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From Shalom Sagges <shal...@liveperson.com>
Subject Re: Can a Select Count(*) Affect Writes in Cassandra?
Date Thu, 10 Nov 2016 10:47:37 GMT
Thanks for the quick reply Vladimir.
Is it really possible that ~12,500 writes per second (per node in a 12
nodes DC) are caused by memory flushes?





Shalom Sagges
DBA
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On Thu, Nov 10, 2016 at 11:02 AM, Vladimir Yudovin <vladyu@winguzone.com>
wrote:

> Hi Shalom,
>
> so not sure, but probably excessive memory consumption by this SELECT
> causes C* to flush tables to free memory.
>
> Best regards, Vladimir Yudovin,
>
> *Winguzone <https://winguzone.com?from=list> - Hosted Cloud
> CassandraLaunch your cluster in minutes.*
>
>
> ---- On Thu, 10 Nov 2016 03:36:59 -0500*Shalom Sagges
> <shaloms@liveperson.com <shaloms@liveperson.com>>* wrote ----
>
> Hi There!
>
> I'm using C* 2.0.14.
> I experienced a scenario where a "select count(*)" that ran every minute
> on a table with practically no results limit (yes, this should definitely
> be avoided), caused a huge increase in Cassandra writes to around 150
> thousand writes per second for that particular table.
>
> Can anyone explain this behavior? Why would a Select query significantly
> increase write count in Cassandra?
>
> Thanks!
>
>
> Shalom Sagges
>
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