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List:       kde-pim
Subject:    Re: [Kde-pim] How to force sync to disk
From:       Pablo Sanchez <pablo () blueoakdb ! com>
Date:       2014-11-18 11:36:52
Message-ID: 546B2F54.1060908 () blueoakdb ! com
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[ Comments below, in-line ]

On 11/18/2014 03:38 AM, Martin Steigerwald wrote:
> 

Hi everyone,

> I am not aware of a command I can use to tell Akonadi to flush out file_db_data 
> to final location, but I think usually Akonadi will do so after a while. I 
> think to recall that there is a hard coded timeout for this.
>
> Maybe a developer can shed more light on this.

When Akonadi is using MySQL as its back end storage repository, there's
no `checkpoint' command to synchronize the DBMS' pages in memory to
disk.  According to the link below, MySQL handles the synchronization
asynchronously:

https://dev.mysql.com/doc/refman/5.0/en/innodb-checkpoints.html

When Akonadi issues DELETE's, the DELETEs are processed by MySQL.  Since
MySQL conforms to ACID [1] (unless configured not to), the changes are
written to its internal log.

If I recall, the way MySQL is configured, we may lose up [2] to a second
or so of information, and in return we speed up write-performance.  I
suspect Akonadi has mechanisms in place to handle this situation.

[1] - https://en.wikipedia.org/wiki/ACID

[2] - this may happen if MySQL is kill'd during mid-transaction.  I'd
have to bring up my VM to confirm the setting (I'm in mid-upgrade at the
moment).

Cheers,

--
Pablo Sanchez - Blueoak Database Engineering, Inc
Ph:    819.459.1926         Blog:  http://pablo-blog.blueoakdb.com
iNum:  883.5100.0990.1054

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