Cassandra makes no attempt to provide cross-row isolation or atomicity.
(Within a row, it technically provides atomicity but not isolation.)
On Fri, Sep 9, 2011 at 9:33 PM, wrote:
> I a thinking about a scenario that goes like this: a node is reading a
> secondary index to reply to a select que
I a thinking about a scenario that goes like this: a node is reading a
secondary index to reply to a select query. While in the middle of this,
two rows are mutated, one that has already been read and considered for
the select result, and one that is yet to be processed. Say both rows
where changed
Consider this scenario in a SQL database:
UPDATE foo SET x = 1 WHERE key = 'asdf';
Now, "simultaneously," two clients run
UPDATE foo SET x = 2 WHERE key = 'asdf';
and
SELECT * FROM foo WHERE x = 1;
Either you get back row asdf, or you don't. Either is valid. Same
thing happens with Cassandra
I see that Cassandra updates secondary indices as soon as a value of the
indexed column is updated. This can happen, for example, during a select
query with a condition on a secondary index. Does Cassandra perform no
checking or locking? Will the result of this select, with old and new
values, be r
