fix(types): fix histogram bin allocation

ibis/backends/tests/test_numeric.py

@@ -1370,7 +1370,7 @@ def test_clip(backend, alltypes, df, ibis_func, pandas_func):
     backend.assert_series_equal(result, expected, check_names=False)
 
 
-@pytest.mark.notimpl(["polars"], raises=com.OperationNotDefinedError)
+@pytest.mark.notimpl(["datafusion", "polars"], raises=com.OperationNotDefinedError)
 @pytest.mark.notyet(
     ["druid"],
     raises=PyDruidProgrammingError,
@@ -1382,6 +1382,15 @@ def test_histogram(con, alltypes):
     vc = hist.value_counts().sort_index()
     vc_np, _bin_edges = np.histogram(alltypes.int_col.execute(), bins=n)
     assert vc.tolist() == vc_np.tolist()
+    assert (
+        con.execute(
+            ibis.memtable({"value": range(100)})
+            .select(bin=_.value.histogram(10))
+            .value_counts()
+            .bin_count.nunique()
+        )
+        == 1
+    )
 
 
 @pytest.mark.parametrize("const", ["pi", "e"])

ibis/expr/types/numeric.py

@@ -996,16 +996,19 @@
                 f"Cannot pass both `nbins` (got {nbins}) and `binwidth` (got {binwidth})"
             )
 
-        if binwidth is None or base is None:
+        if base is None:
+            base = self.min() - eps
+
+        if binwidth is None:
             if nbins is None:
                 raise ValueError("`nbins` is required if `binwidth` is not provided")
 
-            if base is None:
-                base = self.min() - eps
-
             binwidth = (self.max() - base) / nbins
 
-        return ((self - base) / binwidth).floor()
+        if nbins is None:
+            nbins = ((self.max() - base) / binwidth).ceil()
+
+        return ((self - base) / binwidth).floor().clip(-1, nbins - 1)
 
 
 @public