[jira] [Commented] (CASSANDRA-5357) Query cache

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-5357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13773111#comment-13773111 ] 

Jonathan Ellis commented on CASSANDRA-5357:
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Getting back to this now that 2.0.1 is done.  Sounds reasonable in general.  Comments:

# I don't think dropping RowCacheSentinel is valid, unfortunately.  Otherwise we still have the same problem as CASSANDRA-3862.  (Write can invalidate the row, just before cache adds the pre-write value to it, so stale data will be cached indefinitely.)
# Serializing the entire QueryCacheValue for each lookup is going to kill performance on hot partitions.  (Since you have to deserialize a large chunk of filters to just do the existence check.)  Suggest that serializing just the CF data is going to work better.
# {{TODO do something here}} looks important :)
# "There could be any number of queries but the data will not be repeated within them."  Clever.
# "There is a property which user can enable to cache the whole row." Not really a fan but I guess existing row cache users will demand it. :-|
# "we might be pulling the whole data into memory" -- if there's room, that's fine, but exceeding the configured memory budget is Bad.  As long as we don't do that I'm fine.
                
> Query cache
> -----------
>
>                 Key: CASSANDRA-5357
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5357
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Jonathan Ellis
>            Assignee: Vijay
>
> I think that most people expect the row cache to act like a query cache, because that's a reasonable model.  Caching the entire partition is, in retrospect, not really reasonable, so it's not surprising that it catches people off guard, especially given the confusion we've inflicted on ourselves as to what a "row" constitutes.
> I propose replacing it with a true query cache.

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