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From "Appy (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18059) The scanner order for memstore scanners are wrong
Date Tue, 16 May 2017 21:02:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18059?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16013103#comment-16013103
] 

Appy commented on HBASE-18059:
------------------------------

yes sir. It was a part of HBASE-15236.

bq. But in CompactingMemStore and DefaultMemStore, the scanner order for memstore scanner
is also start from 0, which will be messed up with StoreFileScanners.
Yes, if memstorescanners start from 0, it'll be bug.
But i see following in CompactingMemStore,
{noformat}
long order = 1 + pipelineList.size() + snapshotList.size();
{noformat}
Didn't dig around enough to make sure if it'll ensure that lowest number assigned to memstore
is more than number of store files.

> The scanner order for memstore scanners are wrong
> -------------------------------------------------
>
>                 Key: HBASE-18059
>                 URL: https://issues.apache.org/jira/browse/HBASE-18059
>             Project: HBase
>          Issue Type: Bug
>          Components: regionserver, scan, Scanners
>    Affects Versions: 2.0.0
>            Reporter: Duo Zhang
>             Fix For: 2.0.0
>
>
> This is comments for KeyValueScanner.getScannerOrder
> {code:title=KeyValueScanner.java}
>   /**
>    * Get the order of this KeyValueScanner. This is only relevant for StoreFileScanners
and
>    * MemStoreScanners (other scanners simply return 0). This is required for comparing
multiple
>    * files to find out which one has the latest data. StoreFileScanners are ordered from
0
>    * (oldest) to newest in increasing order. MemStoreScanner gets LONG.max since it always
>    * contains freshest data.
>    */
>   long getScannerOrder();
> {code}
> As now we may have multiple memstore scanners, I think the right way to select scanner
order for memstore scanner is to ordered from Long.MAX_VALUE in decreasing order.
> But in CompactingMemStore and DefaultMemStore, the scanner order for memstore scanner
is also start from 0, which will be messed up with StoreFileScanners.



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