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From "Mike Drob (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1801) Create a SelectColumnsIterator
Date Tue, 22 Oct 2013 16:17:42 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1801?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13801964#comment-13801964
] 

Mike Drob commented on ACCUMULO-1801:
-------------------------------------

[~bills], that is exactly the use case that I had in mind, but the only iterator that I saw
that I could use as a column family filter was the regex one, and that didn't seem quite palatable.
It's very possible that an iterator already exists to do what I want, and I simply missed
it.

> Create a SelectColumnsIterator
> ------------------------------
>
>                 Key: ACCUMULO-1801
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-1801
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client
>            Reporter: Mike Drob
>            Priority: Minor
>             Fix For: 1.5.1, 1.6.0
>
>
> A user can already limit columns on a scanner, however there is not an easy way to limit
the columns propagated in the middle of an iterator stack. For example, if a user has data
like the following:
> {noformat}
> user-1 age:25
> user-1 occupation:Student
> user-2 age:45
> user-2 occupation:Engineer
> {noformat}
> and wants to get only the users that are younger than 30, it is easy to write a custom
{{RowFilter}} to do that.
> However, to get only the occupation of users under 30, there would need to be additional
filtering done on the client side. If the rows get large or particularly numerous, then this
becomes undesirable. And setting the fetch columns is not an option since that would hide
the age column from the {{RowFilter}}.



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