django1/django/db/backends/__init__.py

219 lines
6.9 KiB
Python

try:
# Only exists in Python 2.4+
from threading import local
except ImportError:
# Import copy of _thread_local.py from Python 2.4
from django.utils._threading_local import local
class BaseDatabaseWrapper(local):
"""
Represents a database connection.
"""
ops = None
def __init__(self, **kwargs):
self.connection = None
self.queries = []
self.options = kwargs
def _commit(self):
if self.connection is not None:
return self.connection.commit()
def _rollback(self):
if self.connection is not None:
return self.connection.rollback()
def close(self):
if self.connection is not None:
self.connection.close()
self.connection = None
def cursor(self):
from django.conf import settings
cursor = self._cursor(settings)
if settings.DEBUG:
return self.make_debug_cursor(cursor)
return cursor
def make_debug_cursor(self, cursor):
from django.db.backends import util
return util.CursorDebugWrapper(cursor, self)
class BaseDatabaseFeatures(object):
allows_group_by_ordinal = True
allows_unique_and_pk = True
autoindexes_primary_keys = True
needs_datetime_string_cast = True
needs_upper_for_iops = False
supports_constraints = True
supports_tablespaces = False
uses_case_insensitive_names = False
uses_custom_queryset = False
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.
"""
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 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()
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()
def datetime_cast_sql(self):
"""
Returns the SQL necessary to cast a datetime value so that it will be
retrieved as a Python datetime object instead of a string.
This SQL should include a '%s' in place of the field's name. This
method should return None if no casting is necessary.
"""
return None
def deferrable_sql(self):
"""
Returns the SQL necessary to make a constraint "initially deferred"
during a CREATE TABLE statement.
"""
return ''
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 field_cast_sql(self, db_type):
"""
Given a column type (e.g. 'BLOB', 'VARCHAR'), 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 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_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 limit_offset_sql(self, limit, offset=None):
"""
Returns a LIMIT/OFFSET SQL clause, given a limit and optional offset.
"""
# 'LIMIT 40 OFFSET 20'
sql = "LIMIT %s" % limit
if offset and offset != 0:
sql += " OFFSET %s" % offset
return sql
def max_name_length(self):
"""
Returns the maximum length of table and column names, or None if there
is no limit.
"""
return None
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 query_set_class(self, DefaultQuerySet):
"""
Given the default QuerySet class, returns a custom QuerySet class
to use for this backend. Returns None if a custom QuerySet isn't used.
See also BaseDatabaseFeatures.uses_custom_queryset, which regulates
whether this method is called at all.
"""
return None
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()
def random_function_sql(self):
"""
Returns a SQL expression that returns a random value.
"""
return 'RANDOM()'
def sql_flush(self, style, tables, sequences):
"""
Returns a list of SQL statements required to remove all data from
the given database tables (without actually removing the tables
themselves).
The `style` argument is a Style object as returned by either
color_style() or no_style() in django.core.management.color.
"""
raise NotImplementedError()
def sequence_reset_sql(self, style, model_list):
"""
Returns a list of the SQL statements required to reset sequences for
the given models.
The `style` argument is a Style object as returned by either
color_style() or no_style() in django.core.management.color.
"""
return [] # No sequence reset required by default.
def start_transaction_sql(self):
"""
Returns the SQL statement required to start a transaction.
"""
return "BEGIN;"
def tablespace_sql(self, tablespace, inline=False):
"""
Returns the tablespace SQL, or None if the backend doesn't use
tablespaces.
"""
return None