Add RowGroupMetaData information to cudf.io.read_parquet_metadata

python/cudf/cudf/io/parquet.py

@@ -276,8 +276,12 @@ def read_parquet_metadata(path):
     num_rows = pq_file.metadata.num_rows
     num_row_groups = pq_file.num_row_groups
     col_names = pq_file.schema.names
+    row_group_metadata = [
+        pq_file.metadata.row_group(row_group_number)
+        for row_group_number in range(num_row_groups)
+    ]
 
-    return num_rows, num_row_groups, col_names
+    return num_rows, num_row_groups, col_names, row_group_metadata
 
 
 @_cudf_nvtx_annotate

python/cudf/cudf/tests/test_parquet.py

@@ -415,7 +415,7 @@ def num_row_groups(rows, group_size):
     row_group_size = 5
     pdf.to_parquet(fname, compression="snappy", row_group_size=row_group_size)
 
-    num_rows, row_groups, col_names = cudf.io.read_parquet_metadata(fname)
+    num_rows, row_groups, col_names, _ = cudf.io.read_parquet_metadata(fname)
 
     assert num_rows == len(pdf.index)
     assert row_groups == num_row_groups(num_rows, row_group_size)
@@ -561,7 +561,7 @@ def test_parquet_read_row_groups(tmpdir, pdf, row_group_size):
     fname = tmpdir.join("row_group.parquet")
     pdf.to_parquet(fname, compression="gzip", row_group_size=row_group_size)
 
-    num_rows, row_groups, col_names = cudf.io.read_parquet_metadata(fname)
+    num_rows, row_groups, col_names, _ = cudf.io.read_parquet_metadata(fname)
 
     gdf = [cudf.read_parquet(fname, row_groups=[i]) for i in range(row_groups)]
     gdf = cudf.concat(gdf)
@@ -586,7 +586,7 @@ def test_parquet_read_row_groups_non_contiguous(tmpdir, pdf, row_group_size):
     fname = tmpdir.join("row_group.parquet")
     pdf.to_parquet(fname, compression="gzip", row_group_size=row_group_size)
 
-    num_rows, row_groups, col_names = cudf.io.read_parquet_metadata(fname)
+    num_rows, row_groups, col_names, _ = cudf.io.read_parquet_metadata(fname)
 
     # alternate rows between the two sources
     gdf = cudf.read_parquet(
@@ -2845,14 +2845,35 @@ def test_to_parquet_row_group_size(
         fname, row_group_size_bytes=size_bytes, row_group_size_rows=size_rows
     )
 
-    num_rows, row_groups, col_names = cudf.io.read_parquet_metadata(fname)
+    num_rows, row_groups, col_names, _ = cudf.io.read_parquet_metadata(fname)
     # 8 bytes per row, as the column is int64
     expected_num_rows = max(
         math.ceil(num_rows / size_rows), math.ceil(8 * num_rows / size_bytes)
     )
     assert expected_num_rows == row_groups
 
 
+@pytest.mark.parametrize("size_rows", [500_000, 100_000, 10_000])
+def test_parquet_row_group_metadata(tmpdir, large_int64_gdf, size_rows):
+    fname = tmpdir.join("row_group_size.parquet")
+    large_int64_gdf.to_parquet(fname, row_group_size_rows=size_rows)
+
+    # read file metadata from parquet
+    (
+        num_rows,
+        row_groups,
+        col_names,
+        row_group_metadata,
+    ) = cudf.io.read_parquet_metadata(fname)
+
+    # length(RowGroupsMetaData) == number of row groups
+    assert len(row_group_metadata) == row_groups
+    # sum of rows in row groups == total rows
+    assert num_rows == sum(
+        [row_group.to_dict()["num_rows"] for row_group in row_group_metadata]
+    )
+
+
 def test_parquet_reader_decimal_columns():
     df = cudf.DataFrame(
         {

python/cudf/cudf/utils/ioutils.py

@@ -101,11 +101,12 @@
 Total number of rows
 Number of row groups
 List of column names
+List of metadata of row groups
 
 Examples
 --------
 >>> import cudf
->>> num_rows, num_row_groups, names = cudf.io.read_parquet_metadata(filename)
+>>> num_rows, num_row_groups, names, row_group_metadata = cudf.io.read_parquet_metadata(filename)
 >>> df = [cudf.read_parquet(fname, row_group=i) for i in range(row_groups)]
 >>> df = cudf.concat(df)
 >>> df