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From "Aleksey Yeschenko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4175) Reduce memory, disk space, and cpu usage with a column name/id map
Date Thu, 20 Nov 2014 20:50:36 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14219973#comment-14219973
] 

Aleksey Yeschenko commented on CASSANDRA-4175:
----------------------------------------------

bq. Probably a stupid question, but will making the schema be set external to the SSTable
make it harder or impossible to move an sstable to a different cluster, since the column data
is no longer there?

Nah, we can just encode the {name -> id} map in sstable metadata.

> Reduce memory, disk space, and cpu usage with a column name/id map
> ------------------------------------------------------------------
>
>                 Key: CASSANDRA-4175
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4175
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: Jason Brown
>              Labels: performance
>             Fix For: 3.0
>
>
> We spend a lot of memory on column names, both transiently (during reads) and more permanently
(in the row cache).  Compression mitigates this on disk but not on the heap.
> The overhead is significant for typical small column values, e.g., ints.
> Even though we intern once we get to the memtable, this affects writes too via very high
allocation rates in the young generation, hence more GC activity.
> Now that CQL3 provides us some guarantees that column names must be defined before they
are inserted, we could create a map of (say) 32-bit int column id, to names, and use that
internally right up until we return a resultset to the client.



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