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https://issues.apache.org/jira/browse/ACCUMULO-1801?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14026546#comment-14026546
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Josh Elser commented on ACCUMULO-1801:
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Clarifying on Russ's comment (because I had to re-read it a few times), the
case he is outlining is subject only when using the RowDeletingIterator which
is a special iterator that lazily deletes an entire row using a special
colfam+colqual marker (both cf and cq are empty). For the RowDeletingIterator
to see this marker, it also needs to be read from disk, which is where his
issue came from.
> 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: 1.7.0
>
>
> 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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