incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Peter Lin <wool...@gmail.com>
Subject Re: Ad-hoc queries question
Date Fri, 20 Sep 2013 23:30:29 GMT
What do you mean by ad-hoc queries?

Most NoSql databases do not support cross table joins, due to the
distributed nature of NoSql databases. If we compare this to partitioned
databases in the RDB world, cross partition joins is also more expensive
than non-partitioned databases.

you can do ad-hoc queries on a single table as long as the columns have
secondary indexes defined. You can do multi-table joins using MapReduce or
using CQL handle that logic in your application. In some cases, you can use
the concept of summary tables to speed up complex multi-table adhoc queries
that have nasty joins. One thing that is very hard to do with all NoSql
databases is complex correlated subqueries. For those kinds of use cases,
MapReduce is the "preferred" technique.

for comparison, databases like Oracle RAC distribute table indexes and
perform index joins to speed up complex multi-table joins. The downside is
a full Oracle RAC is very expensive and has a high up front cost.


On Fri, Sep 20, 2013 at 7:20 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.****
>
> ** **
>
> Les****
>
> ** **
>
> *From:* Robert Coli [mailto:rcoli@eventbrite.com]
> *Sent:* Friday, September 20, 2013 4:06 PM
> *To:* user@cassandra.apache.org
> *Subject:* Re: Ad-hoc queries question****
>
> ** **
>
> On Fri, Sep 20, 2013 at 3:25 PM, Hartzman, Leslie <
> leslie.d.hartzman@medtronic.com> wrote:****
>
>  So are ad-hoc queries more awkward or not feasible?****
>
>  ** **
>
> Yes.****
>
> ** **
>
> To expand slightly, you will probably end up querying multiple
> columnfamilies and doing the ad-hoc JOIN-esque aspect in application code.
> ****
>
> ** **
>
> =Rob****
>
> ** **
>
> [CONFIDENTIALITY AND PRIVACY NOTICE] Information transmitted by this email
> is proprietary to Medtronic and is intended for use only by the individual
> or entity to which it is addressed, and may contain information that is
> private, privileged, confidential or exempt from disclosure under
> applicable law. If you are not the intended recipient or it appears that
> this mail has been forwarded to you without proper authority, you are
> notified that any use or dissemination of this information in any manner is
> strictly prohibited. In such cases, please delete this mail from your
> records. To view this notice in other languages you can either select the
> following link or manually copy and paste the link into the address bar of
> a web browser: http://emaildisclaimer.medtronic.com
>

Mime
View raw message