Note that the single problem with this is that objects that _aren't_
actually being deleted (and that might be referenced by the application)
are suddenly evicted - and any subsequent modifications are lost.
Actually, the disable-when-instances-are-loaded option can almost be used
to emulate the evict-all-instances option. The user just has to manually
evict any instances that might cause mass update to be disabled.
P.S. I just realised that this is more than a 2 hr job. I was hoping to
reuse the existing HQL translation code completely. Unfortunately,
databases dont like:
delete from foos f where f.count > 10
You aren't allowed to use aliases in a DELETE. I wasn't really aware of
that (makes sense).
But anyway, its still certainly doable.
|---------+---------------------------->
| | "Domagoj |
| | Jugovich" |
| | <[EMAIL PROTECTED]>|
| | |
| | 04/08/03 05:23 PM|
| | |
|---------+---------------------------->
>------------------------------------------------------------------------------------------------------------------------------|
|
|
| To: <[EMAIL PROTECTED]>
|
| cc:
|
| Subject: Re: [Hibernate] Mass Deletes
|
>------------------------------------------------------------------------------------------------------------------------------|
and fourth : issue a delete and flush all cache
but disable-when-instances-are-loaded is OK, when we want a mass delete we
must take care that we don't have nothing loaded of that class, it is more
logical because this mass-delete feature is primarily for speed/performance
so we should tradeoff everithing , lifecycle, caching, if we want
lifecacyle
etc.. we do normal deletion. But how will be the choosing implemented (mass
or normal delete) ?
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, August 04, 2003 5:36 AM
Subject: [Hibernate] Mass Deletes
> Many users have asked for
>
> session.delete("from Foo foo where foo.count=0");
>
> to issue a single SQL DELETE. This is certainly not possible for objects
> with collections or cascades (though it might not matter if we ignore
> Lifecycle callback; not sure). For other classes it is conceptually
> possible.
>
> Now, this is really quite easy to implement - it would take me about 1-2
> hours to do it.
>
> But my big problem is: how do we know which _loaded_ objects were
deleted?
> I don't think there is any good way to do this. All we get back from
DELETE
> is a row count.
>
> * Do we issue a SELECT beforehand, to fetch the ids ..... and then
issue
> the delete?
> * Do we just disable mass delete for classes which have loaded
instances?
> * Is it simply not worth it?
>
> The select-then-delete option doesn't seem particularly better than the
> current situation when JDBC batch updates are enabled. The
> disable-when-instances-are-loaded option looks like it would work, but
only
> for some very limited usecases (though it may work for the usecases we
are
> most interested in).
>
>
> Thoughts?
>
>
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