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From aaron morton <aa...@thelastpickle.com>
Subject Re: Using WHERE IN with Wide Rows
Date Mon, 11 Mar 2013 13:20:11 GMT
What statement are you issuing ? 
What have you tried ? 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 8/03/2013, at 5:49 AM, Adam Venturella <aventurella@gmail.com> wrote:

> TL;DR:
> Is it possible to use WHERE IN on wide rows but only have it return the 1st column of
each of the rows in the IN()?
> 
> First, I am aware that WHERE IN (id1, id2, id3...N) is not the most performant, and should
not be used on large sets.
> 
> Assuming there is also little difference from just issuing N SELECTs from the requesting
application. I'm guessing Cassandra may try to perform some optimization on it's end, parallelizing
the requests to the nodes if applicable? Otherwise probably, generally speaking, it's more
or less the same-ish as issuing multiple SELECTs.
> 
> That said, I need to extract some data, and WHERE IN() is looking like the best way to
do it given that I have the row keys and just need the data. 
> 
> I have a few thousand id's and figure the best way to grab that info is in 10 id blocks
so as not to abuse WHERE IN: IN (1...10), IN(11...20). Now maybe issuing 100's of WHERE IN's
is itself being abusive; my ignorance shows though. Regardless, I still need to get some data
out =)
> 
> The next catch is the rows identified by the keys are wide rows (time series). Assuming
each row is a minimum of 100 columns wide issuing the WHERE IN seems to pull back all of the
columns for each row key specified, as expected. 
> 
> So my question. Is it possible to use WHERE IN on wide rows but only have it return the
1st column of each of the rows in the IN()?
> 
> I can also just issue SELECTs per row key as well, but I thought I would ask to see if
there was something I was missing using WHERE IN.


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