import datetime
import decimal
import warnings
from importlib import import_module
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.db.backends import utils
from django.utils import six, timezone
from django.utils.dateparse import parse_duration
from django.utils.deprecation import RemovedInDjango20Warning
from django.utils.encoding import force_text
class BaseDatabaseOperations(object):
"""
This class encapsulates all backend-specific differences, such as the way
a backend performs ordering or calculates the ID of a recently-inserted
row.
"""
compiler_module = "django.db.models.sql.compiler"
# Integer field safe ranges by `internal_type` as documented
# in docs/ref/models/fields.txt.
integer_field_ranges = {
'SmallIntegerField': (-32768, 32767),
'IntegerField': (-2147483648, 2147483647),
'BigIntegerField': (-9223372036854775808, 9223372036854775807),
'PositiveSmallIntegerField': (0, 32767),
'PositiveIntegerField': (0, 2147483647),
}
def __init__(self, connection):
self.connection = connection
self._cache = None
def autoinc_sql(self, table, column):
"""
Returns any SQL needed to support auto-incrementing primary keys, or
None if no SQL is necessary.
This SQL is executed when a table is created.
"""
return None
def bulk_batch_size(self, fields, objs):
"""
Returns the maximum allowed batch size for the backend. The fields
are the fields going to be inserted in the batch, the objs contains
all the objects to be inserted.
"""
return len(objs)
def cache_key_culling_sql(self):
"""
Returns an SQL query that retrieves the first cache key greater than the
n smallest.
This is used by the 'db' cache backend to determine where to start
culling.
"""
return "SELECT cache_key FROM %s ORDER BY cache_key LIMIT 1 OFFSET %%s"
def unification_cast_sql(self, output_field):
"""
Given a field instance, returns the SQL necessary to cast the result of
a union to that type. Note that the resulting string should contain a
'%s' placeholder for the expression being cast.
"""
return '%s'
def date_extract_sql(self, lookup_type, field_name):
"""
Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
extracts a value from the given date field field_name.
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_extract_sql() method')
def date_interval_sql(self, timedelta):
"""
Implements the date interval functionality for expressions
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_interval_sql() method')
def date_trunc_sql(self, lookup_type, field_name):
"""
Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
truncates the given date field field_name to a date object with only
the given specificity.
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetrunc_sql() method')
def datetime_cast_date_sql(self, field_name, tzname):
"""
Returns the SQL necessary to cast a datetime value to date value.
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_cast_date() method')
def datetime_extract_sql(self, lookup_type, field_name, tzname):
"""
Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
'second', returns the SQL that extracts a value from the given
datetime field field_name, and a tuple of parameters.
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_extract_sql() method')
def datetime_trunc_sql(self, lookup_type, field_name, tzname):
"""
Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
'second', returns the SQL that truncates the given datetime field
field_name to a datetime object with only the given specificity, and
a tuple of parameters.
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_trunk_sql() method')
def time_extract_sql(self, lookup_type, field_name):
"""
Given a lookup_type of 'hour', 'minute' or 'second', returns the SQL
that extracts a value from the given time field field_name.
"""
return self.date_extract_sql(lookup_type, field_name)
def deferrable_sql(self):
"""
Returns the SQL necessary to make a constraint "initially deferred"
during a CREATE TABLE statement.
"""
return ''
def distinct_sql(self, fields):
"""
Returns an SQL DISTINCT clause which removes duplicate rows from the
result set. If any fields are given, only the given fields are being
checked for duplicates.
"""
if fields:
raise NotImplementedError('DISTINCT ON fields is not supported by this database backend')
else:
return 'DISTINCT'
def drop_foreignkey_sql(self):
"""
Returns the SQL command that drops a foreign key.
"""
return "DROP CONSTRAINT"
def drop_sequence_sql(self, table):
"""
Returns any SQL necessary to drop the sequence for the given table.
Returns None if no SQL is necessary.
"""
return None
def fetch_returned_insert_id(self, cursor):
"""
Given a cursor object that has just performed an INSERT...RETURNING
statement into a table that has an auto-incrementing ID, returns the
newly created ID.
"""
return cursor.fetchone()[0]
def field_cast_sql(self, db_type, internal_type):
"""
Given a column type (e.g. 'BLOB', 'VARCHAR'), and an internal type
(e.g. 'GenericIPAddressField'), returns the SQL necessary to cast it
before using it in a WHERE statement. Note that the resulting string
should contain a '%s' placeholder for the column being searched against.
"""
return '%s'
def force_no_ordering(self):
"""
Returns a list used in the "ORDER BY" clause to force no ordering at
all. Returning an empty list means that nothing will be included in the
ordering.
