[hibernate-dev] Using a checksum for version properties

[Max Rydahl Andersen]

Look at optimistic-lock in the docs.

/max

> Hi,
>
> We have some database tables that we can't add version columns to so I
> would like to instead create a version number by using checksums on
> the rows.
>
> I'm thinking specifically of Oracle here but I assume other platforms
> may have equivalent features; the sort of query I am looking at using
> is...
>
> select id, name, salary,
>             dbms_crypto.hash(utl_raw.cast_to_raw(id || name ||
> salary), 1) as version
> from employees
>
> In this example, the version column is populated with the MD4 sum of
> the three properties.
>
> I've tried to create a custom EntityPersister but it looks like I'll
> need to dig deeper. My plan would be to create the checksum code
> automatically depending on the 'versionability' of the properties.
>
> If this sounds useful/sane I am happy to work on a patch.
>
> Regards,
> Tom
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