Github user HyukjinKwon commented on a diff in the pull request: https://github.com/apache/spark/pull/20400#discussion_r164968965 --- Diff: python/pyspark/sql/functions.py --- @@ -809,6 +809,45 @@ def ntile(n): return Column(sc._jvm.functions.ntile(int(n))) +@since(2.3) +def unboundedPreceding(): + """ + Window function: returns the special frame boundary that represents the first row + in the window partition. + >>> df = spark.createDataFrame([(5,)]) + >>> df.select(unboundedPreceding()).show + <bound method DataFrame.show of DataFrame[UNBOUNDED PRECEDING: null]> --- End diff -- I think we should have a working example here in doc tests here.
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