I was wondering if anybody could explain the rationale behind disallowing
selection of individual elements from a map in CQL and why an entire map
must be retrieved at once when items are stored as distinct columns? Are
there any plans to allow individual selection?
Liam Stewart ::
Liam Stewart 's gravatar image asked Oct 28 2013 at 19:03 in Cassandra-User by Liam Stewart

2 Answers

There's some rationale here: I'm sure part of the reason is the 64k size limit: maps (and sets
and lists) are limited to 64k total size
(http://wiki.apache.org/cassandra/CassandraLimitations), so it wouldn't
be very read-efficient to load individual elements.
Keith Freeman 's gravatar image answered Oct 29 2013 at 07:24 by Keith Freeman
There is some discussion in this ticket, looks like it was pushed to a later release
https://issues.apache.org/jira/browse/CASSANDRA-3647?focusedCommentId=13292781&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13292781
I cannot find any open tickets for it https://issues.apache.org/jira/browse/CASSANDRA-5918?jql=labels%20%3D%20cql%20AND%20status%20in%20(Open%2C%20%22In%20Progress%22)
May be a good idea to create one and request the feature.
Cheers
Aaron Morton
New Zealand
@aaronmorton
Co-Founder & Principal Consultant
Apache Cassandra Consulting
http://www.thelastpickle.com
Aaron Morton 's gravatar image answered Oct 31 2013 at 01:02 by Aaron Morton