incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Franc Carter <franc.car...@sirca.org.au>
Subject Re: sstable image/pic ?
Date Tue, 28 Feb 2012 10:01:21 GMT
2012/2/28 Hontvári József Levente <hontvari@flyordie.com>

>
>
>> * Does the column name get stored for every col/val for every key (which
>> sort of worries me for long column names)
>>
>
> Yes, the column name is stored with each value for every key, but it may
> not matter if you switch on compression, which AFAIK has only advantages
> and will be the default.  I am also worried about the storage space, so I
> did a test.
>

Yes - I'm using compression - I've seen the same outcome in one of our own
systems.


>
> There is a MySQL table which I intend to move to Cassandra. It has about
> 40 columns with very long column names, the average is 15 characters. The
> column values are mostly 2-4 byte integers. On the other hand many colums
> are empty, specifically not NULL but 0. AFAIK MySQL is also able to
> optimize NON NULL columns with 0 values to a single bit. In Cassandra I
> simply did not store a column if its value is the default 0. The table
> size, only data without indexes, in MySQL was  about 2.5 GB with 7 millions
> rows. In Cassandra it was about 12 GB without compression, and 3,4 GB with
> compression (which also includes a single index for the row keys).
>
> So with compression switched on, in this specific case the storage
> requirements are roughly the same on Cassandra and MySQL.


Good to know - thanks


>
>
>
>
>
>> * Is data in an sstable sorted by key then column or column then key
>>
>>
> Sorted by key and then sorted by column.
>
>
>
thanks

-- 

*Franc Carter* | Systems architect | Sirca Ltd
 <marc.zianideferranti@sirca.org.au>

franc.carter@sirca.org.au | www.sirca.org.au

Tel: +61 2 9236 9118

Level 9, 80 Clarence St, Sydney NSW 2000

PO Box H58, Australia Square, Sydney NSW 1215

Mime
View raw message