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From "Amitanand Aiyer (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5241) Deletes should not mask Puts that come after it.
Date Wed, 15 Feb 2012 20:30:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13208769#comment-13208769
] 

Amitanand Aiyer commented on HBASE-5241:
----------------------------------------

@stack. The potential performance slow down on seek is due to this:

In ScanQueryMatcher, we used to return getNextRowOrNextColumn(bytes, offset, qualLength) for
FAMILY_DELETED and COLUMN_DELETED; because once we see a KV that is deleted due to a family
or a column delete, all the remaining KV's (with a lower timestamp) are guaranteed to be deleted.

Now, we return SKIP instead. This change is required, because there might be a KV, later in
the file -- that has a lower timestamp, but a higher memstoreTS (so that deleteFamily does
not apply). In this case, we end up moving 1 KV at a time; instead of potentially skipping
the entire column or row.




                
> Deletes should not mask Puts that come after it.
> ------------------------------------------------
>
>                 Key: HBASE-5241
>                 URL: https://issues.apache.org/jira/browse/HBASE-5241
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Amitanand Aiyer
>         Attachments: HBASE-5241.D1731.1.patch
>
>
> Suppose that we have a delete row, and then followed by the put. The delete row
> can mask the put, unless there was a major compaction in between.
> Now that we are flushing the memstoreTS to disk, along with the KVs, we should be able
> to differentiate whether or not the Put happened after the Delete and offer better 
> delete semantics.
> Couldn't find a pre-existing JIRA that already discusses this, so creating one.
> Seems related to https://issues.apache.org/jira/browse/HBASE-2406, but is not quite the
same.

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