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From Robert Wille <rwi...@fold3.com>
Subject Re: OperationTimedOut in selerct count statement in cqlsh
Date Wed, 22 Apr 2015 14:09:38 GMT
And I should have read the post more clearly. I thought it was count(l), not count(1). But,
either way, you’re counting the number of records in the table, which in the RDBMS world
means scanning an index, and in Cassandra means the coordinator has to select all the records
from all the nodes.

In general, counting records in Cassandra is bad. People are accustomed to counting being
a cheap operation, but in any distributed database with replication, it is going to be expensive.
If your data model requires that you count large number of records, then I recommend you revise
your data model and maintain a counter. I know that can be a pain, but there really is not
way to count records fast.

On Apr 22, 2015, at 7:49 AM, Mich Talebzadeh <mich@peridale.co.uk<mailto:mich@peridale.co.uk>>
wrote:

Thanks Robert,

In RDBMS select count(1) basically returns the rows.

1> select count(1) from t
2> go

-----------
      300000

(1 row affected)

Is count(1) fundamentally different in Cassandra?

Does count(1) means return (in my case) 1 three hundred thousand time?

Cheers,


Mich Talebzadeh

http://talebzadehmich.wordpress.com<http://talebzadehmich.wordpress.com/>

Author of the books "A Practitioner’s Guide to Upgrading to Sybase ASE 15", ISBN 978-0-9563693-0-7.
co-author "Sybase Transact SQL Guidelines Best Practices", ISBN 978-0-9759693-0-4
Publications due shortly:
Creating in-memory Data Grid for Trading Systems with Oracle TimesTen and Coherence Cache
Oracle and Sybase, Concepts and Contrasts, ISBN: 978-0-9563693-1-4, volume one out shortly

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From: Robert Wille [mailto:rwille@fold3.com]
Sent: 22 April 2015 14:44
To: user@cassandra.apache.org<mailto:user@cassandra.apache.org>
Subject: Re: OperationTimedOut in selerct count statement in cqlsh

Keep in mind that "select count(l)" and "select l" amount to essentially the same thing.

On Apr 22, 2015, at 3:41 AM, Tommy Stendahl <tommy.stendahl@ericsson.com<mailto:tommy.stendahl@ericsson.com>>
wrote:


Hi,

Checkout CASSANDRA-8899, my guess is that you have to increase the timeout in cqlsh.

/Tommy
On 2015-04-22 11:15, Mich Talebzadeh wrote:
Hi,

I have a table of 300,000 rows.

When I try to do a simple

cqlsh:ase> select count(1) from t;
OperationTimedOut: errors={}, last_host=127.0.0.1

Appreciate any feedback

Thanks,

Mich


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of the recipient to ensure that this email is virus free, therefore neither Peridale Ltd,
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