fix: support within_group #16538
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fix: support within_group #16538
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findepi
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Jun 25, 2025
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| SELECT array_agg(DISTINCT a_varchar) within group (order by a_varchar) | ||
| FROM (VALUES ('a'), ('d'), ('c'), ('a')) t(a_varchar); |
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There is no reason for this not to work. Equivalent syntax is already supported:
DataFusion CLI v48.0.0
> SELECT array_agg(DISTINCT a_varchar order by a_varchar)
FROM (VALUES ('a'), ('d'), ('c'), ('a')) t(a_varchar);
+-----------------------------------------------------------------------+
| array_agg(DISTINCT t.a_varchar) ORDER BY [t.a_varchar ASC NULLS LAST] |
+-----------------------------------------------------------------------+
| [a, c, d] |
+-----------------------------------------------------------------------+
... and not only in DataFusion
trino> SELECT array_agg(DISTINCT a_varchar order by a_varchar)
-> FROM (VALUES ('a'), ('d'), ('c'), ('a')) t(a_varchar);;
_col0
-----------
[a, c, d]
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I updated this PR to support this feature.
datafusion/sql/src/expr/function.rs
Outdated
| @@ -375,6 +375,10 @@ impl<S: ContextProvider> SqlToRel<'_, S> { | |||
| return plan_err!("WITHIN GROUP clause is required when calling ordered set aggregate function({})", fm.name()); | |||
| } | |||
|
|
|||
| if !fm.is_ordered_set_aggregate() && !within_group.is_empty() { | |||
| return plan_err!("WITHIN GROUP clause is not permitted for non-ordered set aggregate function({})", fm.name()); | |||
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array_agg is definitely ordered, or order-sensitive
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I think order-sensitive means order is necessary. but for array_agg, order is optional.
Can you please add both test queries from the issue description? Thanks! |
chenkovsky
changed the title
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Which issue does this PR close?
WITHIN GROUPclause gets ignored #16515.Rationale for this change
WITHIN GROUP clause gets ignored for non ordered aggregate function
What changes are included in this PR?
reject WITHIN GROUP clause. I checked Postgres, it also doesn't support such query. if anyone thinks that this query should be supported. I can modify thir PR to support it.
Are these changes tested?
UT
Are there any user-facing changes?
No