#26291: loaddata cannot deserialize fixtures with forward references and natural
foreign keys
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Reporter: inglesp | Owner: nobody
Type: New feature | Status: new
Component: Core | Version: 1.9
(Serialization) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by freakboy3742):
@timgraham I've left some comments on the PR about specific implementation
details, but the broad-strokes approach seems sound. Unlike PK references,
Natural keys depend on being able to issue queries on the database, so
there's no way to resolve a forward reference until the object actually
exists. This means that deferring selected objects is the only approach
that is going to work. I can't think of any situation where this will
cause a regression in behavior - it just means a subset of all fixtures
that wasn't previously loadable now will be. AFAICT, the code that Peter
has added should only be activated in the case of fixtures that can't
currently be parsed at all.
The only alternative that I can see would be to improve
`sort_dependencies` so that it only issued fixtures in a format that can
be read again. However, that doesn't improve the general case that Peter
has identified - fixtures generated by an external source.
The dependency resolution issue that Peter flags *should* (AFAIK) only
exist for natural key fixtures (for the reason identified previously), and
MySQL InnoDB data stores (because InnoDB's implementation of referential
integrity is demonstrably broken). On other data stores, forward PK
references aren't an issue.
--
Ticket URL: <https://code.djangoproject.com/ticket/26291#comment:4>
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