On Mon 05 Dec 2011 12:59:19 PM CST, David Mansfield wrote:
> While I do agree wholeheartedly with most of what you say, I do think
> it's unfair to say that the requirement is "fundamentally broken". That
> label should be reserved for SQL itself ;-)
>
> If there is some opaque business rule R that operates on a large set of
> input data, and that rule is implemented in Java, using Hibernate to get
> the input data, it's quite possible that the rule generates a large list
> of entities to retrieve. Is there a better way to batch fetch a
> s***load of specific entities, given a List or Set of identifiers?
for ( Long identifier : setOrListOfIdentifiers ) {
session.get( YourEntity.class, identifier );
}
>
> Here's another scenario. Suppose I have "master" table, suppose
> "orders". And another table "order_line_items",which is a one-to-many,
> and another table "order_state_change" which is also one-to-many. And
> suppose also that there is a somewhat complex (computationally or I/O
> cost) set of conditions to filter the retrieved results.
I have to be honest. I do not see at all how this bears on the issue
of limiting the number of literals in an IN list.
> There is a huge Inefficiency with multiple one-to-many joins (and no
> global temp table) because you have to either:
> 1) execute the complex where clause once for each one-to-many
> 2) build in your temp segment then fetch across your network a
> Cartesian product of the one-to-manys
> 3) use an "in (id1, id2, id3...)" clause for each one-to-many
Yes, Hibernate itself can attempt to build a query of this sort with
the "subselect" fetching strategy. Which is another potential problem
area for this..
I am not unsympathetic to the desire to have Hibernate (aka, "someone
else") handle this for you. Its just that I have not seen a
suggestion to handle this in a reasonably generic manner. If I hear
one, then maybe I will change my mind.
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st...@hibernate.org
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