No! That is NOT what we are suggesting. It would be just two SQL
statements.
|---------+------------------------------------------->
| | Patrick Burleson |
| | <[EMAIL PROTECTED]> |
| | Sent by: |
| | [EMAIL PROTECTED]|
| | ceforge.net |
| | |
| | |
| | 04/08/03 11:44 PM |
| | |
|---------+------------------------------------------->
>------------------------------------------------------------------------------------------------------------------------------|
|
|
| To: [EMAIL PROTECTED]
|
| cc:
|
| Subject: RE: [Hibernate] Mass Deletes
|
>------------------------------------------------------------------------------------------------------------------------------|
I got in on this thread late, but if I understand what people are talking
about, the
select-then-delete model doesn't work well on large datasets. This is one
of the drawbacks to
Entity Beans for our organization. Trying doing that model for 10K rows and
you quickly see how
much that extra statement costs you when you can do it in less than a
second with a simple delete.
Patrick
--- Odd Moller <[EMAIL PROTECTED]> wrote:
> I don't understand the drawbacks with the select-then-delete alternative.
> Doesn't it just mean one additional statement to the database?
>
> ///Odd Moller
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
> Sent: den 4 augusti 2003 05:36
> To: [EMAIL PROTECTED]
> 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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