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From "William Slacum (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-625) consider augmenting session state with "breadcrumbs"
Date Mon, 14 Jan 2013 17:34:12 GMT


William Slacum commented on ACCUMULO-625:

You are correct that you can only safely assume that your iterator function will only apply
to a single row. It is actually on a tablet, but that's a transient thing because it can contain
one to many rows.

In regards to unique columns, preserving session state would not allow you to wrap all of
that functionality in an iterator. You'll have an iterator stack running on multiple tservers
that are unable to communicate with each other. There will always have to be some client work
going on to merge the results.
> 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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