Re: [Django] #35438: Failed to insert an model instance into db that utilizes a UUID as its primary key and incorporates a GeneratedField.

[Django]

#35438: Failed to insert an model instance into db that utilizes a UUID as its
primary key and incorporates a GeneratedField.
---+--
 Reporter:  长孙弘奕   |Owner:  nobody
 Type:  Uncategorized  |   Status:  closed
Component:  Uncategorized  |  Version:  5.0
 Severity:  Normal |   Resolution:  needsinfo
 Keywords: | Triage Stage:  Unreviewed
Has patch:  1  |  Needs documentation:  0
  Needs tests:  0  |  Patch needs improvement:  0
Easy pickings:  0  |UI/UX:  0
---+--
Changes (by Sarah Boyce):

 * resolution:   => needsinfo
 * status:  new => closed

Comment:

 Hi 长孙弘奕, thank you for the report and patch.
 I'm struggling to see exactly what is happening here. Can you perhaps
 share your model, fixture and error?
 If you provide a regression test to the patch that will also be really
 helpful to be able to see the issue
-- 
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

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[Django] #35438: Failed to insert an model instance into db that utilizes a UUID as its primary key and incorporates a GeneratedField.

[Django]

#35438: Failed to insert an model instance into db that utilizes a UUID as its
primary key and incorporates a GeneratedField.
-+
   Reporter:  长孙弘奕   |  Owner:  nobody
   Type:  Uncategorized  | Status:  new
  Component:  Uncategorized  |Version:  5.0
   Severity:  Normal |   Keywords:
   Triage Stage:  Unreviewed |  Has patch:  1
Needs documentation:  0  |Needs tests:  0
Patch needs improvement:  0  |  Easy pickings:  0
  UI/UX:  0  |
-+
 I have defined a model that employs a UUIDField as its primary key,
 accompanied by a JSONField and several GeneratedFields, which are intended
 for indexing the JSONFields. However, when attempting to load data via
 loaddata from a JSON fixture, the process fails during the execution of
 the execute_sql method within django/db/models/SQL/compiler.py. The
 problematic code snippet is as follows:

 {{{
 def execute_sql(self, returning_fields=None):
 
 if not self.returning_fields:
 return []

 else:
 cols = [opts.pk.get_col(opts.db_table)]
 rows = [
 (
 self.connection.ops.last_insert_id(
 cursor,
 opts.db_table,
 opts.pk.column,
 ),
 )
 ]
 converters = self.get_converters(cols)
 if converters:
 rows = list(self.apply_converters(rows, converters))
 return rows
 }}}


 Here, returning_fields comprises GeneratedFields, thereby preventing the
 method from directly returning an empty list at the outset of its logical
 execution. Moreover, since the model's primary key is not an
 AUTO_INCREMENT column (it's a UUID), last_insert_id() erroneously returns
 0. This subsequently triggers an error within self.apply_converters(rows,
 converters) as it attempts to treat 0 as a UUID.

 To address this issue, the else block logic requires adjustment to
 accommodate the presence of GeneratedField. Alternatively, within
 django/db/models/base.py's _save_table method, one could exclude
 GeneratedField from returning_fields. A modified approach might resemble:


 {{{
#Original: returning_fields = meta.db_returning_fields
 returning_fields = [ f for f in meta.db_returning_fields if
 not f.generated]
 results = self._do_insert(
 cls._base_manager, using, fields, returning_fields, raw
 )
 if results:
 for value, field in zip(results[0], returning_fields):
 setattr(self, field.attname, value)
 return updated
 }}}

 This adjusted strategy has proven effective in my project, successfully
 circumventing the aforementioned issues without introducing new problems.
-- 
Ticket URL: 
Django 
The Web framework for perfectionists with deadlines.

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