BUG: .get_indexer_non_unique() must return an array of ints (#44084)

doc/source/whatsnew/v1.4.0.rst

@@ -515,7 +515,7 @@ Strings
 
 Interval
 ^^^^^^^^
--
+- Bug in :meth:`IntervalIndex.get_indexer_non_unique` returning boolean mask instead of array of integers for a non unique and non monotonic index (:issue:`44084`)
 -
 
 Indexing

pandas/core/indexes/interval.py

@@ -727,6 +727,8 @@ def _get_indexer_pointwise(
  if isinstance(locs, slice):
  # Only needed for get_indexer_non_unique
  locs = np.arange(locs.start, locs.stop, locs.step, dtype="intp")
+ elif not self.is_unique and not self.is_monotonic:
+ locs = np.where(locs)[0]
  locs = np.array(locs, ndmin=1)
  except KeyError:
  missing.append(i)

pandas/tests/indexes/interval/test_indexing.py

@@ -8,8 +8,10 @@
 from pandas import (
  NA,
  CategoricalIndex,
+ Index,
  Interval,
  IntervalIndex,
+ MultiIndex,
  NaT,
  Timedelta,
  date_range,
@@ -373,6 +375,31 @@ def test_get_indexer_with_nans(self):
  expected = np.array([0, 1], dtype=np.intp)
  tm.assert_numpy_array_equal(result, expected)
 
+ def test_get_index_non_unique_non_monotonic(self):
+ # GH#44084 (root cause)
+ index = IntervalIndex.from_tuples(
+ [(0.0, 1.0), (1.0, 2.0), (0.0, 1.0), (1.0, 2.0)]
+ )
+
+ result, _ = index.get_indexer_non_unique([Interval(1.0, 2.0)])
+ expected = np.array([1, 3], dtype=np.intp)
+ tm.assert_numpy_array_equal(result, expected)
+
+ def test_get_indexer_multiindex_with_intervals(self):
+ # GH#44084 (MultiIndex case as reported)
+ interval_index = IntervalIndex.from_tuples(
+ [(2.0, 3.0), (0.0, 1.0), (1.0, 2.0)], name="interval"
+ )
+ foo_index = Index([1, 2, 3], name="foo")
+
+ multi_index = MultiIndex.from_product([foo_index, interval_index])
+
+ result = multi_index.get_level_values("interval").get_indexer_for(
+ [Interval(0.0, 1.0)]
+ )
+ expected = np.array([1, 4, 7], dtype=np.intp)
+ tm.assert_numpy_array_equal(result, expected)
+
 
 class TestSliceLocs:
  def test_slice_locs_with_interval(self):