#28704: update_or_create() calls select_for_update(), which locks database row
-------------------------------------+-------------------------------------
Reporter: Rafal Radulski | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Tomer Chachamu):
I'm assuming you're passing something in `defaults`, right?
`update_or_create` currently calls `Model.save` and you are suggesting it
should call `QuerySet.update` instead. Both of them send `UPDATE` SQL
statements to the database. That will create a row-level lock. In
Postgres, the lock level is either `FOR UPDATE` or `FOR NO KEY UPDATE`,
see https://www.postgresql.org/docs/9.6/static/explicit-locking.html
#LOCKING-ROWS.
But, neither of these locks will block an ordinary `SELECT` statement like
the `.get()` in the second transaction.
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Ticket URL: <https://code.djangoproject.com/ticket/28704#comment:1>
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