Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/15513#discussion_r85624958
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/HyperLogLogPlusPlus.scala
---
@@ -47,10 +47,16 @@ import org.apache.spark.sql.types._
*/
// scalastyle:on
@ExpressionDescription(
- usage = """_FUNC_(expr) - Returns the estimated cardinality by
HyperLogLog++.
- _FUNC_(expr, relativeSD=0.05) - Returns the estimated cardinality by
HyperLogLog++
- with relativeSD, the maximum estimation error allowed.
- """)
+ usage = """
+ _FUNC_(expr[, relativeSD]) - Returns the estimated cardinality by
HyperLogLog++.
+ `relativeSD` defines the maximum estimation error allowed.
+ """,
+ extended = """
+ Arguments:
+ expr - an expression of any type that represents data to count.
--- End diff --
```sql
spark-sql> SELECT approx_count_distinct(array(1)),
approx_count_distinct(struct(1)), approx_count_distinct(map(1,1));
1 1 1
```
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