| Aggregate [a#0, b#0, spark_grouping_id#0L], [a#0, b#0, count(1) AS count#0L] | |
| +- Expand [[id#0L, a#0, b#0, a#0, b#0, 0], [id#0L, a#0, b#0, a#0, null, 1], [id#0L, a#0, b#0, null, b#0, 2], [id#0L, a#0, b#0, null, null, 3]], [id#0L, a#0, b#0, a#0, b#0, spark_grouping_id#0L] | |
| +- Project [id#0L, a#0, b#0, a#0 AS a#0, b#0 AS b#0] | |
| +- LocalRelation <empty>, [id#0L, a#0, b#0] |