#25425: Enforce calling resolve_expression before as_sql on all expressions
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Reporter: jarshwah | Owner: nobody
Type: Bug | Status: new
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 |
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There are many places in the ORM that will try to compile an expression
without first having ensured it was resolved. The contract of expressions
is as follows:
{{{
resolved = expression.resolve_expression(*kwargs)
sql, params = compiler.compile(resolved)
}}}
Resolving the expression does two major things. First, it creates a copy
so that expressions can be shared without clashing with each other.
Secondly, the resolve_expression method may do necessary validation or
extra query work.
There are a few known places where expression like objects are used
without first being resolved.
- Most `Where` nodes are not resolved correctly (anywhere where self.where
or self.query.where is compiled)
- SQLUpdateCompiler
- SQLDeleteCompiler
- django.db.models.lookups.Lookup
- django.db.models.related_lookups.RelatedIn
I wonder if we should consider enforcing this at the code level. Refuse to
compile the expression unless it has been resolved first. A naive way of
doing this would be to maintain a `resolved` boolean flag, and switch it
to `True` when resolved. The `as_sql` method could then error if the
expression has not been resolved.
--
Ticket URL: <https://code.djangoproject.com/ticket/25425>
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