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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5664) CP hooks in Scan flow for fast forward when filter filters out a row
Date Fri, 28 Sep 2012 15:01:09 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5664?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13465651#comment-13465651
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ramkrishna.s.vasudevan commented on HBASE-5664:
-----------------------------------------------

@Lars
Anoop has clearly mentioned the scenario.  When i commented about this in HBASE-6577 i did
not mention the usecase where we are trying to add such hooks.
Here we are ideally not doing the forwarding that is done by the Scans, whereas it is something
we leave it to the CP to decide on what to reseek rather than we reseeking on the kernel like
in HBASE-6577. This hook is really useful for us.
                
> CP hooks in Scan flow for fast forward when filter filters out a row
> --------------------------------------------------------------------
>
>                 Key: HBASE-5664
>                 URL: https://issues.apache.org/jira/browse/HBASE-5664
>             Project: HBase
>          Issue Type: Improvement
>          Components: Coprocessors
>    Affects Versions: 0.92.1
>            Reporter: Anoop Sam John
>            Assignee: Anoop Sam John
>             Fix For: 0.96.0
>
>
> In HRegion.nextInternal(int limit, String metric)
> 	We have while(true) loop so as to fetch a next result which satisfies filter condition.
When Filter filters out the current fetched row we call nextRow(byte [] currentRow) before
going with the next row.
> {code}	
> if (results.isEmpty() || filterRow()) {
>             // this seems like a redundant step - we already consumed the row
>             // there're no left overs.
>             // the reasons for calling this method are:
>             // 1. reset the filters.
>             // 2. provide a hook to fast forward the row (used by subclasses)
>             nextRow(currentRow);
> {code}
> // 2. provide a hook to fast forward the row (used by subclasses)
> We can provide same feature of fast forward support for the CP also.

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