"""
return []
def for_update_sql(self, nowait=False):
"""
Returns the FOR UPDATE SQL clause to lock rows for an update operation.
"""
if nowait:
return 'FOR UPDATE NOWAIT'
else:
return 'FOR UPDATE'
def fulltext_search_sql(self, field_name):
"""
Returns the SQL WHERE clause to use in order to perform a full-text
search of the given field_name. Note that the resulting string should
contain a '%s' placeholder for the value being searched against.
"""
raise NotImplementedError('Full-text search is not implemented for this database backend')
def last_executed_query(self, cursor, sql, params):
"""
Returns a string of the query last executed by the given cursor, with
placeholders replaced with actual values.
`sql` is the raw query containing placeholders, and `params` is the
sequence of parameters. These are used by default, but this method
exists for database backends to provide a better implementation
according to their own quoting schemes.
"""
# Convert params to contain Unicode values.
to_unicode = lambda s: force_text(s, strings_only=True, errors='replace')
if isinstance(params, (list, tuple)):
u_params = tuple(to_unicode(val) for val in params)
elif params is None:
u_params = ()
else:
u_params = {to_unicode(k): to_unicode(v) for k, v in params.items()}
return six.text_type("QUERY = %r - PARAMS = %r") % (sql, u_params)
def last_insert_id(self, cursor, table_name, pk_name):
"""
Given a cursor object that has just performed an INSERT statement into
a table that has an auto-incrementing ID, returns the newly created ID.
This method also receives the table name and the name of the primary-key
column.
"""
return cursor.lastrowid
def lookup_cast(self, lookup_type, internal_type=None):
"""
Returns the string to use in a query when performing lookups
("contains", "like", etc.). The resulting string should contain a '%s'
placeholder for the column being searched against.
"""
return "%s"
def max_in_list_size(self):
"""
Returns the maximum number of items that can be passed in a single 'IN'
list condition, or None if the backend does not impose a limit.
"""
return None
def max_name_length(self):
"""
Returns the maximum length of table and column names, or None if there
is no limit.
"""
return None
def no_limit_value(self):
"""
Returns the value to use for the LIMIT when we are wanting "LIMIT
infinity". Returns None if the limit clause can be omitted in this case.
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a no_limit_value() method')
def pk_default_value(self):
"""
Returns the value to use during an INSERT statement to specify that
the field should use its default value.
"""
return 'DEFAULT'
def prepare_sql_script(self, sql):
"""
Takes an SQL script that may contain multiple lines and returns a list
of statements to feed to successive cursor.execute() calls.
Since few databases are able to process raw SQL scripts in a single
cursor.execute() call and PEP 249 doesn't talk about this use case,
the default implementation is conservative.
"""
try:
import sqlparse
except ImportError:
raise ImproperlyConfigured(
"sqlparse is required if you don't split your SQL "
"statements manually."
)
else:
return [sqlparse.format(statement, strip_comments=True)
for statement in sqlparse.split(sql) if statement]
def process_clob(self, value):
"""
Returns the value of a CLOB column, for backends that return a locator
object that requires additional processing.
"""
return value
def return_insert_id(self):
"""
For backends that support returning the last insert ID as part
of an insert query, this method returns the SQL and params to
append to the INSERT query. The returned fragment should
contain a format string to hold the appropriate column.
"""
pass
def compiler(self, compiler_name):
"""
Returns the SQLCompiler class corresponding to the given name,
in the namespace corresponding to the `compiler_module` attribute
on this backend.
"""
if self._cache is None:
self._cache = import_module(self.compiler_module)
return getattr(self._cache, compiler_name)
def quote_name(self, name):
"""
Returns a quoted version of the given table, index or column name. Does
not quote the given name if it's already been quoted.
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a quote_name() method')
def random_function_sql(self):
"""
Returns an SQL expression that returns a random value.
"""
return 'RANDOM()'
def regex_lookup(self, lookup_type):
"""
Returns the string to use in a query when performing regular expression
lookups (using "regex" or "iregex"). The resulting string should
contain a '%s' placeholder for the column being searched against.
If the feature is not supported (or part of it is not supported), a
NotImplementedError exception can be raised.
"""
raise NotImplementedError('subclasses of BaseDatabaseOperations may require a regex_lookup() method')
def savepoint_create_sql(self, sid):
"""
Returns the SQL for starting a new savepoint. Only required if the
"uses_savepoints" feature is True. The "sid" parameter is a string
for the savepoint id.
"""
return "SAVEPOINT %s" % self.quote_name(sid)
def savepoint_commit_sql(self, sid):
"""
Returns the SQL for committing the given savepoint.
"""
return "RELEASE SAVEPOINT %s" % self.quote_name(sid)
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