype=False)
+
+        result = idx.get_indexer_non_unique(arr)[0]
+        tm.assert_numpy_array_equal(result, expected, check_dtype=False)
+
 
 class TestSliceLocs:
     def test_slice_locs_with_interval(self):