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Date: Fri, 7 Jun 2013 18:34:22 +0000 (UTC)
From: "Jonathan Ellis (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <JIRA.12551683.1334871582661.86219.1370630062726@arcas>
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Subject: [jira] [Commented] (CASSANDRA-4175) Reduce memory (and disk) space
 requirements with a column name/id map
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    [ https://issues.apache.org/jira/browse/CASSANDRA-4175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13678280#comment-13678280 ] 

Jonathan Ellis commented on CASSANDRA-4175:
-------------------------------------------

If you're going to respond to a comment over a year old, you should at least read the newer ones.  There's no reason to use ZK now that we have CAS available.
                
> Reduce memory (and disk) space requirements 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
>             Fix For: 2.1
>
>
> 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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