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https://issues.apache.org/jira/browse/DRILL-5419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16007978#comment-16007978
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ASF GitHub Bot commented on DRILL-5419:
---------------------------------------

Github user arina-ielchiieva commented on the issue:

    https://github.com/apache/drill/pull/819
  
    Squashed the commits and updated commit message to include brief 
description of the changes.


> Calculate return string length for literals & some string functions
> -------------------------------------------------------------------
>
>                 Key: DRILL-5419
>                 URL: https://issues.apache.org/jira/browse/DRILL-5419
>             Project: Apache Drill
>          Issue Type: Bug
>    Affects Versions: 1.9.0
>            Reporter: Arina Ielchiieva
>            Assignee: Arina Ielchiieva
>         Attachments: version_with_cast.JPG
>
>
> Though Drill is schema-less and cannot determine in advance what the length 
> of the column should be but if query has an explicit type/length specified, 
> Drill should return correct column length.
> For example, JDBC / ODBC Driver is ALWAYS returning 64K as the length of a 
> varchar or char even if casts are applied.
> Changes:
> *LITERALS*
> String literals length is the same as actual literal length.
> Example: for 'aaa' return length is 3.
> *CAST*
> Return length is the one indicated in cast expression. This also applies when 
> user has created view where each string columns was casted to varchar with 
> some specific length.
> This length will be returned to the user without need to apply cast one more 
> time. Below mentioned functions can take leverage of underlying varchar 
> length and calculate return length.
> *LOWER, UPPER, INITCAP, REVERSE, FIRST_VALUE, LAST_VALUE* 
> Return length is underlying column length, i.e. if column is known, the same 
> length will be returned.
> Example:
> lower(cast(col as varchar(30))) will return 30.
> lower(col) will return max varchar length, since we don't know actual column 
> length.
> *LAG, LEAD*
> Return length is underlying column length but column type will be nullable.
> *LPAD, RPAD*
> Pads the string to the length specified. Return length is this specified 
> length. 
> *CONCAT, CONCAT OPERATOR (||)*
> Return length is sum of underlying columns length. If length is greater then 
> varchar max length,  varchar max length is returned.
> *IF EXPRESSIONS (CASE STATEMENT, COALESCE), UNION OPERATOR*
> When combining string columns with different length, return length is max 
> from source columns.



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