[jira] Commented: (CASSANDRA-16) Memory efficient compactions

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

    [ https://issues.apache.org/jira/browse/CASSANDRA-16?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12689793#action_12689793 ] 

Jonathan Ellis commented on CASSANDRA-16:
-----------------------------------------

High level, you want to make a CF deserializer that implements Iterable<IColumn> (with buffering of course).  Then have merge operate on those iterables instead of full CFs.

It should be fairly self-contained, really.  I think you only need to worry about the code in this small part of doCompaction:

{code}
	                                if(columnFamilies.size() > 1)
	                                {
	    		                        merge(columnFamilies);
	                                }
			                        // deserialize into column families                                    
			                     columnFamilies.add(ColumnFamily.serializer().deserialize(filestruct.getBufIn()));
{code}

and then the sub-methods of merge of course.

> Memory efficient compactions 
> -----------------------------
>
>                 Key: CASSANDRA-16
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-16
>             Project: Cassandra
>          Issue Type: Improvement
>         Environment: All
>            Reporter: Sandeep Tata
>
> The basic idea is to allow rows to get large enough that they don't have to fit in memory entirely, but can easily fit on a disk. The compaction algorithm today de-serializes the entire row in memory before writing out the compacted SSTable (see ColumnFamilyStore.doCompaction() and associated methods).
> The requirement is to have a compaction method with a lower memory requirement so we can support rows larger than available main memory. To re-use the old FB example, if we stored a user's inbox in a row, we'd want the inbox to grow bigger than memory so long as it fit on disk.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.