#30002: Dynamic model
-------------------------------------+-------------------------------------
Reporter: temi4 | Owner: temi4
Type: Uncategorized | Status: assigned
Component: Database layer | Version: 2.1
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by temi4):
* owner: nobody => temi4
* status: new => assigned
Old description:
> I have ProjectCategoryCountPartition model
> {{{
> class ProjectCategoryCountPartition(models.Model):
>
> city_slug = models.CharField(verbose_name=_('City slug'),
> max_length=255, db_index=True)
> domain = models.CharField(verbose_name=_('Site name'),
> max_length=255)
> category_id = models.PositiveIntegerField(verbose_name=_('Category
> id'))
> name = models.CharField(verbose_name=_('Category project name'),
> max_length=255)
> count = models.PositiveIntegerField(default=0)
>
> class Meta:
> db_table = "wbtm_projects_category_partition"
>
> class DefaultMeta:
> db_table = "wbtm_projects_category_partition"
> ATTRIBUTE = {
> 'city_slug': models.CharField(verbose_name=_('City slug'),
> max_length=255, db_index=True),
> 'domain': models.CharField(verbose_name=_('Site name'),
> max_length=255),
> 'category_id':
> models.PositiveIntegerField(verbose_name=_('Category id')),
> 'name': models.CharField(verbose_name=_('Category project
> name'), max_length=255),
> 'count': models.PositiveIntegerField(default=0)
> }
>
> @classmethod
> def check_partition(cls, city_slug):
> city_slug = cls.check_city_slug(city_slug)
>
> default_db_table = cls.DefaultMeta.db_table
> new_db_table = "{}_{}".format(default_db_table, city_slug)
>
> if new_db_table in connection.introspection.table_names():
> return True
>
> return False
>
> @classmethod
> def check_city_slug(cls, city_slug):
> city_slug = city_slug.replace('-', '_')
> if not re.match('^[a-zA-Z0-9_]+?$', city_slug):
> raise Exception('Unsupported city_slug')
> return city_slug
>
> @classmethod
> def create_partition(cls, city_slug):
>
> city_slug = cls.check_city_slug(city_slug)
>
> default_db_table = cls.DefaultMeta.db_table
> new_db_table = "{}_{}".format(default_db_table, city_slug)
>
> if cls.check_partition(city_slug):
> return new_db_table
>
> queries = [
> """
> CREATE TABLE {}() INHERITS ({});
> """.format(new_db_table, default_db_table),
> ]
>
> cursor = connection.cursor()
> for query in queries:
> cursor.execute(query)
>
> return new_db_table
>
> @classmethod
> def get_city_model(cls, city_slug):
> city_slug = cls.check_city_slug(city_slug)
> model_name = city_slug.replace('_','')
>
> db_table = cls.create_partition(city_slug)
> attrs = cls.DefaultMeta.ATTRIBUTE.copy()
> attrs.update({
> '__module__': ProjectCategoryCountPartition.__module__,
> 'Meta': type(
> 'Meta',
> (),
> dict(
> # managed=False,
> db_table=db_table,
> )
> ),
> })
>
> return type("ProjectCategoryCountPartition{}".format(model_name),
> (models.Model,), attrs)
> }}}
>
> I write method:
>
> {{{
> for city in ['moskva', 'london']:
> ProjectCategoryCountPartitionModel =
> ProjectCategoryCountPartition.get_city_model(project_city.slug)
> print(ProjectCategoryCountPartitionModel.objects.filter(
> city_slug=city,
> domain='site.ru',
> category_id=1,
> ).query)
>
> data = {'name': 'Cat1', 'count': 1}
> ProjectCategoryCountPartitionModel.objects.update_or_create(
> city_slug=city,
> domain='site.ru',
> category_id=1,
> defaults=data
> )
> }}}
>
> But, Second call ProjectCategoryCountPartitionModel, return error query.
> Example:
>
> {{{
> SELECT "wbtm_projects_category_partition_london"."id",
> "wbtm_projects_category_partition_moskva"."city_slug",
> "wbtm_projects_category_partition_moskva"."domain",
> "wbtm_projects_category_partition_moskva"."category_id",
> "wbtm_projects_category_partition_moskva"."name",
> "wbtm_projects_category_partition_moskva"."count" FROM
> "wbtm_projects_category_partition_london" WHERE
> ("wbtm_projects_category_partition_moskva"."category_id" = 1 AND
> "wbtm_projects_category_partition_moskva"."city_slug" = 'london' AND
> "wbtm_projects_category_partition_moskva"."domain" = 'site.ru')
> }}}
>
> Why are the previous model fields cached in the new model?
