#36815: Avoid unnecessary prepare_value calls when inserting db_defaults
-------------------------------------+-------------------------------------
Reporter: Adam Sołtysik | Type:
| Cleanup/optimization
Status: new | Component: Database
| layer (models, ORM)
Version: 6.0 | Severity: Normal
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
In `SQLInsertCompiler.as_sql`, it looks like `prepare_value` is
unnecessarily called for each `DatabaseDefault` value on every inserted
object. These calls are quite expensive (as they enter the `if
hasattr(value, "resolve_expression")` branch) and waste a lot of time when
using `bulk_create`.
I've written a potential patch and a simple benchmark:
https://github.com/adamsol/django/commit/d6f275c8960988c92a9da5eb323b6bd6fc7717cb.
The benchmark runs 2x faster with the fix, even though there's only one
field with `db_default` in that model. The difference may become larger
with more fields.
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Ticket URL: <https://code.djangoproject.com/ticket/36815>
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