PySpark DataFrame - rank() and dense_rank() Functions

Code description

In Spark SQL, rank and dense_rank functions can be used to rank the rows within a window partition. In Spark SQL, we can use RANK(Spark SQL - RANK Window Function) and DENSE_RANK(Spark SQL - DENSE_RANK Window Function). This code snippet implements ranking directly using PySpark DataFrame APIs instead of Spark SQL. It created a window that partitions the data by TXN_DT attribute and sorts the records in each partition via AMT column in descending order. The frame boundary of the window is defined as unbounded preceding and current row. 

Output:

    +----+------+-------------------+----+----------+
    |ACCT|   AMT|             TXN_DT|rank|dense_rank|
    +----+------+-------------------+----+----------+
    | 101|102.01|2021-01-01 00:00:00|   1|         1|
    | 102|  93.0|2021-01-01 00:00:00|   2|         2|
    | 101| 10.01|2021-01-01 00:00:00|   3|         3|
    | 103| 913.1|2021-01-02 00:00:00|   1|         1|
    | 101|900.56|2021-01-03 00:00:00|   1|         1|
    | 102|900.56|2021-01-03 00:00:00|   1|         1|
    | 103|  80.0|2021-01-03 00:00:00|   3|         2|
    +----+------+-------------------+----+----------+

As printed out, the difference between dense_rank and rank is that the former will not generate any gaps if the ranked values are the same for multiple rows. 

Code snippet

    from pyspark.sql import SparkSession, Window
    from datetime import datetime
    from pyspark.sql.functions import rank, dense_rank, desc
    
    app_name = "PySpark rank and dense_rank Window Function"
    master = "local"
    
    spark = SparkSession.builder         .appName(app_name)         .master(master)         .getOrCreate()
    
    spark.sparkContext.setLogLevel("WARN")
    
    data = [
        [101, 10.01, datetime.strptime('2021-01-01', '%Y-%m-%d')],
        [101, 102.01, datetime.strptime('2021-01-01', '%Y-%m-%d')],
        [102, 93.0, datetime.strptime('2021-01-01', '%Y-%m-%d')],
        [103, 913.1, datetime.strptime('2021-01-02', '%Y-%m-%d')],
        [101, 900.56, datetime.strptime('2021-01-03', '%Y-%m-%d')],
        [102, 900.56, datetime.strptime('2021-01-03', '%Y-%m-%d')],
        [103, 80.0, datetime.strptime('2021-01-03', '%Y-%m-%d')]
    ]
    
    df = spark.createDataFrame(data, ['ACCT', 'AMT', 'TXN_DT'])
    df.show()
    
    window = Window.partitionBy('TXN_DT').orderBy(desc("AMT")).rowsBetween(
        Window.unboundedPreceding, Window.currentRow)
    df = df.withColumn('rank', rank().over(window)).withColumn(
        'dense_rank', dense_rank().over(window))
    
    df.show()