MaxGekk 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_r387493158
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
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@@ -781,3 +782,65 @@ case class SchemaOfJson(
override def prettyName: String = "schema_of_json"
}
+
+/**
+ * A function that returns number of elements in outer Json Array.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(jsonArray) - Returns length of the jsonArray",
+ arguments = """
+ jsonArray - A JSON array is required as argument. `Analysis Exception` is
thrown if any other
+ valid JSON expression is 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)
Review comment:
The semantic of `LengthOfJsonArray` is similar to `Size` + `JsonToStructs`.
What about to extend `RuntimeReplaceable` and map `LengthOfJsonArray` to the
combination of existing expressions.
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