[jira] [Updated] (DRILL-162) Implement substring function

["Ben Becker (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DRILL-162?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ben Becker updated DRILL-162:
-----------------------------

    Attachment: substring_function.patch
    
> Implement substring function
> ----------------------------
>
>                 Key: DRILL-162
>                 URL: https://issues.apache.org/jira/browse/DRILL-162
>             Project: Apache Drill
>          Issue Type: New Feature
>            Reporter: Ben Becker
>            Assignee: Ben Becker
>         Attachments: substring_function.patch
>
>
> Implement SUBSTRING with support for byte and character (UTF-8) sequences.
> {code}
> SUBSTRING ( expression , start, length )
> {code}
> h5. Types:
> {{expression}}: VARCHAR or VARBINARY
> {{start}}: Literal BIGINT
> {{length}}: Literal BIGINT
> {{Returns}}: Same type as the {{expression}} argument
> h5. Arguments:
> {{start}}: position within the {{expression}} value the return value will start from
> {{length}}: number of subsequent characters or bytes to return.
> h5. Aliases:
> {{SUBSTR}}
> {{BYTE_SUBSTR}}
> h5. Return Value:
> Returns the specified portion of the input string.  
> h5. Notes on behavior:
>  - If the start position is negative, start from abs(start) characters from the end of the buffer.
>  - If no length is specified, continue to the end of the string.
>  - BYTE_SUBSTR always assumes a character is 8 bits, while SUBSTR accounts for UTF-8 character sequences.
>  - If the substring expression's length exceeds the value's upward bound, the
>    value's length will be used.
>  - If the substring is invalid (e.g. negative length), return an empty string.

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