[
https://issues.apache.org/jira/browse/SPARK-39893?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Wan Kun updated SPARK-39893:
----------------------------
Description:
If all group expressions are foldable, the result of this aggregate will always
be OneRowRelation.
And if all aggregate expressions are foldable, we can add limit 1 to the child
plan.
For example:
Table :
{code:sql}
create table tab(key int, value string) using parquet
{code}
Query :
{code:sql}
SELECT distinct 1001 as id , cast('2022-06-03' as date) AS DT
FROM testData
{code}
can change to
{code:sql}
SELECT distinct 1001 as id , cast('2022-06-03' as date) AS DT
FROM (
SELECT *
FROM tab
LIMIT 1
)
{code}
Query:
{code:sql}
SELECT 1001 AS id, cast('2022-06-03' as date) AS DT
FROM tab
group by 'x'
{code}
is equal to
{code:sql}
SELECT 1001 AS id, cast('2022-06-03' as date) AS DT
FROM (
SELECT *
FROM tab
LIMIT 1
)
group by 'x'
{code}
was:
If all groupingExpressions and aggregateExpressions in a aggregate are
foldable, we can remove this aggregate.
For example, query :
{code:java}
SELECT distinct 1001 as id , cast('2022-06-03' as date) AS DT FROM testData
{code}
the grouping expressions are : *[1001, 2022-06-03]*
the aggregate expressions are : *[1001 AS id#274, 2022-06-03 AS DT#275]*
so we can skip scan table testData and remote the aggregate operation.
Before this PR:
{code:java}
Aggregate [1001, 2022-06-03], [1001 AS id#274, 2022-06-03 AS DT#275],
Statistics(sizeInBytes=16.0 EiB)
+- SerializeFromObject, Statistics(sizeInBytes=8.0 EiB)
+- ExternalRDD [obj#12], Statistics(sizeInBytes=8.0 EiB)
{code}
After this PR:
{code:java}
Project [1001 AS id#218, 2022-06-03 AS DT#219], Statistics(sizeInBytes=2.0 B)
+- OneRowRelation, Statistics(sizeInBytes=1.0 B)
{code}
> Push limit 1 to the aggregate's child plan if grouping expressions and
> aggregate expressions are foldable
> ---------------------------------------------------------------------------------------------------------
>
> Key: SPARK-39893
> URL: https://issues.apache.org/jira/browse/SPARK-39893
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.4.0
> Reporter: Wan Kun
> Priority: Major
>
> If all group expressions are foldable, the result of this aggregate will
> always be OneRowRelation.
> And if all aggregate expressions are foldable, we can add limit 1 to the
> child plan.
> For example:
> Table :
> {code:sql}
> create table tab(key int, value string) using parquet
> {code}
> Query :
> {code:sql}
> SELECT distinct 1001 as id , cast('2022-06-03' as date) AS DT
> FROM testData
> {code}
> can change to
> {code:sql}
> SELECT distinct 1001 as id , cast('2022-06-03' as date) AS DT
> FROM (
> SELECT *
> FROM tab
> LIMIT 1
> )
> {code}
> Query:
> {code:sql}
> SELECT 1001 AS id, cast('2022-06-03' as date) AS DT
> FROM tab
> group by 'x'
> {code}
> is equal to
> {code:sql}
> SELECT 1001 AS id, cast('2022-06-03' as date) AS DT
> FROM (
> SELECT *
> FROM tab
> LIMIT 1
> )
> group by 'x'
> {code}
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