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From Nate McCall <>
Subject Re: Performance problem with large wide row inserts using CQL
Date Wed, 19 Feb 2014 15:27:03 GMT
Hi Rüdiger,
I just saw this after I answered on the SO thread:

On Wed, Feb 19, 2014 at 8:57 AM, John Sanda <> wrote:

> From a quick glance at your code, it looks like you are preparing your
> insert statement multiple times. You only need to prepare it once. I would
> expect to see some improvement with that change.
> On Wed, Feb 19, 2014 at 5:27 AM, Rüdiger Klaehn <> wrote:
>> Hi all,
>> I am evaluating Cassandra for satellite telemetry storage and analysis. I
>> set up a little three node cluster on my local development machine and
>> wrote a few simple test programs.
>>  My use case requires storing incoming telemetry updates in the database
>> at the same rate as they are coming in. A telemetry update is a map of
>> name/value pairs that arrives at a certain time.
>> The idea is that I want to store the data as quickly as possible, and
>> then later store it in an additional format that is more amenable to
>> analysis.
>> The format I have chosen for my test is the following:
>>   time varchar,
>>   name varchar,
>>   value varchar,
>>   PRIMARY KEY (time,name))
>> The layout I want to achieve with this is something like this:
>> +-------+-------+-------+-------+-------+-------+
>> |       | name1 | name2 | name3 | ...   | nameN |
>> | time  +-------+-------+-------+-------+-------+
>> |       | val1  | val2  | val3  | ...   | valN  |
>> +-------+-------+-------+-------|-------+-------+
>> (Time will at some point be some kind of timestamp, and value will become
>> a blob. But this is just for initial testing)
>> The problem is the following: I am getting very low performance for bulk
>> inserts into the above table. In my test program, each insert has a new,
>> unique time and creates a row with 10000 name/value pairs. This should map
>> into creating a new row in the underlying storage engine, correct? I do
>> that 1000 times and measure both time per insert and total time.
>> I am getting about 0.5s for each insert of 10000 name/value pairs, which
>> is much lower than the rate at which the telemetry is coming in at my
>> system. I have read a few previous threads on this subject and am using
>> batch prepared statements for maximum performance (
>> ). But that does
>> not help.
>> Here is the CQL benchmark:
>> I have written the exact same thing using the thrift API of astyanax, and
>> I am getting much better performance. Each insert of 10000 name/values
>> takes 0.04s using a ColumnListMutation. When I use async calls for both
>> programs, as suggested by somebody on Stackoverflow, the difference gets
>> even larger. The CQL insert remains at 0.5s per insert on average, whereas
>> the astyanax ColumnListMutation approach takes 0.01s per insert on
>> average, even on my test cluster. That's the kind of performance I need.
>> Here is the thrift benchmark, modified from an ast example:
>> I realize that running on a test cluster on localhost is not a 100%
>> realistic test. But nevertheless you would expect both tests to have
>> roughly similar performance.
>> I saw a few suggestions to create a table with CQL and fill it using the
>> thrift API. For example in this thread
But I would very much prefer to use pure CQL for this. It seems that the
>> thrift API is considered deprecated, so I would not feel comfortable
>> starting a new project using a legacy API.
>> I already posted a question on SO about this, but did not get any
>> satisfactory answer. Just general performance tuning tips that do nothing
>> to explain the difference between the CQL and thrift approaches.
>> Am I doing something wrong, or is this a fundamental limitation of CQL.
>> If the latter is the case, what's the plan to mitigate the issue?
>> There is a JIRA issue about this (
>> ), but it is marked
>> as a duplicate of .
>> But according to my benchmarks batch prepared statements do not solve this
>> issue!
>> I would really appreciate any help on this issue. The telemetry data I
>> would like to import into C* for testing contains ~2*10^12 samples, where
>> each sample consists of time, value and status. If quick batch insertion is
>> not possible, I would not even be able to insert it in an acceptable time.
>> best regards,
>> Rüdiger
> --
> - John

Nate McCall
Austin, TX

Co-Founder & Sr. Technical Consultant
Apache Cassandra Consulting

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