feat: Support pivoting unordered, unindexed dataframe

bigframes/core/blocks.py

@@ -2129,9 +2129,17 @@ def _get_unique_values(
         import bigframes.core.block_transforms as block_tf
         import bigframes.dataframe as df
 
-        unique_value_block = block_tf.drop_duplicates(
-            self.select_columns(columns), columns
-        )
+        if self.explicitly_ordered:
+            unique_value_block = block_tf.drop_duplicates(
+                self.select_columns(columns), columns
+            )
+        else:
+            unique_value_block, _ = self.aggregate(by_column_ids=columns, dropna=False)
+            col_labels = self._get_labels_for_columns(columns)
+            unique_value_block = unique_value_block.reset_index(
+                drop=False
+            ).with_column_labels(col_labels)
+
         pd_values = (
             df.DataFrame(unique_value_block).head(max_unique_values + 1).to_pandas()
         )

bigframes/dataframe.py

@@ -3346,8 +3346,6 @@ def _pivot(
         )
         return DataFrame(pivot_block)
 
-    @validations.requires_index
-    @validations.requires_ordering()
     def pivot(
         self,
         *,
@@ -3361,8 +3359,6 @@ def pivot(
     ) -> DataFrame:
         return self._pivot(columns=columns, index=index, values=values)
 
-    @validations.requires_index
-    @validations.requires_ordering()
     def pivot_table(
         self,
         values: typing.Optional[

tests/system/conftest.py

@@ -585,6 +585,18 @@ def scalars_df_null_index(
     ).sort_values("rowindex")
 
 
+@pytest.fixture(scope="session")
+def scalars_df_unordered(
+    scalars_table_id: str, unordered_session: bigframes.Session
+) -> bigframes.dataframe.DataFrame:
+    """DataFrame pointing at test data."""
+    df = unordered_session.read_gbq(
+        scalars_table_id, index_col=bigframes.enums.DefaultIndexKind.NULL
+    )
+    assert not df._block.explicitly_ordered
+    return df
+
+
 @pytest.fixture(scope="session")
 def scalars_df_2_default_index(
     scalars_df_2_index: bigframes.dataframe.DataFrame,

tests/system/small/test_unordered.py

@@ -265,3 +265,27 @@ def test__resample_with_index(unordered_session, rule, origin, data):
     pd.testing.assert_frame_equal(
         bf_result, pd_result, check_dtype=False, check_index_type=False
     )
+
+
+@pytest.mark.parametrize(
+    ("values", "index", "columns"),
+    [
+        ("int64_col", "int64_too", ["string_col"]),
+        (["int64_col"], "int64_too", ["string_col"]),
+        (["int64_col", "float64_col"], "int64_too", ["string_col"]),
+    ],
+)
+def test_unordered_df_pivot(
+    scalars_df_unordered, scalars_pandas_df_index, values, index, columns
+):
+    bf_result = scalars_df_unordered.pivot(
+        values=values, index=index, columns=columns
+    ).to_pandas()
+    pd_result = scalars_pandas_df_index.pivot(
+        values=values, index=index, columns=columns
+    )
+
+    # Pandas produces NaN, where bq dataframes produces pd.NA
+    bf_result = bf_result.fillna(float("nan"))
+    pd_result = pd_result.fillna(float("nan"))
+    pd.testing.assert_frame_equal(bf_result, pd_result, check_dtype=False)