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_r403515624
########## 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 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 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[AbstractDataType] = 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.") + } + length += 1 + // skip all the child of inner object or array + parser.skipChildren() Review comment: Yes. Actually Jackson parser will throw JsonProcessingException in case of invalid JSON. So, it is not required to check here. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org