dongjoon-hyun commented on a change in pull request #27759: [SPARK-31008][SQL]
Support json_array_length function
URL: https://github.com/apache/spark/pull/27759#discussion_r400587840
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
##########
@@ -781,3 +781,68 @@ case class SchemaOfJson(
override def prettyName: String = "schema_of_json"
}
+
+/**
+ * A function that returns the number of elements in outer JSON array.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(jsonArray) - Returns the number of elements in outer JSON
array.",
+ arguments = """
+ Arguments:
+ * jsonArray - A JSON array. An Exception is thrown if any other valid
JSON strings are passed.
+ `NULL` is returned in case of invalid JSON.
+ """,
+ examples = """
+ Examples:
+ > SELECT _FUNC_('[1,2,3,4]');
+ 4
+ > SELECT _FUNC_('[1,2,3,{"f1":1,"f2":[5,6]},4]');
+ 5
+ > SELECT _FUNC_('[1,2');
+ NULL
+ """,
+ since = "3.1.0"
+)
+case class LengthOfJsonArray(child: Expression)
+ extends UnaryExpression with CodegenFallback {
+ override def dataType: DataType = IntegerType
+ override def nullable: Boolean = true
+ override def prettyName: String = "json_array_length"
+
+ override def eval(input: InternalRow): Any = {
+ val json = child.eval(input).asInstanceOf[UTF8String]
Review comment:
Hi, @iRakson . Please use `ExpectsInputTypes` to prevent
`ClassCastException` like the following.
```
spark-sql> SELECT json_array_length(1);
20/03/30 18:19:11 ERROR SparkSQLDriver: Failed in [SELECT
json_array_length(1)]
java.lang.ClassCastException: class java.lang.Integer cannot be cast to
class org.apache.spark.unsafe.types.UTF8String (java.lang.Integer is in module
java.base of loader 'bootstrap'; org.apache.spark.unsafe.types.UTF8String is in
unnamed module of loader 'app')
```
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