Steve, is this related to https://hibernate.atlassian.net/browse/HHH-3949?
On Thu, Mar 1, 2018 at 10:11 PM, Gail Badner <gbad...@redhat.com> wrote: > This is not necessarily needed for 5.3.0, but I would like to get it into > the 5.3 branch. > > So far, there is one change to an SPI, Queryable#lazyGroupSelectFragment > is added: > > public String lazyGroupSelectFragment( > String tableAlias, > String suffix, > String fetchGroupName); > > The method gets implemented in AbstractEntityPersister. > > I don't think it's possible to create a default method in Queryable > because the method needs access to private/protect methods in > AbstractEntityPersister. > > If I don't get HHH-11223 in for 5.3.0, should I at least push the SPI > change for 5.3.0? > > On Thu, Mar 1, 2018 at 9:55 PM, Gail Badner <gbad...@redhat.com> wrote: > >> Hi, >> >> Currently, when a lazy group is loaded that has associations, there are 2 >> SQL statements executed. >> >> For example, suppose the DEFAULT lazy group contains the following: >> >> * Order#customer is a lazy many-to-one association; >> >> * Order#text is a lazy LOB. >> >> >> When one of these properties is referenced, Hibernate loads both of them. >> >> >> Currently, it takes 2 SQL statements to get the association loaded. >> >> >> 1) Loads #text and the FK value for #customer (select o.text, >> o.customer_id from orders o where o.id = ?) >> >> 2) Loads the state for #customer (select ... from customers c where c.id = >> ?) >> >> >> In other words, FetchMode.SELECT is used to load associations in a lazy >> group. >> >> >> HHH-11223 involves combining the 2 SQL statements into a single >> statement using a join (i.e., using FetchMode.JOIN), but only when at least >> one of the following is true: >> >> >> * caching is disabled for the SessionFactory (e.g., >> hibernate.cache.use_second_level_cache=false; >> >> * caching is not enabled for "get" operations (i.e., >> session.getCacheMode().isGetEnabled() == false); >> >> * the associated entity type (and subclasses?) is not cached >> >> HHH-11223 only mentions to-one associations, but I think collections in a >> lazy group could also be loaded using a join as well. >> >> I think I'm pretty close, but I need to do a lot more testing to ensure >> it covers things like: >> >> * lazy association in composite ID >> * lazy association in an embeddable >> * lazy association in a secondary table >> * lazy association in a subclass >> * too many bags >> >> This is what I have implemented so far: https://github.com/hibern >> ate/hibernate-orm/pull/2170 >> >> At the moment, I'm not looking for a comprehensive review. I'm just >> looking for a review of the overall design. >> >> I don't want to get into the nitty-gritty here, but, basically, I've >> created a new type of AbstractLoadPlanBasedEntityLoader, LazyGroupLoader, >> which loads the lazy group properties into the existing entity. >> >> If caching is disabled for the SessionFactory, then one loader is >> constructed per lazy group, and associations will be loaded using >> FetchMode.JOIN. >> >> If caching is enabled for the SessionFactory, then 2 loaders are >> constructed per lazy group. One loader is used when caching is enabled for >> "get" operations (using Fetch.SELECT for cached associated >> entities/collections; Fetch.JOIN for other associations). The other loader >> is used when caching is disabled for "get" operations. >> >> Here are some of the changes to the default behavior (described above) >> that could be useful: >> >> 1) Change all associations in lazy groups to be loaded using >> FetchMode.SELECT (as is currently done without the fix), or using >> FetchMode.JOIN (regardless of caching). A new configuration property could >> be added: >> >> hibernate.bytecode.lazyGroup_association_fetchMode=(default | select | >> join ) >> >> 2) Allow the FetchMode to be configured for a particular lazy >> association. According to the documentation , @Fetch can't be used for >> this because, "... FetchMode.JOIN acts as a FetchType.EAGER strategy. Even >> if we mark the association as FetchType.LAZY, the FetchMode.JOIN will load >> the association eagerly." >> >> A new annotation could be introduced: @LazyFetch. >> >> Comments or suggestions? >> >> Thanks, >> Gail >> >>  http://docs.jboss.org/hibernate/orm/5.2/userguide/html_s >> ingle/Hibernate_User_Guide.html#fetching-fetchmode-join >> > > _______________________________________________ hibernate-dev mailing list email@example.com https://lists.jboss.org/mailman/listinfo/hibernate-dev