iRakson 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_r403847787
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/jsonExpressions.scala
##########
@@ -796,3 +796,75 @@ case class SchemaOfJson(
override def prettyName: String = "schema_of_json"
}
+
+/**
+ * A function that returns the number of elements in the outmost JSON array.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(jsonArray) - Returns the number of elements in the outmost
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 `NULL` or an 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 with ExpectsInputTypes {
+
+ override def inputTypes: Seq[DataType] = Seq(StringType)
+ 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]
+ // return null for null input
+ if (json == null) {
+ return null
+ }
+
+ try {
+
Utils.tryWithResource(CreateJacksonParser.utf8String(SharedFactory.jsonFactory,
json)) {
+ parser => {
+ // return null if null array is encountered.
+ if (parser.nextToken() == null) {
+ return null
+ }
+ // Parse the array to compute its length.
+ parseCounter(parser, input)
+ }
+ }
+ } catch {
+ case _: JsonProcessingException | _: IOException => null
+ }
+ }
+
+ private def parseCounter(parser: JsonParser, input: InternalRow): Int = {
+ var length = 0
+ // Only JSON array are supported for this function.
+ if (parser.currentToken != JsonToken.START_ARRAY) {
+ throw new IllegalArgumentException(s"$prettyName can only be called on
JSON array.")
+ }
+ // Keep traversing until the end of JSON array
+ while(parser.nextToken() != JsonToken.END_ARRAY) {
+ // Null indicates end of input.
+ if (parser.currentToken == null) {
+ throw new IllegalArgumentException("Please provide a valid JSON
array.")
Review comment:
Yeah. It is unreachable code. Because if we encounter null before
`END_ARRAY` then our JSON is invalid. I will remove this check.
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