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From "Benjamin Lerer (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-8231) Wrong size of cached prepared statements
Date Wed, 19 Nov 2014 08:16:34 GMT

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

Benjamin Lerer updated CASSANDRA-8231:
--------------------------------------
    Attachment: CASSANDRA-8231.txt

This patch replace the jamm version 0.2.8 by the version 0.3.0 which support the {{Unmetered}}
annotation on type.

The {{ignoreKnownSingleton}} option of {{MemoryMeter}} was already excluding {{Class}} and
{{Enum}} instances. So only the {{CFMetadata}}, {{AbstractType}} and {{Function}} had to be
marked with the {{Unmetered}} annotation. 

I used the {{enableDebug}} option from {{MemoryMeter}} to verify that the measured instances
were the expected ones. 

> 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, CASSANDRA-8231.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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