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From "Dave Brosius" <dbros...@mebigfatguy.com>
Subject Re: Column Family per User
Date Wed, 18 Apr 2012 20:58:41 GMT
Yes in this cassandra model, time wouldn't be a column value, it would be part of the column
name. Depending on how you want to access your data (give me all data points for time X) and
how many separate datapoints you have for time X, you might consider packing all the data
for a time in one column thru composite columnscolumn name: 2012-04-12T12:22:23.293/55/45/10
(where / is a human readable representation of the composite separator) in this case there
wouldn't actually be a value, the data is just encoded in the column name.Obviously if you
are storing dozens of separate datapoints for a timestamp than this gets out of hand quickly,
and perhaps you need to go back to column names with time/fieldname format with a real value.the
advantage tho of the composite key is that you eliminate all that constant blather about 'Wind'
'Rain' 'Sunshine' in your data and only hold real data. (granted compression will probably
help here, but not having it all is even better).as for row size, obv
 iously that takes some experimentation on you part. You can bucket a row to be any time frame
you want. If you feel that 15 minutes is the correct length of time given the amount of data
you will write, then use 15 minutes. It it's 1 hour, use 1 hour. The only thing you have to
figure out is a 'bucket time' definition that you understand, likely it's the timestamp of
when that time period starts.As for 'rotating the row', perhaps it's just semantics, but there
really is no such concept. You are at some point in time, and you want to write some data
to the database.The steps are1) get the user2) get the timestamp of the current bucket based
on 'now'3) build a composite key4) insert the data with that keyWhether that row existed before
or is a new row has no bearing on your client code.  ----- Original Message -----From: &quot;Trevor
Francis&quot; >;trevor.francis@tgrahamcapital.com 
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