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| Re: [CDO] scalability of to-many references [message #500908 is a reply to message #500670] |
Mon, 30 November 2009 09:20   |
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Hi Lothar,
It seems reasonable to optimize DB access for large collections in
auditing mode. I suggest that you file a bugzilla to discuss possible
solutions and attach patches. Stefan will want to add his opinion as well.
Cheers
/Eike
----
http://thegordian.blogspot.com
http://twitter.com/eikestepper
Lothar Werzinger schrieb:
> Hi,
>
> I am currently doing some scalability tests and the current way that to-many
> references are mapped to the database won't scale to large numbers of
> objects contained in the to-many reference.
>
> This is due to the fact that when auditing is used (mandatory for my
> application) every time one ore more object references are added to the
> to-many reference the whole list of object references (with a new CDO
> version) is added to the table containing the to-many references. So if the
> to-many reference contains one million object references and you add
> another one then one million and one rows need to be inserted to the
> database.
>
> I propose a modified mapping that keeps auditibility without having to
> replicate all the old object references.
>
> As to-many references basically have tow operations (add and object and
> remove an object) I propose to split the 'cdo_version' column into
> two: 'cdo_version_added' and 'cdo_version_removed'.
> If a new object gets added to the to-many reference, then
> it's 'cdo_version_added' gets set. If it is removed
> it's 'cdo_version_removed' gets set accordingly.
>
> With this enhanced mapping only one row for each inserted object is used
> unless the identical object is reinserted after it was removed. Only in
> that case 'duplicate' rows (with different 'cdo_version_added'
> and 'cdo_version_removed') need to be created.
>
> The new mapping will be almost as effective retrieving the to-many reference
> for a given CDO version.
> The old (current) query would be like this:
> SELECT * FROM X WHERE cdo_version=?
> and the new (proposed) query would be
> SELECT * FROM X WHERE cdo_version_added <= ? AND (cdo_version_removed is
> NULL OR cdo_version_removed > ?)
>
> Please let me know your thoughts.
>
> P.S.
> I am currently unfamiliar with the code that does the DB mapping, but I
> would be willing to help with the new mapping if I can get the necessary
> pointers where I need to focus my reading to modify and test the proposed
> mapping.
>
> Lothar
>
>
>
Cheers
/Eike
----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper
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