cloud-fan commented on a change in pull request #27428:
URL: https://github.com/apache/spark/pull/27428#discussion_r453513546
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/RewriteDistinctAggregates.scala
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@@ -102,23 +102,126 @@ import org.apache.spark.sql.types.IntegerType
* {{{
* Aggregate(
* key = ['key]
- * functions = [count(if (('gid = 1)) 'cat1 else null),
- * count(if (('gid = 2)) 'cat2 else null),
+ * functions = [count(if (('gid = 1)) '_gen_attr_1 else null),
+ * count(if (('gid = 2)) '_gen_attr_2 else null),
* first(if (('gid = 0)) 'total else null) ignore nulls]
* output = ['key, 'cat1_cnt, 'cat2_cnt, 'total])
* Aggregate(
- * key = ['key, 'cat1, 'cat2, 'gid]
- * functions = [sum('value) with FILTER('id > 1)]
- * output = ['key, 'cat1, 'cat2, 'gid, 'total])
+ * key = ['key, '_gen_attr_1, '_gen_attr_2, 'gid]
+ * functions = [sum('_gen_attr_3)]
+ * output = ['key, '_gen_attr_1, '_gen_attr_2, 'gid, 'total])
* Expand(
- * projections = [('key, null, null, 0, cast('value as bigint), 'id),
+ * projections = [('key, null, null, 0, if ('id > 1) cast('value as
bigint) else null, 'id),
* ('key, 'cat1, null, 1, null, null),
* ('key, null, 'cat2, 2, null, null)]
- * output = ['key, 'cat1, 'cat2, 'gid, 'value, 'id])
+ * output = ['key, '_gen_attr_1, '_gen_attr_2, 'gid, '_gen_attr_3, 'id])
+ * LocalTableScan [...]
+ * }}}
+ *
+ * Third example: single distinct aggregate function with filter clauses and
have
+ * not other distinct aggregate function (in sql):
+ * {{{
+ * SELECT
+ * COUNT(DISTINCT cat1) FILTER (WHERE id > 1) as cat1_cnt,
+ * SUM(value) AS total
+ * FROM
+ * data
+ * GROUP BY
+ * key
+ * }}}
+ *
+ * This translates to the following (pseudo) logical plan:
+ * {{{
+ * Aggregate(
+ * key = ['key]
+ * functions = [COUNT(DISTINCT 'cat1) with FILTER('id > 1),
+ * sum('value)]
+ * output = ['key, 'cat1_cnt, 'total])
+ * LocalTableScan [...]
Review comment:
Do we need to rewrite this query? The planner can handle single distinct
agg func AFAIK.
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