maropu commented on a change in pull request #27836: [SPARK-31009][SQL] Support
json_object_keys function
URL: https://github.com/apache/spark/pull/27836#discussion_r396158089
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
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@@ -796,3 +797,63 @@ case class SchemaOfJson(
override def prettyName: String = "schema_of_json"
}
+
+/**
+ * A function which returns all the keys of outer JSON object.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(json_object) - returns all the keys of outer JSON object.",
+ arguments = """
+ Arguments:
+ * json_object - A JSON object is required as argument. `Null` is
returned, if an invalid JSON
+ string is given. `Runtime Exception` is thrown, if null string or
JSON array is given.
+ """,
+ examples = """
+ Examples:
+ > Select _FUNC_('{}');
+ []
+ > Select _FUNC_('{"key": "value"}');
+ ["key"]
+ > Select _FUNC_('{"f1":"abc","f2":{"f3":"a", "f4":"b"}}');
+ ["f1","f2"]
+ """,
+ since = "3.1.0")
+case class JsonObjectKeys(child: Expression) extends UnaryExpression with
CodegenFallback {
+ override def dataType: DataType = ArrayType(StringType)
+ override def nullable: Boolean = true
+ override def prettyName: String = "json_object_keys"
+
+ override def eval(input: InternalRow): Any = {
+ try {
+ lazy val json = child.eval(input).asInstanceOf[UTF8String]
Review comment:
why we need `lazy` here?
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