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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Reading thousands of columns
Date Thu, 15 Apr 2010 17:46:55 GMT
How long to read just 10 columns?

On Wed, Apr 14, 2010 at 3:19 PM, James Golick <jamesgolick@gmail.com> wrote:
> The values are empty. It's 3000 UUIDs.
>
> On Wed, Apr 14, 2010 at 12:40 PM, Avinash Lakshman
> <avinash.lakshman@gmail.com> wrote:
>>
>> How large are the values? How much data on disk?
>>
>> On Wednesday, April 14, 2010, James Golick <jamesgolick@gmail.com> wrote:
>> > Just for the record, I am able to repeat this locally.
>> > I'm seeing around 150ms to read 1000 columns from a row that has 3000 in
>> > it. If I enable the rowcache, that goes down to about 90ms. According to my
>> > profile, 90% of the time is being spent waiting for cassandra to respond, so
>> > it's not thrift.
>> >
>> > On Wed, Apr 14, 2010 at 11:01 AM, Paul Prescod <prescod@gmail.com>
>> > wrote:
>> >
>> > On Wed, Apr 14, 2010 at 10:31 AM, Mike Malone <mike@simplegeo.com>
>> > wrote:
>> >> ...
>> >>
>> >> Couldn't you cache a list of keys that were returned for the key range,
>> >> then
>> >> cache individual rows separately or not at all?
>> >> By "blowing away rows queried by key" I'm guessing you mean "pushing
>> >> them
>> >> out of the LRU cache," not explicitly blowing them away? Either way I'm
>> >> not
>> >> entirely convinced. In my experience I've had pretty good success
>> >> caching
>> >> items that were pulled out via more complicated join / range type
>> >> queries.
>> >> If your system is doing lots of range quereis, and not a lot of lookups
>> >> by
>> >> key, you'd obviously see a performance win from caching the range
>> >> queries.
>> >> Maybe range scan caching could be turned on separately?
>> >
>> > I agree with you that the caches should be separate, if you're going
>> > to cache ranges. You could imagine a single query (perhaps entered
>> > interactively) would replace the entire row caching all of the data
>> > for the systems' interactive users. For example, a summary page of who
>> > is most over the last month active could replace the profile
>> > information for the actual users who are using the system at that
>> > moment.
>> >
>> >  Paul Prescod
>> >
>> >
>> >
>
>

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