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https://issues.apache.org/jira/browse/CASSANDRA-1956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13180912#comment-13180912
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Jonathan Ellis commented on CASSANDRA-1956:
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bq. It seems to me that what we want to handle here is exactly the 'cache head
or tail of row' problem.
That, and "I want to cache a specific set of known-ahead-of-time columns [maybe
the entire row]," which is what today's row cache is mostly used for.
I think it's a huge, huge win for a design to be able to handle both of these,
*without* requiring it to be specified in the schema. We've been moving away
from hand-tuning, towards self-tuning, for a very good reason: when you require
humans to do the right thing to be efficient, you're going to be inefficient an
awful lot of the time. :)
> 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
> Reporter: Stu Hood
> Assignee: Vijay
> Priority: Minor
> Fix For: 1.2
>
> Attachments: 0001-1956-cache-updates-v0.patch,
> 0001-re-factor-row-cache.patch, 0001-row-cache-filter.patch,
> 0002-1956-updates-to-thrift-and-avro-v0.patch, 0002-add-query-cache.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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