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From Doug Meil <doug.m...@explorysmedical.com>
Subject Re: Disk Seeks and Column families
Date Sat, 21 Jan 2012 18:06:43 GMT

Compression is at the block level within the StoreFile (Hfile), so yes,
they can take advantage of compression.



On 1/21/12 12:49 PM, "Praveen Sripati" <praveensripati@gmail.com> wrote:

>Thanks for the response.
>
>> The contents of a row stay together like a regular row-oriented
>>database.
>
>> K: row-550/colfam1:50/1309813948188/Put/vlen=2 V: 50
>> K: row-550/colfam1:50/1309812287166/Put/vlen=2 V: 50
>> K: row-551/colfam1:51/1309813948222/Put/vlen=2 V: 51
>> K: row-551/colfam1:51/1309812287200/Put/vlen=2 V: 51
>> K: row-552/colfam1:52/1309813948256/Put/vlen=2 V: 52
>
>Is the above statement true for a HFile?
>
>Also from the above example, the data for the column family qualifier are
>not adjacent to take advantage of compression (
>http://en.wikipedia.org/wiki/Column-oriented_DBMS#Compression). Is this a
>proper statement?
>
>Regards,
>Praveen
>
>On Sat, Jan 21, 2012 at 9:03 PM, <yuzhihong@gmail.com> wrote:
>
>> Have you considered using AggregationProtocol to perform aggregation ?
>>
>> Thanks
>>
>>
>>
>> On Jan 20, 2012, at 11:08 PM, Praveen Sripati <praveensripati@gmail.com>
>> wrote:
>>
>> > Hi,
>> >
>> > 1) According to the this url (1), HBase performs well for two or three
>> > column families. Why is it so?
>> >
>> > 2) Dump of a HFile, looks like below. The contents of a row stay
>>together
>> > like a regular row-oriented database. If the column family has 100
>>column
>> > family qualifiers and is dense then the data for a particular column
>> family
>> > qualifier is spread wide. If I want to do an aggregation on a
>>particular
>> > column identifier, the disk seeks doesn't seems to be much better
>>than a
>> > regular row-oriented database.
>> >
>> > Please correct me if I am wrong.
>> >
>> > K: row-550/colfam1:50/1309813948188/Put/vlen=2 V: 50
>> > K: row-550/colfam1:50/1309812287166/Put/vlen=2 V: 50
>> > K: row-551/colfam1:51/1309813948222/Put/vlen=2 V: 51
>> > K: row-551/colfam1:51/1309812287200/Put/vlen=2 V: 51
>> > K: row-552/colfam1:52/1309813948256/Put/vlen=2 V: 52
>> >
>> > (1) - http://hbase.apache.org/book/number.of.cfs.html
>> >
>> > Thanks,
>> > Praveen
>>



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