[hibernate-dev] HHH-10478 : OperationContext

[Gail Badner]

Replying for consideration for 6.0.

On Mon, Feb 8, 2016 at 6:12 AM, Steve Ebersole <steve at hibernate.org> wrote:

> This is going to have to wait post-5.1 as I mentioned earlier if this was
> not ready prior to last week.
>
> I have just too much on my plate to look at this over 2 days.
>
> On Mon, Feb 8, 2016 at 12:29 AM Gail Badner <gbadner at redhat.com> wrote:
>
>> The POC [1] assumes that we only need a single OperationContext for each
>> type of operation. OperationContextManager has a Map of OperationContext
>> by
>> OperationContextType. Each OperationContext object is lazily created on
>> the
>> first occurence of the corresponding type of operation.
>>
>> Currently, when an operation is initiated (e.g., by Session.merge( entity
>> )), OperationContextManager [2] does the following:
>> - calls ManageableOperationContext#beforeOperation, which puts the
>> OperationContext "in progress";
>> - executes the operation, which performs cascades according to mappings;
>> - calls ManageableOperationContext#afterOperation, which puts the
>> OperationContext in an invalid state that is "not in progress".
>>
>> When an operation cascades to other entities, the same OperationContext is
>> used.
>>
>> Obviously, OperationContextManager needs to know if an operation is
>> "top-level" (meaning that the operation is on the original entity, and not
>> cascaded). In the POC, if the relevant OperationContext is not in progress
>> at the time that an opeation is initiated, then OperationContextManager
>> assumes that the operation is top-level. If the OperationContext is "in
>> progress", then OperationContextManager assumes that this is a cascaded
>> operation.
>>
>> I am not sure this is always correct. Can anyone think of a case where
>> this
>> could break down?
>>
>> In the POC, the following EventSource methods that contain an argument for
>> the operation cache has been deprecated and is no longer used because the
>> contents of that argument has been moved into an OperationContext:
>>
>> public void merge(String entityName, Object object, Map copiedAlready)
>> public void persist(String entityName, Object object, Map createdAlready)
>> public void persistOnFlush(String entityName, Object object, Map
>> copiedAlready)
>> public void refresh(String entityName, Object object, Map
>> refreshedAlready)
>> public void delete(String entityName, Object child, boolean
>> isCascadeDeleteEnabled, Set transientEntities)
>>
>> Before the POC, it was the above methods that indicated that it was not
>> top-level. If it turns out that having a single OperationContext is not
>> valid, then there needs to be some other way to determine if the operation
>> was top-level.
>>
>> I had originally planned to use PersistenceContext#getCascadeLevel == 0 to
>> indicate an operation was at the top-level, but I found that won't work
>> for
>> some operations. For example, the cascade level for a top-level delete can
>> be > 1 when deleting orphans due to merge or save-or-update operations.
>> Another example is that cascade level is not 0 on top-level save-or-update
>> while flushing.
>>
>> I have some ideas to work around this, but I didn't want to get too far
>> down that path if it wasn't an issue.
>>
>> Thanks,
>> Gail
>>
>> [1]
>>
>> https://github.com/gbadner/hibernate-core/blob/3d0e2378cb998788b3205afb1e15c443c5ba77e8/hibernate-core/src/main/java/org/hibernate/engine/operationContext/internal/OperationContextManager.java
>> [2]
>>
>> https://github.com/gbadner/hibernate-core/blob/3d0e2378cb998788b3205afb1e15c443c5ba77e8/hibernate-core/src/main/java/org/hibernate/engine/operationContext/internal/OperationContextManager.java#L132
>>
>>
>> On Fri, Feb 5, 2016 at 8:17 PM, Gail Badner <gbadner at redhat.com> wrote:
>>
>> > I've created a gist with an overview of the design:
>> > https://gist.github.com/gbadner/f0e635e8fba7b84af233 . I will add a new
>> > section tomorrow about possible shortcomings.
>> >
>> > Here is my POC:
>> >
>> https://github.com/hibernate/hibernate-orm/compare/master...gbadner:HHH-10478-OperationContext
>> > . Although no tests fail, the approach may be too simple to model what
>> is
>> > necessary.
>> >
>> > At this point the POC is squashed down to 1 commit:
>> >
>> https://github.com/hibernate/hibernate-orm/commit/3d0e2378cb998788b3205afb1e15c443c5ba77e8
>> >
>> > Have a look and feel free to comment.
>> >
>> > Thanks,
>> > Gail
>> >
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>