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From "Jonathan Ellis (Updated) (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-3743) Lower memory consumption used by index sampling
Date Tue, 24 Jan 2012 16:32:40 GMT


Jonathan Ellis updated CASSANDRA-3743:

    Attachment: 3743-trunk-trim.txt

Slight update attached to use positions.trimToSize instead of leaving an "orphan" arraylist
around.  As mentioned above, the size difference is negligible.

Question: is the getKeySamples transform still necessary, or can we just cast the keys collection?

Or could we just make it a List of DK in the first place instead of RP?
> Lower memory consumption used by index sampling
> -----------------------------------------------
>                 Key: CASSANDRA-3743
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.0.0
>            Reporter: Radim Kolar
>            Assignee: Radim Kolar
>              Labels: optimization
>             Fix For: 1.1
>         Attachments: 3743-trunk-trim.txt, 3743-trunk.txt, cassandra-3743-codestyle.txt
> currently is implemented as ArrayList of KeyPosition
(RowPosition key, long offset)i propose to change it to:
> RowPosition keys[]
> long offsets[]
> and use standard binary search on it. This will lower number of java objects used per
entry from 2 (KeyPosition + RowPosition) to 1 (RowPosition).
> For building these arrays convenient ArrayList class can be used and then call to .toArray()
on it.
> This is very important because index sampling uses a lot of memory on nodes with billions

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