#28857: Cast function may generate invalid SQL on PostgreSQL for complex
expressions
-------------------------------------+-------------------------------------
Reporter: Jurica Železnjak | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.11
(models, ORM) |
Severity: Normal | Resolution:
Keywords: postgres,orm | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 1 | UI/UX: 0
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Comment (by Jurica Železnjak):
Replying to [comment:3 Tim Graham]:
> It looks like parentheses could also be added to
`ObjectAtPath.template`. Can you reproduce the problem with any of the
built-in database functions? With either solution, it seems like
unnecessary parenthesis would be present in some cases. It would be nice
to avoid that if possible.
True, but that's not the point. The point is that with the default
implementation of Cast function it would work fine always, but with the
overridden postgresql-specific it does not.
ObjectAtPath does its own thing like it should - fetches a value by key
from JSON field.
{{{
def as_postgresql(self, compiler, connection):
# CAST would be valid too, but the :: shortcut syntax is more
readable.
return self.as_sql(compiler, connection,
template='%(expressions)s::%(db_type)s')
}}}
But the reasoning for the built-in shortcut postgresql-specific method is
that it would be more readable - while that's true - it leads to the
mentioned problem.
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Ticket URL: <https://code.djangoproject.com/ticket/28857#comment:4>
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