spark目前已經内置的函數參見:
<a href="https://databricks.com/blog/2015/09/16/spark-1-5-dataframe-api-highlights-datetimestring-handling-time-intervals-and-udafs.html" target="_blank">spark 1.5 dataframe api highlights: date/time/string handling, time intervals, and udafs</a>
如果在spark函數中使用udf或udaf, 詳見示例