New description:
I have ProjectCategoryCountPartition model
{{{
class ProjectCategoryCountPartition(models.Model):
city_slug = models.CharField(verbose_name=_('City slug'),
max_length=255, db_index=True)
domain = models.CharField(verbose_name=_('Site name'), max_length=255)
category_id = models.PositiveIntegerField(verbose_name=_('Category
id'))
name = models.CharField(verbose_name=_('Category project name'),
max_length=255)
count = models.PositiveIntegerField(default=0)
class Meta:
db_table = "wbtm_projects_category_partition"
class DefaultMeta:
db_table = "wbtm_projects_category_partition"
ATTRIBUTE = {
'city_slug': models.CharField(verbose_name=_('City slug'),
max_length=255, db_index=True),
'domain': models.CharField(verbose_name=_('Site name'),
max_length=255),
'category_id':
models.PositiveIntegerField(verbose_name=_('Category id')),
'name': models.CharField(verbose_name=_('Category project
name'), max_length=255),
'count': models.PositiveIntegerField(default=0)
}
@classmethod
def check_partition(cls, city_slug):
city_slug = cls.check_city_slug(city_slug)
default_db_table = cls.DefaultMeta.db_table
new_db_table = "{}_{}".format(default_db_table, city_slug)
if new_db_table in connection.introspection.table_names():
return True
return False
@classmethod
def check_city_slug(cls, city_slug):
city_slug = city_slug.replace('-', '_')
if not re.match('^[a-zA-Z0-9_]+?$', city_slug):
raise Exception('Unsupported city_slug')
return city_slug
@classmethod
def create_partition(cls, city_slug):
city_slug = cls.check_city_slug(city_slug)
default_db_table = cls.DefaultMeta.db_table
new_db_table = "{}_{}".format(default_db_table, city_slug)
if cls.check_partition(city_slug):
return new_db_table
queries = [
"""
CREATE TABLE {}() INHERITS ({});
""".format(new_db_table, default_db_table),
]
cursor = connection.cursor()
for query in queries:
cursor.execute(query)
return new_db_table
@classmethod
def get_city_model(cls, city_slug):
city_slug = cls.check_city_slug(city_slug)
model_name = city_slug.replace('_','')
db_table = cls.create_partition(city_slug)
attrs = cls.DefaultMeta.ATTRIBUTE.copy()
attrs.update({
'__module__': ProjectCategoryCountPartition.__module__,
'Meta': type(
'Meta',
(),
dict(
# managed=False,
db_table=db_table,
)
),
})
return type("ProjectCategoryCountPartition{}".format(model_name),
(models.Model,), attrs)
}}}
I write method:
{{{
for city in ['moskva', 'london']:
ProjectCategoryCountPartitionModel =
ProjectCategoryCountPartition.get_city_model(city)
print(ProjectCategoryCountPartitionModel.objects.filter(
city_slug=city,
domain='site.ru',
category_id=1,
).query)
data = {'name': 'Cat1', 'count': 1}
ProjectCategoryCountPartitionModel.objects.update_or_create(
city_slug=city,
domain='site.ru',
category_id=1,
defaults=data
)
}}}
But, Second call ProjectCategoryCountPartitionModel, return error query.
Example:
{{{
SELECT "wbtm_projects_category_partition_london"."id",
"wbtm_projects_category_partition_moskva"."city_slug",
"wbtm_projects_category_partition_moskva"."domain",
"wbtm_projects_category_partition_moskva"."category_id",
"wbtm_projects_category_partition_moskva"."name",
"wbtm_projects_category_partition_moskva"."count" FROM
"wbtm_projects_category_partition_london" WHERE
("wbtm_projects_category_partition_moskva"."category_id" = 1 AND
"wbtm_projects_category_partition_moskva"."city_slug" = 'london' AND
"wbtm_projects_category_partition_moskva"."domain" = 'site.ru')
}}}
Why are the previous model fields cached in the new model?
--
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Ticket URL: <https://code.djangoproject.com/ticket/30002#comment:1>
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