#29037: Add a bulk_update method to models
-------------------------------------+-------------------------------------
Reporter: Tom | Owner: nobody
Forbes |
Type: New | Status: new
feature |
Component: Database | Version: master
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
Currently it's not easily or neatly possible to update multiple rows with
differing values using the ORM. Most people who need to update a number of
models with a value that's distinct to each model need to issue N queries.
This is akin to the situation that lead to the addition of bulk_create.
Updating multiple rows with differing values in a single query is indeed
possible in SQL, and Postgres has some specific syntax for it[1]. Other
databases can use a CASE/WHEN:
{{{#!python
SomeModel.object.update(
some_field=Case(
When(id=1, then=Value('Field value for ID=1')),
When(id=2, then=Value('Field value for ID=2'))
)
)
}}}
This isn't particularly elegant and cannot take advantage of specific DB
features (like pg UPDATE FROM), and batching is hard. An API similar to
bulk_create would be nice:
{{{#!python
SomeModel.objects.bulk_update(list_of_models, batch_size=100)
}}}
There is some prior art in the django-bulk-update package[2], which has
some impressive performance numbers in it's readme.
1. https://stackoverflow.com/questions/18797608/update-multiple-rows-in-
same-query-using-postgresql
2. https://github.com/aykut/django-bulk-update
--
Ticket URL: <https://code.djangoproject.com/ticket/29037>
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