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From "Mingjie Lai (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-3583) Coprocessors: RegionObserver: ScannerNext and ScannerClose hooks are called when get() is invoked
Date Wed, 16 Mar 2011 23:44:29 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3583?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13007744#comment-13007744
] 

Mingjie Lai commented on HBASE-3583:
------------------------------------

Stack. Need your feedback for your first comments: 
https://review.cloudera.org/r/1617/diff/1/?file=26436#file26436line1812


>>>>

My original purpose of this addition map is to have a way to obtain region name from scanner
id, then get region instance, in order to call corresponding region coprocessors: 

Result[] next(final long scannerId, int nbRows) {
  // need to get to region to access coprocessors
  ... 
}

There are several options can do it:

1) add a map along with original scanners map (as the 1st patch)
2) as you suggested, to change the meaning/data type of scanner id, but it will impact other
components, ie. client lib, etc. 
3) instead of Map<InternalScanner>, just use Map<HRegion.RegionScanner> as scanners.
There are a lot of ugly thing like: 

if (scanner instanceof HRegion.RegionScanner) {
  ...
}

so why not just using HRegion.RegionScanner directly. 

4) ugly way: don't add anything, just use existing suff 

if (scanner instanceof HRegion.RegionScanner){ 
  ... 
  HRegionInfo regionName = rs.getRegionName(); ... 
}
<<<<

What do you think? 

> Coprocessors: RegionObserver: ScannerNext and ScannerClose hooks are called when get()
is invoked
> -------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-3583
>                 URL: https://issues.apache.org/jira/browse/HBASE-3583
>             Project: HBase
>          Issue Type: Bug
>          Components: coprocessors
>    Affects Versions: 0.92.0
>            Reporter: Mingjie Lai
>            Assignee: Mingjie Lai
>             Fix For: 0.92.0
>
>         Attachments: HBase3583.patch
>
>
> RegionObserver upcalls are expected to be triggered by corresponding client calls. 
> I found that if a HTable.get() is issued, ScannerNext, and ScannerClose hooks are also
invoked. 
> Here is the reason: HRegion.get() is implemented with an internal scanner:
> {code}
>     InternalScanner scanner = null;
>     try {
>       scanner = getScanner(scan);
>       scanner.next(results);
>     } finally {
>       if (scanner != null)
>         scanner.close();
>     }
> {code}
> where scanner.next, and scanner.close() are implemented with RegionObserver hooks. 

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