Fix stats filter

Odd things happen if you pass a one-element NDarray...

fastparquet/api.py

@@ -659,14 +659,18 @@ def filter_val(op, val, vmin=None, vmax=None):
     -------
     True or False
     """
-    if vmin is not None:
+    if vmax is not None:
+        if isinstance(vmax, np.ndarray):
+            vmax = vmax[0]
         if op in ['==', '>='] and val > vmax:
             return True
         if op == '>' and val >= vmax:
             return True
         if op == 'in' and min(val) > vmax:
             return True
-    if vmax is not None:
+    if vmin is not None:
+        if isinstance(vmin, np.ndarray):
+            vmin = vmin[0]
         if op in ['==', '<='] and val < vmin:
             return True
         if op == '<' and val <= vmin:

fastparquet/test/test_api.py

@@ -206,3 +206,13 @@ def test_filter_special(tempdir):
     out = pf.to_pandas(filters=[('symbol', '==', 'NOW')])
     assert out.x.tolist() == [1, 5, 6]
     assert out.symbol.tolist() == ['NOW', 'NOW', 'NOW']
+
+
+def test_filter_stats(tempdir):
+    df = pd.DataFrame({
+        'x': [1, 2, 3, 4, 5, 6, 7],
+    })
+    write(tempdir, df, file_scheme='hive', row_group_offsets=[0, 4])
+    pf = ParquetFile(tempdir)
+    out = pf.to_pandas(filters=[('x', '>=', 5)])
+    assert out.x.tolist() == [5, 6, 7]