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https://issues.apache.org/jira/browse/CASSANDRA-3073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13126973#comment-13126973
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Jonathan Ellis commented on CASSANDRA-3073:
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bq. could we add a config option to control to choose the SlabAllocator or the
native one
I'm fine with adding an option.
bq. by the time minor GC happens, some old columns in the Region has been
superceded and are useless
the Column objects themselves aren't the problem, since they are all the same
[shallow] size. It's the name, value, and key buffers that cause fragmentation,
and those are what we clone into the arena regions.
> liveSize() calculation is wrong in case of overwrite
> ----------------------------------------------------
>
> Key: CASSANDRA-3073
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3073
> Project: Cassandra
> Issue Type: Bug
> Reporter: Yang Yang
> Priority: Minor
> Attachments:
> 0001-liveSize-is-different-from-throughput-particularly-w.patch
>
>
> currently liveSize() is the sum of currentThroughput.
> this definition is wrong if most of the operations are overwrite, or counter
> (which is essentially overwrite).
> for example, the following code should always keep a single entry in db, with
> one row, one cf, one column, and supposedly should have a size of only about
> 100 bytes.
> connect localhost/9160;
> create keyspace blah;
> use blah;
> create column family cf2 with memtable_throughput=1024 and
> memtable_operations=10000 ;
> set the cassandra.yaml
> memtable_total_space_in_mb: 20
> to make the error appear faster (but if u set to default, still same issue
> will appear)
> then we use a simple pycassa script:
> >>> pool = pycassa.connect('blah')
> >>> mycf = pycassa.ColumnFamily(pool,"cf2");
> >>> for x in range(1,10000000) :
> ... xx = mycf.insert('key1',{'col1':"{}".format(x)})
> ...
> you will see sstables being generated with only sizes of a few k, though we
> set the CF options to get high SSTable sizes
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