cloud-fan commented on a change in pull request #30144:
URL: https://github.com/apache/spark/pull/30144#discussion_r611420882
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File path: docs/sql-ref-syntax-qry-select-groupby.md
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@@ -93,6 +95,25 @@ aggregate_name ( [ DISTINCT ] expression [ , ... ] ) [
FILTER ( WHERE boolean_ex
(product, warehouse, location), (warehouse), (product), (warehouse,
product), ())`.
The N elements of a `CUBE` specification results in 2^N `GROUPING SETS`.
+* **Mixed Grouping Analytics**
+
+ A GROUP BY clause can include multiple `group_expression`s and multiple
`CUBE|ROLLUP|GROUPING SETS`s.
+ `CUBE|ROLLUP` is just a syntax sugar for `GROUPING SETS`, please refer to
the sections above for
+ how to translate `CUBE|ROLLUP` to `GROUPING SETS`. `group_expression` can
be treated as a single-group
+ `GROUPING SETS` under this context. For multiple `GROUPING SETS` in the
`GROUP BY` clause, we generate
+ a single `GROUPING SETS` by doing a cross-product of the original
`GROUPING SETS`s. For example,
+ `GROUP BY warehouse, GROUPING SETS((product), ()), GROUPING
SETS((location, size), (location), (size), ())`
+ and `GROUP BY warehouse, ROLLUP(warehouse), CUBE(location, size)` is
equivalent to
Review comment:
typo? `ROLLUP(warehouse)` -> `ROLLUP(product)`
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