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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5257) Allow filter to be evaluated after version handling
Date Fri, 12 Oct 2012 05:13:03 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13474810#comment-13474810
] 

Lars Hofhansl commented on HBASE-5257:
--------------------------------------

Yep. We still need to support a single scan to specify before and after filter, though. Otherwise
there is no way to combine these in a scan.
                
> Allow filter to be evaluated after version handling
> ---------------------------------------------------
>
>                 Key: HBASE-5257
>                 URL: https://issues.apache.org/jira/browse/HBASE-5257
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Lars Hofhansl
>
> There are various usecases and filter types where evaluating the filter before version
are handled either do not make sense, or make filter handling more complicated.
> Also see this comment in ScanQueryMatcher:
> {code}
>     /**
>      * Filters should be checked before checking column trackers. If we do
>      * otherwise, as was previously being done, ColumnTracker may increment its
>      * counter for even that KV which may be discarded later on by Filter. This
>      * would lead to incorrect results in certain cases.
>      */
> {code}
> So we had Filters after the column trackers (which do the version checking), and then
moved it.
> Should be at the discretion of the Filter.
> Could either add a new method to FilterBase (maybe excludeVersions() or something). Or
have a new Filter wrapper (like WhileMatchFilter), that should only be used as outmost filter
and indicates the same (maybe ExcludeVersionsFilter).
> See latest comments on HBASE-5229 for motivation.

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