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From daemeon reiydelle <daeme...@gmail.com>
Subject Re: Cassandra Collections performance issue
Date Tue, 09 Feb 2016 16:39:02 GMT
I think the key to your problem might be around "we overwrite every value".
You are creating a large number of tombstones, forcing many reads to pull
current results. You would do well to rethink why you are having to to
overwrite values all the time under the same key. You would be better to
figure out haw to add values under a key then age off the old values. I
would say that (at least at scale) you have a classic anti-pattern in play.


*.......*



*Daemeon C.M. ReiydelleUSA (+1) 415.501.0198London (+44) (0) 20 8144 9872*

On Mon, Feb 8, 2016 at 5:23 PM, Robert Coli <rcoli@eventbrite.com> wrote:

> On Mon, Feb 8, 2016 at 2:10 PM, Agrawal, Pratik <paagrawa@amazon.com>
> wrote:
>
>> Recently we added one of the table fields from as Map<text, text> in *Cassandra
>> 2.1.11*. Currently we read every field from Map and overwrite map
>> values. Map is of size 3. We saw that writes are 30-40% slower while reads
>> are 70-80% slower. Please find below some metrics that can help.
>>
>> My question is, Are there any known issues in Cassandra map performance?
>> As I understand it each of the CQL3 Map entry, maps to a column in
>> cassandra, with that assumption we are just creating 3 columns right? Any
>> insight on this issue would be helpful.
>>
>
> I have previously heard reports along similar lines, but in the other
> direction.
>
> eg - "I moved from a collection to a TEXT column with JSON in it, and my
> reads and writes both became much faster!"
>
> I'm not sure if the issue has been raised as an Apache Cassandra Jira, iow
> if it is a known and expected limitation as opposed to just a performance
> issue.
>
> If I were you, I would consider filing a repro case as a Jira ticket, and
> responding to this thread with its URL. :D
>
> =Rob
>
>

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