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Date: Tue, 27 Jan 2015 18:55:36 +0000 (UTC)
From: "Lars Hofhansl (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
Message-ID: <JIRA.12770407.1422379565000.186695.1422384936159@Atlassian.JIRA>
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Subject: [jira] [Commented] (HBASE-12931) The existing KeyValues in memstroe
 are not removed completely after inserting cell into memStore
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    [ https://issues.apache.org/jira/browse/HBASE-12931?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14293967#comment-14293967 ] 

Lars Hofhansl commented on HBASE-12931:
---------------------------------------

I think it is the correct the way it is. We can remove all KVs *after* we have proven that the oldest scanner has seen at least one version. I.e. that scanner has to be able to see one version (versionsVisible == 1) and the following KVs can be removed (versionVisible > 1).


> The existing KeyValues in memstroe are not removed completely after inserting cell into memStore 
> -------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-12931
>                 URL: https://issues.apache.org/jira/browse/HBASE-12931
>             Project: HBase
>          Issue Type: Bug
>            Reporter: ChiaPing Tsai
>            Priority: Minor
>             Fix For: 0.98.0
>
>
> If I'm not wrong, the UPSERT method of memStore should remove all existing KeyValues except the newer version.
> In memStore,
> {code:title=DefaultMemStore.java|borderStyle=solid}
> int versIionsVisible = 0;
> ...
> if (cur.getTypeByte() == KeyValue.Type.Put.getCode() &&
>             cur.getSequenceId() <= readpoint) {
>           if (versionsVisible > 1) {
>             // if we get here we have seen at least one version visible to the oldest scanner,
>             // which means we can prove that no scanner will see this version
>             // false means there was a change, so give us the size.
>             long delta = heapSizeChange(cur, true);
>             addedSize -= delta;
>             this.size.addAndGet(-delta);
>             it.remove();
>             setOldestEditTimeToNow();
>           } else {
>             versionsVisible++;
>           }
> {code}
> Does "versionsVisible > 1" should be changed to "versionsVisible >= 1" ?
> thanks.


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