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Sylvain Lebresne commented on CASSANDRA-4175:
---------------------------------------------
I'm pretty sure we'd need CASSANDRA-5417 to make that doable (in fact, that's
one of my original motivation for doing CASSANDRA-5417). Namely, we don't want
a cell name/id map, we want a cql3 column/id map, otherwise this loose most
interest. And we can't do a cql3 column/id map if we store cell name as opaque
byte buffers.
To be more precise, I don't deny that a cell name/id map could be a start and
would in fact server some use cases, but I'm a bit reluctant in implementing
that knowing that we want to change to a cql3 column/id map sooner than later
because I suspect it'll be a lot easier to do "the right thing" to start with
rather than doing cell name/id map and then have a painful time to switch a
cql3 column/id one without breaking backward compatibility.
Besides, I also suspect there is a bunch of refactorings that are in
CASSANDRA-5417 that would be needed here as well, so working on both separately
without coordination is likely to be frustrating and a duplication of effort.
Anyway, I do plan on getting back to CASSANDRA-5417 asap (though it will
unlikely be like next week) so maybe we can hold a bit on that one until then?
If I've made no progress on CASSANDRA-5417 in say a month or two, and people
really want this, we can re-evaluate?
> Reduce memory, disk space, and cpu usage with a column name/id map
> ------------------------------------------------------------------
>
> Key: CASSANDRA-4175
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4175
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Jonathan Ellis
> Assignee: Jason Brown
> Fix For: 2.1
>
>
> We spend a lot of memory on column names, both transiently (during reads) and
> more permanently (in the row cache). Compression mitigates this on disk but
> not on the heap.
> The overhead is significant for typical small column values, e.g., ints.
> Even though we intern once we get to the memtable, this affects writes too
> via very high allocation rates in the young generation, hence more GC
> activity.
> Now that CQL3 provides us some guarantees that column names must be defined
> before they are inserted, we could create a map of (say) 32-bit int column
> id, to names, and use that internally right up until we return a resultset to
> the client.
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