#35977: Serializing ManyToMany fields produces inconsistent order (on Postgres)
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Reporter: Alexander Todorov | Owner: (none)
Type: New feature | Status: closed
Component: Core | Version: 5.1
(Serialization) |
Severity: Normal | Resolution: wontfix
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 Simon Charette):
Agree with Sarah here!
The lack of ordering consistency when retrieving objects from the database
**without an explicit ordering** is not specified is not a Postgres or
serialization specific problem.
When no `ORDERY BY` is specified the database can choose to return values
in the order it wants which is usually the fastest one. In the case of
database like MySQL that usually means by primary key as that's how the
data is clustered/organized on disk while on Postgres it depends on
multiple factors.
The patch you are proposing would be backward incompatible for two reasons
1. It would change the order of serialized data for models that explicitly
opted-in into a particular order
2. The systematic order by primary key could slow down serialization of
projects that don't care about ordering of data
In other words, database don't return data in a stable order unless you
explicitly ask for it and Django provides a way to do so through through
`Meta.ordering` and manager overrides `order_by`.
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Ticket URL: <https://code.djangoproject.com/ticket/35977#comment:3>
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