[hibernate-dev] SingleTableEntityPersister memory footprint in 5.3

[Sanne Grinovero]

On 4 May 2018 at 19:45, Gail Badner <gbadner at redhat.com> wrote:
> I don't think the batching strategies actually changed when we moved to load
> plans.
>
> Is the problem that each loader is taking considerably more memory?

Yes that's right.

>
> On Fri, May 4, 2018 at 5:41 AM, Guillaume Smet <guillaume.smet at gmail.com>
> wrote:
>>
>> On Fri, May 4, 2018 at 11:48 AM, Sanne Grinovero <sanne at hibernate.org>
>> wrote:
>>
>> > thanks for investigating. Steve in chat mentioned the option of
>> > creating these EntityLoaders lazily: as while they need to be reused,
>> > it's possible many of them are never really used.
>> >
>> > I think that's a very interesting observation, is that what you plan to
>> > explore?
>> >
>>
>> Yes, it's one of the things we should explore.
>>
>>
>> > I see two difficulties:
>> >  - you'd need thredsafe code, yet we don't want barriers on this area.
>> > Will probably need features such as lazy set, yet these would need
>> > even more objects allocated if you're not careful.
>> >  - we always prefer fail-at-boot validation, so we'd need to make sure
>> > even if you don't build them all, we can at least make sure we'll be
>> > able to build them later.
>> >
>>
>> Well, the idea is to prototype something on the memory usage front, then
>> we
>> can discuss further what we want to do with it and if it's worth refining
>> it and spending more time on it.
>>
>> If we end up choosing this path, be sure we'll be bugging you for advice
>> on
>> concurrency and performance :).
>>
>>
>> > Additionally there's the idea to see if any such Loader instance could
>> > be reused - probably using a cache which we clear at end of bootstrap
>> > - yet since Steve mentioned this would be a significant change let's
>> > not try to push it in 5.3.
>> >
>> > Finally, a simple one: I have the impression that loader's Map could
>> > be made into a plain array, or a custom structure which would then be
>> > ideal to support lazy creation of loaders. With the exception of two
>> > special strings - which will needt to be treated specially - all other
>> > keys are enums.
>> >
>>
>> Yeah, I'll play with a few ideas and see what I can do. I'm not yet sure
>> if
>> not knowing the code base will be a thing in my favor or not. At least I
>> don't have preconceived ideas :].
>>
>>
>> > Whatever you choose to try, let's keep significant changes for 6 only :)
>> >
>>
>> Steve was saying that this whole thing wouldn't be an issue in 6.
>>
>> --
>> Guillaume
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>
>