[jira] [Updated] (DRILL-346) Runtime generated code should evaluate constant expression once in doSetup method

["Jinfeng Ni (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DRILL-346?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jinfeng Ni updated DRILL-346:
-----------------------------

    Attachment:     (was: DRILL_346.1.patch.txt)

> Runtime generated code should evaluate constant expression once in doSetup method
> ---------------------------------------------------------------------------------
>
>                 Key: DRILL-346
>                 URL: https://issues.apache.org/jira/browse/DRILL-346
>             Project: Apache Drill
>          Issue Type: Bug
>            Reporter: Jinfeng Ni
>            Assignee: Jinfeng Ni
>         Attachments: DRILL_346.2.patch.txt
>
>
> Currently, when runtime CodeGenerator logic generates class to evaluate an expression, it would put the code in doEval() method, regardless of whether the expression is a constant, or part of the expression is a constant. This means the generated code for the constant expression will be executed once for every record, in stead of once for each record batch. 
> For a constant expression, we should put the code in doSetup() method, so that it will be executed once per record batch. Doing so would improve runtime code efficiency. 
> In addition,  for some function call expression, if the arguments are constant, we may want to refer to the constant arguments in doSetup(). For instance, given function : regexp_replae(input_string, regex, replace), if regex is a constant (eg : regexp_replace(varcharcol, "a[bc]", "XYZ") ), the implementation of regexp_replace would use the constant to build a java.Pattern in doSetup(),  and repeatedly use that java.Pattern object in doEval() for each record. This requires CodeGenerator to make the constant arguments accessible to doSetup() method for function call. 
>   



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