Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/15513#discussion_r85624910
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/First.scala
---
@@ -29,10 +29,16 @@ import org.apache.spark.sql.types._
* a single partition, and we use a single reducer to do the aggregation.).
*/
@ExpressionDescription(
- usage = """_FUNC_(expr) - Returns the first value of `child` for a group
of rows.
- _FUNC_(expr,isIgnoreNull=false) - Returns the first value of `child`
for a group of rows.
- If isIgnoreNull is true, returns only non-null values.
- """)
+ usage = """
+ _FUNC_(expr[, isIgnoreNull]) - Returns the first value of `expr` for a
group of rows.
+ If `isIgnoreNull` is true, returns only non-null values.
+ """,
+ extended = """
+ Arguments:
+ expr - an expression of any type that represents data to collect the
first.
--- End diff --
```sql
spark-sql> SELECT first(array(1)), first(struct(1)), first(map(1,1));
[1] {"col1":1} {1:1}
```
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