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Sylvain Lebresne commented on CASSANDRA-5357:
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bq. Personally I'd lean towards (2)
Personally, I'd lean towards both :). That is, I'd add a new
rows_per_partition_to_cache table option that would either be a user set fixed
value, or some auto (the default presumably) that we would determine
automatically. Of course, in the interest of shipping sooner, the auto option
could be added later on. But while I'm all for having smart automatic default
options that most user don't have to ever change, it seems to me that for
something as important as caching, there will always be cases where the user
will know better than whatever heuristic we come up.
bq. I think this also means we should go back to a separate cache per CF with
its own size limit – if we have 1000 queries/s against CF X's cache, then we
shouldn't throw those away when a query against CF Y comes in where we expect
only 10/s
It seems to me that this reasoning apply equally well to the current row cache.
Is there something specific to this ticket that makes you say that, or is it
just saying "making the caches global was possibly a mistake we'd want to
reconsider"? For what is worth, when we made the caches global, that kind of
objection was raised and the answer had been that you could disable caching for
CF Y to avoid that and that if that was not enough we'd add optional per-CF
quota on top of the global one later on. Overall, I do think we really should
maintain a global limit on how much is cached, though I don't disagree that
some finer per-CF quotas could be desirable.
> Query cache / partition head cache
> ----------------------------------
>
> Key: CASSANDRA-5357
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5357
> Project: Cassandra
> Issue Type: New Feature
> Reporter: Jonathan Ellis
> Assignee: Marcus Eriksson
> Fix For: 2.1
>
>
> I think that most people expect the row cache to act like a query cache,
> because that's a reasonable model. Caching the entire partition is, in
> retrospect, not really reasonable, so it's not surprising that it catches
> people off guard, especially given the confusion we've inflicted on ourselves
> as to what a "row" constitutes.
> I propose replacing it with a true query cache.
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