I'm using Cassandra 1.2.7 with the official Java driver that uses CQL3.
Suppose a table created by
CREATE TABLE foo (
row int,
column int,
txt text,
PRIMARY KEY (row, column)
);
Then I'd like to preform the equivalent of SELECT DISTINCT row FROM foo
As for my understanding it should be possible to execute this query efficiently inside Cassandra's data model(given the way compound primary keys are implemented) as it would just query the 'raw' table.
I searched the CQL documentation but I didn't find any options to do that.
My backup plan is to create a separate table - something like
CREATE TABLE foo_rows (
row int,
PRIMARY KEY (row)
);
But this requires the hassle of keeping the two in sync - writing to foo_rows for any write in foo(also a performance penalty).
So is there any way to query for distinct row(partition) keys?
according to the documentation, from CQL version 3.11, cassandra understands DISTINCT modifier. So you can now write
SELECT DISTINCT row FROM foo
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