[jira] Updated: (CASSANDRA-1956) Convert row cache to row+filter cache

["Stu Hood (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-1956?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Stu Hood updated CASSANDRA-1956:
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    Comment: was deleted

(was: Thanks for the patch Daniel! We actually have existing 'filter' implementations (in {{org.apache.cassandra.db.filter}}) that I think would make the most sense for use aside cache entries.

> What about just invalidating (removing from the cache) the row on delete and letting it get rebuild on the next read?
Also, regarding the "tombstones in cache" problem: I believe it came up in IRC the other day. The solution that seemed closest to our existing methods was to keep the tombstones in cache, but to add a thread that periodically walked the cache to perform GC (with our existing GC timeout) like we would during compaction.)

> 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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