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https://issues.apache.org/jira/browse/HBASE-18059?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16013379#comment-16013379
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Duo Zhang commented on HBASE-18059:
-----------------------------------
Any volunteers? I'm busy with other issues right now.
The fix is trivial but I think we'd better add a UT to confirm that we do not
make this mistake again.
> 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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