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https://issues.apache.org/jira/browse/CASSANDRA-1956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12988023#action_12988023
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Daniel Doubleday commented on CASSANDRA-1956:
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Now it's my ahh :-) I think I understood your idea.
Instead of configuring cache rules you want to cache every filtered request
like mysql query cache?
I dropped the idea because I thought it would be either very restricted to
certain query patterns or very complicated to keep in sync with memtables
and/or decide whether a query can be served by the cache. Also it might be hard
to avoid that the cache is being polluted (analogous to the page cache eviction
problem during compaction). It might force the developer to spread the data
over multiple CFs according to access pattern which increases memory needs
(more memtables, more rows).
But yes - if you can come up with an automagical cache management that just
works that would be obviously nicer!
PS: If you wan to have a look at the patch: apply to 0.7 r1064192
> Convert row cache to row+filter cache
> -------------------------------------
>
> Key: CASSANDRA-1956
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1956
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Affects Versions: 0.7.0
> Reporter: Stu Hood
> Assignee: Daniel Doubleday
> Fix For: 0.7.2
>
> Attachments: 0001-row-cache-filter.patch
>
>
> Changing the row cache to a row+filter cache would make it much more useful.
> We currently have to warn against using the row cache with wide rows, where
> the read pattern is typically a peek at the head, but this usecase would be
> perfect supported by a cache that stored only columns matching the filter.
> Possible implementations:
> * (copout) Cache a single filter per row, and leave the cache key as is
> * Cache a list of filters per row, leaving the cache key as is: this is
> likely to have some gotchas for weird usage patterns, and it requires the
> list overheard
> * Change the cache key to "rowkey+filterid": basically ideal, but you need a
> secondary index to lookup cache entries by rowkey so that you can keep them
> in sync with the memtable
> * others?
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