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From "Vijay (Updated) (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-1956) Convert row cache to row+filter cache
Date Thu, 09 Feb 2012 07:31:00 GMT


Vijay updated CASSANDRA-1956:

    Attachment: 0001-commiting-block-cache.patch

This patch is not complete yet i just wanted to show and see what you guys think about this...
This patch is something like a block cache where it will cache blocks of columns where the
user can choose the block size and if the query is within the block we are good by just pulling
the block into memory else we will scan through the blocks and get the required blocks. Updates
can also scan through the blocks and update them... The good part here is this should have
lower memory foot print than Query cache but it should also solve the problems which we are
discussing in this ticket. Let me know thanks! Again there is more logic/cases to be handled,
Just a prototype for now.
> Convert row cache to row+filter cache
> -------------------------------------
>                 Key: CASSANDRA-1956
>                 URL:
>             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-commiting-block-cache.patch,
0001-re-factor-row-cache.patch, 0001-row-cache-filter.patch, 0002-1956-updates-to-thrift-and-avro-v0.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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