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From Matthew Dennis <>
Subject Re: get keys based on values??
Date Wed, 06 Oct 2010 18:09:50 GMT
As Norman said, secondary indexes are only in .7 but you can create standard
indexes in both .6 and .7

Basically have a email_domain_idx CF where the row key is the domain and the
column names have the row id of the user (the column value is unused in this
scenario).  This sounds basically like what you described in your original
post.  That's a very common way to do it in Cassandra (C*).  This is not all
that different to what MySQL, PGSQl, etc do for you automatically, just in
C* you have to do it manually and remember to write to that index column
family whenever you write to the users CF.

On Wed, Oct 6, 2010 at 12:56 PM, Brayton Thompson <>wrote:

> Are secondary index's available in .6.5? or are they only in .7?
> On Oct 6, 2010, at 1:15 PM, Tyler Hobbs wrote:
> If you're interested in only checking part of a column's value, you can
> generally
> just store that part of the value in a different column.  So, have an
> "email_addr" column
> and a "email_domain" column, which stores "", for example.
> Then you can just use a secondary index on the "email_domain" column.
> - Tyler
> On Wed, Oct 6, 2010 at 10:33 AM, Brayton Thompson <>wrote:
>> Hash: SHA1
>> Ok, I am VERY new to Cassandra and trying to get my head around its core
>> ideas.
>> So lets say I have a CF of Users that contains all the info I would ever
>> want to know about them. One day I decide(for some reason) that I want to
>> send a mass email to only the users with AOL email addresses. Is there a
>> mechanism for getting only keys whose email attribute contains the string @
>> ? Or is this frowned upon? I could also envision separate CF's
>> for each email type; that stored values to use as keys into my Users CF. Say
>> the AOL CF contains the usernames of everyone that has an aol account. So I
>> would pull all of the keys from that CF and then use them to index into the
>> Users CF to pull their email addresses.  It seems to me that this is
>> redundant. So I would like your thoughts on my example.
>> Thank you,
>> Brayton Thompson
>> Global Research Network Operation Center
>> Indiana University
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