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From "Daniel Doubleday (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1956) Convert row cache to row+filter cache
Date Thu, 05 Jan 2012 13:07:39 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13180355#comment-13180355
] 

Daniel Doubleday commented on CASSANDRA-1956:
---------------------------------------------

Well that is pretty much exactly what the initial patch does.

The only inefficiency as noted above are deletions which are hard to handle without invalidation
and now that we have them ttl columns.

That is when 'CACHING FIRST 100' implies a promise that the user will receive 100 valid cols.
The easy way out would be to state that 100 includes tombstones.


                
> 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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