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From "Khurram Faraaz (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-5099) support OFFSET values greater than one, for LEAD & LAG window functions
Date Sat, 03 Dec 2016 18:41:59 GMT
Khurram Faraaz created DRILL-5099:
-------------------------------------

             Summary: support OFFSET values greater than one, for LEAD & LAG window functions
                 Key: DRILL-5099
                 URL: https://issues.apache.org/jira/browse/DRILL-5099
             Project: Apache Drill
          Issue Type: Bug
          Components: Execution - Flow
    Affects Versions: 1.9.0
            Reporter: Khurram Faraaz
            Priority: Minor


Provide support for OFFSET values greater than one, for LEAD & LAG window functions.

Adding [~adeneche] comments from the dev list here

{noformat}
Things that need to be done to make Lag (or Lead) support offsets other
than 1:
- WindowFunction.Lead should extract the offset value from its FunctionCall
argument, you can look at WindowFunctionNtile.numTilesFromExpression() for
and example on how to do that.
- make sure calls to copyNext() and copyPrev() in NoFrameSupportTemplate
use the offset and not the hard coded value (you already figured that out)
- finally make sure you update UnsupportedOperatorsVisitor to no longer
throw an exception when we pass an offset value other than 1 to Lead or
Lag. Just search for DRILL-3596 in that class and you will find the if
block that need to be removed

I think this should be enough to get it to work in the general case.
{noformat}



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