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from django.conf import settings
from django.core.cache import caches
from django.core.cache.backends.db import BaseDatabaseCache
from django.core.management.base import BaseCommand, CommandError
from django.db import (
DEFAULT_DB_ALIAS, connections, models, router, transaction,
)
from django.db.utils import DatabaseError
from django.utils.encoding import force_text
class Command(BaseCommand):
help = "Creates the tables needed to use the SQL cache backend."
requires_system_checks = False
def add_arguments(self, parser):
parser.add_argument('args', metavar='table_name', nargs='*',
help='Optional table names. Otherwise, settings.CACHES is used to '
'find cache tables.')
parser.add_argument('--database', action='store', dest='database',
default=DEFAULT_DB_ALIAS,
help='Nominates a database onto which the cache tables will be '
'installed. Defaults to the "default" database.')
def handle(self, *tablenames, **options):
db = options.get('database')
self.verbosity = int(options.get('verbosity'))
if len(tablenames):
# Legacy behavior, tablename specified as argument
for tablename in tablenames:
self.create_table(db, tablename)
else:
for cache_alias in settings.CACHES:
cache = caches[cache_alias]
if isinstance(cache, BaseDatabaseCache):
self.create_table(db, cache._table)
def create_table(self, database, tablename):
cache = BaseDatabaseCache(tablename, {})
if not router.allow_migrate(database, cache.cache_model_class):
return
connection = connections[database]
if tablename in connection.introspection.table_names():
if self.verbosity > 0:
self.stdout.write("Cache table '%s' already exists." % tablename)
return
fields = (
# "key" is a reserved word in MySQL, so use "cache_key" instead.
models.CharField(name='cache_key', max_length=255, unique=True, primary_key=True),
models.TextField(name='value'),
models.DateTimeField(name='expires', db_index=True),
)
table_output = []
index_output = []
qn = connection.ops.quote_name
for f in fields:
field_output = [qn(f.name), f.db_type(connection=connection)]
field_output.append("%sNULL" % ("NOT " if not f.null else ""))
if f.primary_key:
field_output.append("PRIMARY KEY")
elif f.unique:
field_output.append("UNIQUE")
if f.db_index:
unique = "UNIQUE " if f.unique else ""
index_output.append("CREATE %sINDEX %s ON %s (%s);" %
(unique, qn('%s_%s' % (tablename, f.name)), qn(tablename),
qn(f.name)))
table_output.append(" ".join(field_output))
full_statement = ["CREATE TABLE %s (" % qn(tablename)]
for i, line in enumerate(table_output):
full_statement.append(' %s%s' % (line, ',' if i < len(table_output) - 1 else ''))
full_statement.append(');')
with transaction.atomic(using=database,
savepoint=connection.features.can_rollback_ddl):
with connection.cursor() as curs:
try:
curs.execute("\n".join(full_statement))
except DatabaseError as e:
raise CommandError(
"Cache table '%s' could not be created.\nThe error was: %s." %
(tablename, force_text(e)))
for statement in index_output:
curs.execute(statement)
if self.verbosity > 1:
self.stdout.write("Cache table '%s' created." % tablename)
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