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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2474) CQL support for compound columns
Date Fri, 10 Jun 2011 15:24:59 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2474?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13047241#comment-13047241
] 

Jonathan Ellis commented on CASSANDRA-2474:
-------------------------------------------

bq. How about a nested SELECT

That's an interesting idea.

I work best with examples.  So let's take my proposal

{noformat}
SELECT x, y FROM foo:bar WHERE parent='columnA'
{noformat}

and try to come up with a nested-select equivalent.  IMO the most natural would be

{noformat}
SELECT x, y
FROM (SELECT * from foo where id='bar')
WHERE parent='columnA'
{noformat}

My problem with this is that the semantics are completely different than what I would expect
from a relational system, and there is no cue telling me to expect that difference other than
if I happen to know "nested-selects magically trigger transpose."  As someone with a fairly
long relational background this would drive me crazy. :)

More practically, I'd like to provide a single syntax for compound columns in both CQL and
HQL (Hive's SQL) on Cassandra.  HQL _does_ support "real" nested selects so trying to figure
out when a nested select should transpose vs when it should not seems like a non-starter to
me.

> CQL support for compound columns
> --------------------------------
>
>                 Key: CASSANDRA-2474
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2474
>             Project: Cassandra
>          Issue Type: Sub-task
>          Components: API, Core
>            Reporter: Eric Evans
>              Labels: cql
>             Fix For: 1.0
>
>
> For the most part, this boils down to supporting the specification of compound column
names (the CQL syntax is colon-delimted terms), and then teaching the decoders (drivers) to
create structures from the results.

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