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From Oleksandr Petrov <oleksandr.pet...@gmail.com>
Subject Re: Using map<varchar, varchar> type with composite primary key causes significant performance decrease
Date Thu, 18 Apr 2013 21:48:20 GMT
Write performance decreases.

Reads are basically blocked, too. Sometimes I have to wait 3-4 seconds to
get a count even though there're only couple of thousand small entries in a
table.


On Thu, Apr 18, 2013 at 8:37 PM, aaron morton <aaron@thelastpickle.com>wrote:

> After about 1-2K inserts I get significant performance decrease.
>
> A decrease in performance doing what ?
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Cassandra Consultant
> New Zealand
>
> @aaronmorton
> http://www.thelastpickle.com
>
> On 19/04/2013, at 4:43 AM, Oleksandr Petrov <oleksandr.petrov@gmail.com>
> wrote:
>
> Hi,
>
> I'm trying to persist some event data, I've tried to identify the
> bottleneck, and it seems to work like that:
>
> If I create a table with primary key based on (application, environment,
> type and emitted_at):
>
> CREATE TABLE events (application varchar, environment varchar, type
> varchar, additional_info map<varchar, varchar>, hostname varchar,
> emitted_at timestamp,
> *PRIMARY KEY (application, environment, type, emitted_at));*
>
> And insert events via CQL, prepared statements:
>
> INSERT INTO events (environment, application, hostname, emitted_at, type,
> additional_info) VALUES (?, ?, ?, ?, ?, ?);
>
> Values are: "local" "analytics" "noname" #inst "2013-04-18T16:37:02.723-00:00"
> "event_type" {"some" "value"}
>
> After about 1-2K inserts I get significant performance decrease.
>
> I've tried using only emitted_at (timestamp) as a primary key, OR writing
> additional_info data as a serialized JSON (varchar) instead of Map. Both
> scenarios seem to solve the performance degradation.
>
> I'm using Cassandra 1.2.3 from DataStax repository, running it on 2-core
> machine with 2GB Ram.
>
> What could I do wrong here? What may cause performance issues?..
> Thank you
>
>
> --
> alex p
>
>
>


-- 
alex p

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