incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Robert Coli <rc...@eventbrite.com>
Subject Re: Ad-hoc queries question
Date Sat, 21 Sep 2013 00:09:55 GMT
On Fri, Sep 20, 2013 at 4:20 PM, Hartzman, Leslie <
leslie.d.hartzman@medtronic.com> wrote:

>  Thanks Rob. I thought that might have been the situation but wasn’t
> sure. So does this negate the use of cqlsh to do this then? I’d hate to
> have to provide custom code to support ad-hoc queries.
>

The form of your question is pretty vague. CQLsh, and CQL generally, give
you a bit more flexibility to construct complex queries than the old thrift
interface. The more complex these queries, however, the worse/less
predictably they are likely to perform. An example would be ALLOW
FILTERING, which the docs describe thusly.

"
By default, CQL only allows select queries that don’t involve “filtering”
server side, i.e. queries where we know that all (live) record read will be
returned (maybe partly) in the result set. The reasoning is that those “non
filtering” queries have predictable performance in the sense that they will
execute in a time that is proportional to the amount of data returned by
the query (which can be controlled through LIMIT).

The ALLOW FILTERING option allows to explicitely [sic] allow (some) queries
that require filtering. Please note that a query using ALLOW FILTERING may
thus have unpredictable performance (for the definition above), i.e. even a
query that selects a handful of records may exhibit performance that
depends on the total amount of data stored in the cluster.
"

=Rob

Mime
View raw message