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From Minh Duc Nguyen <mdngu...@gmail.com>
Subject Re: In memory table after using 'alter'
Date Thu, 28 Jun 2012 14:35:45 GMT
Sever, I'd say that the wiki page is incomplete when discussing bloom
filters.  The HBase Reference Guide

http://hbase.apache.org/book.html#schema.bloom

provides a much better explanation of the different bloom filter options.

   ~ Minh

On Thu, Jun 28, 2012 at 9:54 AM, Sever Fundatureanu
<fundatureanu.sever@gmail.com> wrote:
> Thanks, Minh.
> This blog also mentions that bloom filters check "if a given column exists
> in a given row". However in "HBase: The definitive guide" it is mentioned
> that "enabling the Bloom filter does give you the immediate advantage of
> knowing if a file contains a particular row key or not". Is the blog post a
> bit outdated?
>
> Thanks,
> Sever
>
>
> On Wed, Jun 27, 2012 at 6:00 PM, Minh Duc Nguyen <mdnguyen@gmail.com> wrote:
>
>> Sever, the IN_MEMORY option doesn't change when table content is
>> transferred into RAM.  Whether set to true or false, the blocks of
>> data are only loaded into memory after a normal retrieval operation.
>> When IN_MEMORY is set to true, HBase just tries to keep data in memory
>> more aggressively than it normally would.  This wiki explains it in
>> more detail:
>>
>>
>> http://jimbojw.com/wiki/index.php?title=Understanding_HBase_column-family_performance_options
>>
>>   ~ Minh
>>
>> On Wed, Jun 27, 2012 at 7:18 AM, Sever Fundatureanu
>> <fundatureanu.sever@gmail.com> wrote:
>> > Hello,
>> >
>> > I initially created a table without the IN_MEMORY option enabled and
>> loaded
>> > some data into it. Then I disabled it, modified the IN_MEMORY option
>> using
>> > the hbase shell 'alter' command, re-enabled it and finally ran a major
>> > compaction. I do notice now the memory usage of the region servers has
>> > increased. However for some queries I am still getting faster responses
>> > only the 2nd time, as if I'm hitting the cache. Can someone tell me when
>> > does the table content get transferred into RAM if IN_MEMORY option is
>> > enabled like above?
>> >
>> > Thank you,
>> > --
>> > Sever Fundatureanu
>> >
>> > Vrije Universiteit Amsterdam
>> > E-mail: fundatureanu.sever@gmail.com
>>
>
>
>
> --
> Sever Fundatureanu
>
> Vrije Universiteit Amsterdam
> Tel: +31644329534
> E-mail: fundatureanu.sever@gmail.com

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