Feature Request: Allow passing no-op filters to QuerySet's bulk_update() when updating tables with partitions

[opqpop]

Hi, I'd like to pass additional partition columns into the filters for a QuerySet's bulk_update(). These would be no-op filters solely for the DB to understand from the query to lock rows in a single partition vs all partitions. 

Ex: I'd add "orig_city_id = 52" into this pk filter that bulk_update uses, because my table is partitioned on orig_city_id and passing the partition filter helps scale up when updating a lot of records: https://github.com/django/django/blob/d8c90d4c22cb218f1c170eba086c53d3dff7fbc0/django/db/models/query.py#L569

What are folks thoughts on this feature request? 

Currently I copy pasted bulk_update and tweaked it with a simple change to work (https://snippi.com/s/55qlpbn). Was wondering if this makes sense to add to Django for everyone.

Motivation for this change:

http://www.databasesoup.com/2012/06/postgresqlconf-maxlockspertransaction.html, describing how UPDATES on tables with lots of partitions without the partition column in the WHERE clauses causes DB to lock too many rows and eventually get OOM issues 

[Adam Johnson]

It should already work to do `Model.objects.filter(...).bulk_update(...)` , no?

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[opqpop]

Wow thanks so much Adam. I just verified that doing the filter before bulk_update indeed works. 

I didn't realize I could just filter it before doing the bulk_update and it would carry over with the pk filter that gets added in bulk_update. I will have to brush up on understanding Querysets better.

Thanks again!