Gavin King wrote:
In my private chats with people, it seems we all agree that currently, Hibernate2 association fetch strategy configuration is confusing and has nonsensible defaults. I've spent quite a lot of time thinking about how we could clean this up without breaking 2.x mapping documents too much, and come to the conclusion that this would be the best approach:
(1) make lazy default to true on both <class> and <collection> mapping elements; if a class cannot be proxied, laziness is transparently disabled; make it clear that we intend laziness to be used 99% of the time
Most controversial part but I'm +1 from a pragmatic perspective. However, I can understand people thinking it's a bit too much since it's not 100% sure you can lazy, and the '1 query to bind them all' is a very common urban legend.
We should emphasize *a lot* the fetch HQL keyword (complex to understand with its 1 collection fetched only). It'll be (if not already) a key tool.
(2) provide <hibernate-mapping default-lazy="false">, to override this new default for backward compatibility purposes
+1
(3) deprecate (remove?) the confusingly named outer-join attribute
+1, my favorite
(4) introduce the fetch attribute, where, at least initially, the options are fetch="join|select"; eventually we may add other options like fetch="immediate-select"
+1 immediate-select means unlazy but wo join, correct ?
Questions:
* The default should be fetch="select" for collections, what should the default be for to-one associations? I suppose that purely for backward compatibility purposes we need fetch="auto|join|select", where auto is the default, and chooses "select" for a lazy-enabled class.
To stay consistent with (4), add a default value (I know one more). I've never been fond of the 'auto'-magical configuration. It has confused tons of guys I've worked with.
* Should we provide XSLT stylesheets to transform 2.x mapping to 3.0 mappings, rather than providing backward compatibility at the mapping document level, by adding default-lazy and continuing to support the outer-join attribute?
-0, some guys had the old style in mind, and they might want to keep it. The tool convertor is a one shot, not an every day choice.
* Anything else needed?
We *must* provide a clear and clean material on what to do to lazy, fetch a collection a to-one etc... We'll need a clean separation between H2 and H3 docs (whether wiki or not).
* Does this suck?
Nope, be ready to argue kindly with a lot of guys :-)
-- Emmanuel Bernard [EMAIL PROTECTED] http://www.hibernate.org
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