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From "Brian Loss (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-956) Iterator to transform key parts
Date Fri, 11 Jan 2013 17:36:12 GMT


Brian Loss commented on ACCUMULO-956:

I not sure there is a problem.  The KeyTransformingIterator transforms only single keys, so
you can't do any aggregation.  If you had some kind of aggregating iterator on top of it on
the stack, it would need to read enough keys from its source to do the aggregation.  To produce
your example, I think you'd have to scan all the cf: keys from the source to know it has what
it needs for r cf: even [v2, v4].  Since that iterator would be scanning its source, there
is no problem with the stack getting torn down and re-seeked.  Or am I missing something?
> Iterator to transform key parts
> -------------------------------
>                 Key: ACCUMULO-956
>                 URL:
>             Project: Accumulo
>          Issue Type: Improvement
>            Reporter: Brian Loss
>             Fix For: 1.5.0
>         Attachments: key_transforming_iterator.patch
> Iterators that transform parts of the key can be tricky if any transformation affects
sort ordering.  Implement an iterator that takes care of the tricky details that come with
modifying sort order (e.g., handling scan-time iterator reconstruction and the associated

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