Mailing-List: contact user-help@cassandra.apache.org; run by ezmlm
Precedence: bulk
Reply-To: user@cassandra.apache.org
Received-SPF: pass (nike.apache.org: local policy)
DomainKey-Signature: a=rsa-sha1; c=nofws; d=thelastpickle.com; h=content-type
	:mime-version:subject:from:in-reply-to:date
	:content-transfer-encoding:message-id:references:to; q=dns; s=
	thelastpickle.com; b=cPwU0GauwgfFKJksGL1zYM9Np56UG2QpdmhfQBUT8ZV
	M28XP8yV7NUtMImLCYo4vg2tB1STtR5aR8d0PcBroJZBOMzOaGc5/yqodLdNoiNh
	HIAzD62PByE+edVuNM3JqzLBRbWOUAvAj2yRk54sAteqAWnK9/+a73uqivhJZqTs
	=
Content-Type: text/plain; charset=us-ascii
Mime-Version: 1.0 (Apple Message framework v1084)
Subject: Re: hadoop results
From: aaron morton <aaron@thelastpickle.com>
In-Reply-To: <BANLkTi=4L24nGjaOG6X842Biu1m8zfo7+A@mail.gmail.com>
Date: Thu, 30 Jun 2011 15:16:09 +1200
Content-Transfer-Encoding: quoted-printable
Message-Id: <B849EF6F-ECF1-450D-B6C6-60367E0B7151@thelastpickle.com>
References: <BANLkTi=4L24nGjaOG6X842Biu1m8zfo7+A@mail.gmail.com>
To: user@cassandra.apache.org

How about  get_slice() with reversed =3D=3D true and count =3D 1 to get =
the highest time UUID ?=20

Or you can also store a column with a magic name that have the value of =
the timeuuid that is the current metric to use.=20

Cheers

-----------------
Aaron Morton
Freelance Cassandra Developer
@aaronmorton
http://www.thelastpickle.com

On 30 Jun 2011, at 06:35, William Oberman wrote:

> I'll start with my question: given a CF with comparator TimeUUIDType, =
what is the most efficient way to get the greatest column's value?
>=20
> Context: I've been running cassandra for a couple of months now, so =
obviously it's time to start layering more on top :-)  In my test =
environment, I managed to get pig/hadoop running, and developed a few =
scripts to collect metrics I've been missing since I switched from MySQL =
to cassandra (including the ever useful "select count(*) from table" =
equivalent). =20
>=20
> I was hoping to dump the results of this processing back into =
cassandra for use in other tools/processes.  My initial thought was: new =
CF called "stats" with comparator TimeUUIDType.  The basic idea being =
I'd store:
> stat_name -> time stat was computed (as UUID) -> value
> That way I can also see a historical perspective of any given stat for =
auditing (and for cumulative stats to see trends).  The stat_name itself =
is a URI that is composed of "what" and any constraints on the "what" =
(including an optional time range, if the stat supports it).  E.g. =
ClassOfSomething/ID/MetricName/OptionalTimeRange (or something, still =
deciding on the format of the URI).  But, right now, the only way I know =
to get the "current" stat value would be to iterate over all columns =
(the TimeUUIDs) and then return the last one.
>=20
> Thanks for any tips,
>=20
> will