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Jonathan Ellis commented on CASSANDRA-2878:
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bq. i do have a upcoming usecase where a basic combination would be useful: m/r
over all rows where a given supercolumn exists. Is this possible? Can you point
me towards relevant issues?
Not really. Even on non-supercolumns we don't have "existence" indexes. You
can kind of workaround it (in the non-SC case) by setting a "flag" column to
stand in for that, though. In the SC case I wonder if you could put the
relevant data in a separate CF.
> 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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