[POC][IMP] mail, *: post creation messages in batch.

[Feyensv]

Even if a creation subtype is specified on the model.

project.task records population is unexpectedly slow.
Performance analysis has shown a major bottleneck in mail, in the mail.thread create override.

• Followers insertion mail_followers._insert_followers (8%` of the population time)
• message_post calls (45% of the population time)
  When a specific mail subtype is given for creation on the model (_creation_subtype method), the messages are not logged
  in batch but posted one by one through message_post.

This PR aims to improve the project population performance, mainly by targeting mail related performance problems.

1. update message_post to allow posting identical messages in batch, on multiple threads (and its overrides).
   And use it in mail.thread.create to post messages in batches, even when specific mail creation subtype are specified, posting
   one batch by mail subtype specified (as some models may use different subtypes for different records of same model).
2. clean/adapt/improve methods related to message_post related methods (message_post_after_hook, ...) and their overrides:

• avoid useless operations if possible
• cleaner and more consistent API & docstrings

Perf gains:

• message_post: 45% --> 25%
• creation_subtype: 2% -> 0%

Population Time:
~100s --> ~60s

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[seb-odoo]

Promising change for performance, let me know when it's getting ready for review.

[tde-banana-odoo]

I still wonder if it would not be better to first clean some low level methods in mail thread and re-order the way we post and notify before trying to post in batch ... especially that as import does not go through any thread code your performance improvements are mainly useful for populate which is not a production tool.

[Feyensv]

Promising change for performance, let me know when it's getting ready for review.

IMO it's ready (the error in the enterprise build is strange, I launched a rebuild), but we will have to convince tde ^^.

I still wonder if it would not be better to first clean some low level methods in mail thread and re-order the way we post and notify before trying to post in batch ... especially that as import does not go through any thread code your performance improvements are mainly useful for populate which is not a production tool.

IMO, any gain is good to take... populate may be a side tool, but I hope it's gonna be used more in the future (I use it a lot already to test some ORM stuff on large recordsets).
Furthermore, I believe there should be some places where tasks (or any other model with a creation_subtype) are created in batch and the gain could be appreciated there.

[tde-banana-odoo]

Heeee, why closing ?

[Feyensv]

Why not?
Part of it was merged already (insert_followers perf improvement) and the remaining part might as well be done again from scratch if we really want to resurrect the idea.

[tde-banana-odoo]

Snif.