yaooqinn commented on a change in pull request #26371: [SPARK-27976][SQL] Add
built-in Array Functions: array_append
URL: https://github.com/apache/spark/pull/26371#discussion_r341942785
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
##########
@@ -3928,3 +3928,128 @@ case class ArrayExcept(left: Expression, right:
Expression) extends ArrayBinaryL
override def prettyName: String = "array_except"
}
+
+@ExpressionDescription(
+ usage = """
+ _FUNC_(array, element) - Returns an array of appending an element to the end
of an array
+ """,
+ examples = """
+ Examples:
+ > SELECT _FUNC_(array(1, 2, 3), 3);
+ [1,2,3,3]
+ > SELECT _FUNC_(array(1, 2, 3), null);
+ [1,2,3,null]
+ > SELECT _FUNC_(a, e) FROM VALUES (array(1,2), 3), (array(3, 4), null),
(null, 3) tbl(a, e);
+ NULL
+ [1,2,3]
+ [3,4,null]
+ """,
+ since = "3.0.0")
+case class ArrayAppend(left: Expression, right: Expression) extends
BinaryExpression {
Review comment:
Hi @maropu , the key difference is when the array is null and the new
element is not, array_append will create new array but concat's result will be
null. please see the following cases.
```
-- !query 18
select array_append(a, e) from VALUES (array(1,2), 3), (array(3, 4), null),
(null, 3), (null, null) tbl(a, e)
-- !query 18 schema
struct<array_append(a, e):array<int>>
-- !query 18 output
NULL
[1,2,3]
[3,4,null]
[3]
-- !query 19
select concat(a, array(e)) from VALUES (array(1,2), 3), (array(3, 4), null),
(null, 3), (null, null) tbl(a, e)
-- !query 19 schema
struct<concat(a, array(e)):array<int>>
-- !query 19 output
NULL
NULL
[1,2,3]
[3,4,null]
```
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