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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5980) Scanner responses from RS should include metrics on rows/KVs filtered
Date Thu, 10 May 2012 04:20:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13272073#comment-13272073
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Todd Lipcon commented on HBASE-5980:
------------------------------------

Yep - some proxy for the efficiency of the filter. Often, newer HBase users apply filters
expecting them to work like SQL WHERE clauses, and don't realize that even though their scan
returns only 100 rows, it in fact is reading thousands or millions off disk.
                
> Scanner responses from RS should include metrics on rows/KVs filtered
> ---------------------------------------------------------------------
>
>                 Key: HBASE-5980
>                 URL: https://issues.apache.org/jira/browse/HBASE-5980
>             Project: HBase
>          Issue Type: Improvement
>          Components: client, metrics, regionserver
>    Affects Versions: 0.96.0
>            Reporter: Todd Lipcon
>            Priority: Minor
>
> Currently it's difficult to know, when issuing a filter, what percentage of rows were
skipped by that filter. We should expose some basic counters back to the client scanner object.
For example:
> - number of rows filtered by row key alone (filterRowKey())
> - number of times each filter response was returned by filterKeyValue() - corresponding
to Filter.ReturnCode
> What would be slickest is if this could actually return a tree of counters for cases
where FilterList or other combining filters are used. But a top-level is a good start.

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