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From "Jonathan Gray (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4612) Allow ColumnPrefixFilter to support multiple prefixes
Date Tue, 18 Oct 2011 19:11:10 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4612?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13129955#comment-13129955
] 

Jonathan Gray commented on HBASE-4612:
--------------------------------------

Hey Eran.  Thanks for the contribution!  A few comments..

- There's no explanation of the behavior anywhere.  In the constructors and addPrefix() methods,
you should document that this creates an OR condition across all of the prefixes, correct?
- No need to instantiate a new comparator all the time (use Bytes.BYTES_COMPARATOR)
- Something seems odd when you keep adding to the end of a List and then sort.  How about
a TreeSet?  You can easily ignore dupes that way.
- There's no input verification so, for example, you could pass a null to the constructor
or an empty byte[][] and have some strange behavior.  Like it will instantiate okay but then
you'll get server-side NPEs or IOOB.
- this.prefixes.size() == 0 -> this.prefixes.isEmpty()
- your comment at the top of filterColumn, i wouldn't exactly call it a workaround, but it's
a good comment.  looking at the logic, it seems like correct behavior would be that it can
be called with current == size() but it would be a bug if current > size(), right?  should
you add an assert or throw an exception?
                
> Allow ColumnPrefixFilter to support multiple prefixes
> -----------------------------------------------------
>
>                 Key: HBASE-4612
>                 URL: https://issues.apache.org/jira/browse/HBASE-4612
>             Project: HBase
>          Issue Type: Improvement
>          Components: filters
>    Affects Versions: 0.90.4
>            Reporter: Eran Kutner
>            Priority: Minor
>         Attachments: HBASE-4612-0.90.patch
>
>
> When having a lot of columns grouped by name I've found that it would be very useful
to be able to scan them using multiple prefixes, allowing to fetch specific groups in one
scan, without fetching the entire row. This is impossible to achieve using a FilterList, so
I've added such support to the existing ColmnPrefixFilter while keeping backward compatibility.
> The attached patch is based on 0.90.4, I noticed that the 0.92 branch has a new method
to support instantiating filters using Thrift. I'm not sure how the serialization works there
so I didn't implement that, but the rest of my code should work in 0.92 as well.

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