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From "Jonathan Ellis (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2878) Allow CQL-based map/reduce
Date Sat, 07 Jan 2012 14:54:39 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2878?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13181983#comment-13181983
] 

Jonathan Ellis commented on CASSANDRA-2878:
-------------------------------------------

bq. My understanding is implementing any of 1,2,3 won't provide support for super columns.

The only plan for supporting supercolumns for map/reduce is with something like CASSANDRA-2478.
 I say "something like it" because the syntax proposed there will allow supercolumn support,
but it's unclear at this stage whether adding that will be easy enough to do it "for free"
in the initial implementation or whether we wait until after 1.1.  My educated guess: it will
wait.  (And of course there is CASSANDRA-3237 lurking in the indefinite future as well.)

bq. We need the combination of secondary indexes and super columns

If you mean "at the same time," this isn't even on the drawing board, unless you count Jake
saying "we should support 2ary indexes for composite columns soon."  But the great thing about
this hypothetical CqlInputFormat is that if the server grows support for that in the future,
then m/r can take advantage "for free" without having to add special logic to the configuration/inputformat/recordreader
classes.
                
> Allow CQL-based map/reduce
> --------------------------
>
>                 Key: CASSANDRA-2878
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2878
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Hadoop
>            Reporter: Mck SembWever
>            Assignee: Jonathan Ellis
>            Priority: Minor
>             Fix For: 1.1
>
>
> Currently, when running a MapReduce job against data in a Cassandra data store, it reads
through all the data for a particular ColumnFamily.  This could be optimized to only read
through those rows that have to do with the query.
> Adding CQL support to m/r will allow using an index more simply than trying to cram support
for more parameters into the job configuration.

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