[jira] [Created] (SPARK-32934) Support a new window frame could improve the performance for NTH_VALUE,FIRST_VALUE,LAST_VALUE

["jiaan.geng (Jira)" <ji...@apache.org>]

jiaan.geng created SPARK-32934:
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             Summary: Support a new window frame could improve the performance for NTH_VALUE,FIRST_VALUE,LAST_VALUE
                 Key: SPARK-32934
                 URL: https://issues.apache.org/jira/browse/SPARK-32934
             Project: Spark
          Issue Type: Sub-task
          Components: SQL
    Affects Versions: 3.1.0
            Reporter: jiaan.geng


Spark SQL support some window function like  NTH_VALUE,FIRST_VALUE and LAST_VALUE
If we specify window frame like


{code:java}
UNBOUNDED PRECEDING AND CURRENT ROW
{code}

or

{code:java}
UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
{code}


We can elimate some calculations.
For example: if we execute the SQL show below:

{code:java}
SELECT NTH_VALUE(col,
         2) OVER(ORDER BY rank UNBOUNDED PRECEDING
        AND CURRENT ROW)
FROM tab;
{code}
The output for row number greater than 1, return the fixed value. otherwise, return null. So we just calculate the value once and notice whether the row number less than 2.
UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING is simpler.





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