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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4223) Support the ability to return a set of rows using Coprocessors
Date Thu, 18 Aug 2011 17:00:29 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4223?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13087111#comment-13087111

stack commented on HBASE-4223:

This patch is very interesting.  It seems to be adding new 'functionality' to coprocessors.

nit: lines lengths in the rest of the code base are generally < 80 chars and tabs are two

This is a sort of cache Nichole?

this.kvs = finalResults.toArray(new KeyValue[results.size()]);

... so you'd have to do a getList before you'd get anything out of a getMap?  Is this interdependency
doc'd anywhere?  (Similar with getNoVersionMap and dependency on getList -- isEmpty too)

I was wondering about the getMap running serverside?  Maybe just do this in client?  We're
going to have to shuttle the payload across regardless.

Yeah, paging though I'd suggest the paging be size based rather than element count.

I don't know much about how CPs work but is there means of keeping state between client and
server (with resources let go if client goes away?)

> Support the ability to return a set of rows using Coprocessors
> --------------------------------------------------------------
>                 Key: HBASE-4223
>                 URL: https://issues.apache.org/jira/browse/HBASE-4223
>             Project: HBase
>          Issue Type: Improvement
>          Components: coprocessors
>    Affects Versions: 0.92.0
>            Reporter: Nichole Treadway
>            Priority: Minor
>         Attachments: HBASE-4223.patch
> Currently HBase supports returning the results of aggregation operations using coprocessors
with the AggregationClient. It would be useful to include a client and implementation which
would return a set of rows which match a certain criteria using coprocessors as well. We have
a use case in our business process for this. 
> We have an initial implementation of this, which I've attached. The only limitation that
we've found is that it cannot be used to return very large sets of rows. If the result set
is very large, it would probably require some sort of pagination.

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