[jira] [Comment Edited] (CASSANDRA-9472) Reintroduce off heap memtables

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

    [ https://issues.apache.org/jira/browse/CASSANDRA-9472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15105169#comment-15105169 ] 

Benedict edited comment on CASSANDRA-9472 at 1/18/16 11:27 AM:
---------------------------------------------------------------

Thanks for finishing up finding the work [~Stefania].

It looks mostly good, but I would probably modify it a little from its current representation:

* Storing an {{offheap}} variable in {{BTreeRow}} looks error-prone to maintain, and forwarding all calls in {{AbstractBTreeRow}} to a virtual {{onHeapCopy}} is unnecessarily costly for objects that never are offheap.  I think it makes more sense for the {{AtomicBTreePartition}} to check f it stores on/offheap data when answering a query, and to return a suitable iterator that knows to copy on-heap when necessary - much as it used to, but moved one step outwards so that it can capture {{DecoratedKey}} and {{staticRow}}
* As far as segmentation faults on {{toString}} when {{peer == 0}}, this is only a problem for the debugger, because we don't call {{toString()}} ourselves.  I don't mind adding guards, but they should really throw exceptions since any access to these objects when they've been freed is unequivocally a bug.

Let me know your thoughts (and I'll finish this up, if we're in agreement).


was (Author: benedict):
Thanks for finishing up finding the work [~Stefania].

It looks mostly good, but I would probably modify it a little from its current representation:

* Storing an {{offheap}} variable in {{BTreeRow}} looks error-prone to maintain, and forwarding all calls in {{AbstractBTreeRow}} to a virtual {{onHeapCopy}} is unnecessarily costly for objects that never are offheap.  I think it makes more sense for the {{AtomicBTreePartition}} to check f it stores on/offheap data when answering a query, and to return a suitable iterator that knows to copy on-heap when necessary - much as it used to, but moved one step outwards so that it can capture {{DecoratedKey}} and {{staticRow}}
* As far as segmentation faults on {{toString}} when {{peer == 0}}, this is only a problem for the debugger, because we don't call {{toString()}} ourselves.  I don't mind adding guards, but they should really throw exceptions since any access to these objects when they've been freed is unequivocally a bug.

Let me know your thoughts.

> Reintroduce off heap memtables
> ------------------------------
>
>                 Key: CASSANDRA-9472
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9472
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Benedict
>            Assignee: Stefania
>             Fix For: 3.x
>
>
> CASSANDRA-8099 removes off heap memtables. We should reintroduce them ASAP.



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