ueshin commented on a change in pull request #25728: [SPARK-29020][WIP][SQL]
Improving array_sort behaviour
URL: https://github.com/apache/spark/pull/25728#discussion_r345375638
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/higherOrderFunctions.scala
##########
@@ -285,6 +286,113 @@ case class ArrayTransform(
override def prettyName: String = "transform"
}
+/**
+ * Sorts elements in an array using a comparator function.
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = """_FUNC_(expr, func) - Sorts the input array in ascending order.
The elements of the
+ input array must be orderable. Null elements will be placed at the end of
the returned
+ array. Since 3.0.0 also sorts and returns the array based on the given
+ comparator function. The comparator will take two nullable arguments
+ representing two nullable elements of the array.
+ It returns -1, 0, or 1 as the first nullable element is less than, equal
to, or greater
+ than the second nullable element. If the comparator function returns other
+ values (including NULL), the query will fail and raise an error.
+ """,
+ examples = """
+ Examples:
+ > SELECT _FUNC_(array(5, 6, 1), (left, right) -> If(And(IsNull(left),
IsNull(right)), 0, If(IsNull(left), 1, If(IsNull(right), -1, If(left < right,
-1, If(left > right, 1, 0))))));
+ [1,5,6]
+ > SELECT _FUNC_(array('bc', 'ab', 'dc'), (left, right) ->
If(And(IsNull(left), IsNull(right)), 0, If(IsNull(left), 1, If(IsNull(right),
-1, If(left < right, -1, If(left > right, 1, 0))))));
+ ["dc","bc","ab"]
+ > SELECT _FUNC_(array('b', 'd', null, 'c', 'a'));
+ ["a","b","c","d",null]
Review comment:
How about something like:
```diff
Examples:
- > SELECT _FUNC_(array(5, 6, 1), (left, right) -> If(And(IsNull(left),
IsNull(right)), 0, If(IsNull(left), 1, If(IsNull(right), -1, If(left < right,
-1, If(left > right, 1, 0))))));
- [1,5,6]
- > SELECT _FUNC_(array('bc', 'ab', 'dc'), (left, right) ->
If(And(IsNull(left), IsNull(right)), 0, If(IsNull(left), 1, If(IsNull(right),
-1, If(left < right, -1, If(left > right, 1, 0))))));
- ["dc","bc","ab"]
> SELECT _FUNC_(array('b', 'd', null, 'c', 'a'));
["a","b","c","d",null]
+ > SELECT _FUNC_(array(5, 6, 1), (left, right) -> case when left <
right then -1 when left > right then 1 else 0 end);
+ [1,5,6]
+ > SELECT _FUNC_(array('bc', 'ab', null, 'dc'), (left, right) -> case
when left is null and right is null then 0 when left is null then -1 when right
is null then 1 when left < right then 1 when left > right then -1 else 0 end);
+ [null,"dc","bc","ab"]
```
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