forked from CGM_Public/pretix_original
97 lines
2.9 KiB
Python
97 lines
2.9 KiB
Python
import contextlib
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from django.db import transaction
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from django.db.models import Aggregate
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from django.db.models.expressions import OrderBy
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class DummyRollbackException(Exception):
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pass
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@contextlib.contextmanager
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def rolledback_transaction():
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"""
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This context manager runs your code in a database transaction that will be rolled back in the end.
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This can come in handy to simulate the effects of a database operation that you do not actually
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want to perform.
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Note that rollbacks are a very slow operation on most database backends. Also, long-running
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transactions can slow down other operations currently running and you should not use this
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in a place that is called frequently.
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"""
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try:
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with transaction.atomic():
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yield
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raise DummyRollbackException()
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except DummyRollbackException:
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pass
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else:
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raise Exception('Invalid state, should have rolled back.')
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@contextlib.contextmanager
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def casual_reads():
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"""
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Kept for backwards compatibility.
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"""
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yield
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class FixedOrderBy(OrderBy):
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# Workaround for https://code.djangoproject.com/ticket/28848
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template = '%(expression)s %(ordering)s'
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def as_sql(self, compiler, connection, template=None, **extra_context):
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if not template:
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if self.nulls_last:
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template = '%s NULLS LAST' % self.template
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elif self.nulls_first:
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template = '%s NULLS FIRST' % self.template
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connection.ops.check_expression_support(self)
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expression_sql, params = compiler.compile(self.expression)
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placeholders = {
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'expression': expression_sql,
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'ordering': 'DESC' if self.descending else 'ASC',
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}
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placeholders.update(extra_context)
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template = template or self.template
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params = params * template.count('%(expression)s')
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return (template % placeholders).rstrip(), params
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class GroupConcat(Aggregate):
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function = 'group_concat'
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template = '%(function)s(%(field)s, "%(separator)s")'
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def __init__(self, *expressions, **extra):
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if 'separator' not in extra:
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# For PostgreSQL separator is an obligatory
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extra.update({'separator': ','})
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super().__init__(*expressions, **extra)
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def as_postgresql(self, compiler, connection):
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return super().as_sql(
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compiler, connection,
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function='string_agg',
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template="%(function)s(%(field)s::text, '%(separator)s')",
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)
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class ReplicaRouter:
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def db_for_read(self, model, **hints):
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return 'default'
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def db_for_write(self, model, **hints):
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return 'default'
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def allow_relation(self, obj1, obj2, **hints):
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db_list = ('default', 'replica')
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if obj1._state.db in db_list and obj2._state.db in db_list:
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return True
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return None
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def allow_migrate(self, db, app_label, model_name=None, **hintrs):
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return True
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