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From "An (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-625) consider augmenting session state with "breadcrumbs"
Date Mon, 14 Jan 2013 16:50:14 GMT


An commented on ACCUMULO-625:

Currently there's a UniqueColumn map/reduce example (org.apache.accumulo.examples.simple.mapreduce.UniqueColumns).
 Ideally I would like to take that example and turn it into an iterator.  Due to the tear
up and tear down factor, is it safe to assume i can only perform this operation per row bases?
So the iterator would find all the distinct column in a single row and the client would have
to perform a final distinct for all the rows?

> consider augmenting session state with "breadcrumbs"
> ----------------------------------------------------
>                 Key: ACCUMULO-625
>                 URL:
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: tserver
>            Reporter: Eric Newton
>            Assignee: Keith Turner
> Presently, the iterator stack can be created and destroyed at the whim of the tserver
and its buffering needs.  In complex iterations, lower-level iterators can make significant
progress which is not inherently obvious in any returned key.  When the iterator stack is
re-created to continue a query, the last key returned is used to {{seek()}} the iterators.
 Lower-level iterators must re-scan their data to move back to the old position.
> Consider a mechanism to save progress beyond the last key returned.

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