cassandra-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Rick Branson (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-5527) Deletion by Secondary Key
Date Tue, 30 Apr 2013 17:20:16 GMT
Rick Branson created CASSANDRA-5527:
---------------------------------------

             Summary: Deletion by Secondary Key
                 Key: CASSANDRA-5527
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5527
             Project: Cassandra
          Issue Type: Improvement
            Reporter: Rick Branson


Given Cassandra's popularity as a time ordered list store, the inability to do deletes by
anything other than the primary key without re-implementing tombstones in the application
is a bit of an achilles heel for many use cases. It's a data modeling problem that seems to
come up quite often, and given that we now have the CQL3 abstraction layer sitting on top
of the storage engine, I think there's an opportunity to take this burden off of the application
layer. I've spent several weeks thinking about this problem within the context of Cassandra,
and I think I've come up with a reasonable proposal.

It would involve addition of a secondary key facility to CQL3 tables:

CREATE TABLE timeline (
	timeline_id uuid,
	entry_id timeuuid,
 	entry_key blob,
	entry_payload blob,
	PRIMARY KEY (timeline_id, entry_id),
	KEY (timeline_id, entry_key)
);

Secondary keys would be required to share the same partition key with the primary key. They
would be included to support deletion by secondary key operations:

DELETE FROM timeline WHERE timeline_id = <X> and entry_key = <Y>;

Underneath, the storage engine row would contain additional secondary key tombstones. Secondary
key deletion would be read-free, requiring a single tombstone write. The cost of reads would
necessarily go up. Queries would need to be modified to perform an additional step to find
any matching secondary key tombstones and perform the regular convergence process. The secondary
key tombstones should be cleaned up by the regular tombstone GC process.

While I didn't want to complicate this idea too much, it might be also worth having a discussion
around supporting secondary key queries as well, or at least making the schema compatible
with potential future support (maybe rename KEY to DELETABLE KEY or something).

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message