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From "Robert Stupp (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-8231) Wrong size of cached prepared statements
Date Fri, 31 Oct 2014 20:23:34 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-8231?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Robert Stupp updated CASSANDRA-8231:
------------------------------------
    Attachment: Unsafes.java

Attached {{Unsafes.java}} that I've written some time ago to calculate heap memory occupied
by any object. Although it's a bit over-designed, it solves the problem of calculating the
same object instance twice.
In order to solve the issue of taking irrelevant fields into account, I'd propose some annotation
to be added to those fields - or to provide a set of classes to exclude from calculation.

> Wrong size of cached prepared statements
> ----------------------------------------
>
>                 Key: CASSANDRA-8231
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8231
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Jaroslav Kamenik
>            Assignee: Benjamin Lerer
>         Attachments: 8231-notes.txt, Unsafes.java
>
>
> Cassandra counts memory footprint of prepared statements for caching purposes. It seems,
that there is problem with some statements, ie SelectStatement. Even simple selects is counted
as 100KB object, updates, deletes etc have few hundreds or thousands bytes. Result is that
cache - QueryProcessor.preparedStatements  - holds just fraction of statements..
> I dig a little into the code, and it seems that problem is in jamm in class MemoryMeter.
It seems that if instance contains reference to class, it counts size of whole class too.
SelectStatement references EnumSet through ResultSet.Metadata and EnumSet holds reference
to Enum class...



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