594 lines
22 KiB
Python
594 lines
22 KiB
Python
import datetime
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import decimal
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import warnings
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from importlib import import_module
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from django.conf import settings
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from django.core.exceptions import ImproperlyConfigured
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from django.db.backends import utils
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from django.utils import six, timezone
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from django.utils.dateparse import parse_duration
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from django.utils.deprecation import RemovedInDjango21Warning
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from django.utils.encoding import force_text
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class BaseDatabaseOperations(object):
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"""
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This class encapsulates all backend-specific differences, such as the way
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a backend performs ordering or calculates the ID of a recently-inserted
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row.
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"""
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compiler_module = "django.db.models.sql.compiler"
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# Integer field safe ranges by `internal_type` as documented
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# in docs/ref/models/fields.txt.
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integer_field_ranges = {
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'SmallIntegerField': (-32768, 32767),
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'IntegerField': (-2147483648, 2147483647),
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'BigIntegerField': (-9223372036854775808, 9223372036854775807),
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'PositiveSmallIntegerField': (0, 32767),
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'PositiveIntegerField': (0, 2147483647),
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}
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def __init__(self, connection):
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self.connection = connection
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self._cache = None
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def autoinc_sql(self, table, column):
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"""
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Returns any SQL needed to support auto-incrementing primary keys, or
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None if no SQL is necessary.
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This SQL is executed when a table is created.
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"""
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return None
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def bulk_batch_size(self, fields, objs):
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"""
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Returns the maximum allowed batch size for the backend. The fields
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are the fields going to be inserted in the batch, the objs contains
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all the objects to be inserted.
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"""
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return len(objs)
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def cache_key_culling_sql(self):
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"""
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Returns an SQL query that retrieves the first cache key greater than the
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n smallest.
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This is used by the 'db' cache backend to determine where to start
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culling.
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"""
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return "SELECT cache_key FROM %s ORDER BY cache_key LIMIT 1 OFFSET %%s"
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def unification_cast_sql(self, output_field):
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"""
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Given a field instance, returns the SQL necessary to cast the result of
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a union to that type. Note that the resulting string should contain a
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'%s' placeholder for the expression being cast.
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"""
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return '%s'
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def date_extract_sql(self, lookup_type, field_name):
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"""
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Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
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extracts a value from the given date field field_name.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_extract_sql() method')
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def date_interval_sql(self, timedelta):
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"""
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Implements the date interval functionality for expressions
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a date_interval_sql() method')
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def date_trunc_sql(self, lookup_type, field_name):
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"""
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Given a lookup_type of 'year', 'month' or 'day', returns the SQL that
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truncates the given date field field_name to a date object with only
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the given specificity.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetrunc_sql() method')
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def datetime_cast_sql(self):
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"""
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Returns the SQL necessary to cast a datetime value so that it will be
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retrieved as a Python datetime object instead of a string.
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This SQL should include a '%s' in place of the field's name.
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"""
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return "%s"
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def datetime_cast_date_sql(self, field_name, tzname):
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"""
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Returns the SQL necessary to cast a datetime value to date value.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_cast_date() method')
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def datetime_extract_sql(self, lookup_type, field_name, tzname):
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"""
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Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
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'second', returns the SQL that extracts a value from the given
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datetime field field_name, and a tuple of parameters.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_extract_sql() method')
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def datetime_trunc_sql(self, lookup_type, field_name, tzname):
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"""
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Given a lookup_type of 'year', 'month', 'day', 'hour', 'minute' or
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'second', returns the SQL that truncates the given datetime field
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field_name to a datetime object with only the given specificity, and
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a tuple of parameters.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a datetime_trunk_sql() method')
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def deferrable_sql(self):
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"""
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Returns the SQL necessary to make a constraint "initially deferred"
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during a CREATE TABLE statement.
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"""
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return ''
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def distinct_sql(self, fields):
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"""
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Returns an SQL DISTINCT clause which removes duplicate rows from the
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result set. If any fields are given, only the given fields are being
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checked for duplicates.
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"""
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if fields:
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raise NotImplementedError('DISTINCT ON fields is not supported by this database backend')
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else:
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return 'DISTINCT'
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def drop_foreignkey_sql(self):
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"""
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Returns the SQL command that drops a foreign key.
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"""
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return "DROP CONSTRAINT"
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def drop_sequence_sql(self, table):
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"""
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Returns any SQL necessary to drop the sequence for the given table.
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Returns None if no SQL is necessary.
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"""
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return None
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def fetch_returned_insert_id(self, cursor):
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"""
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Given a cursor object that has just performed an INSERT...RETURNING
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statement into a table that has an auto-incrementing ID, returns the
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newly created ID.
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"""
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return cursor.fetchone()[0]
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def field_cast_sql(self, db_type, internal_type):
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"""
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Given a column type (e.g. 'BLOB', 'VARCHAR'), and an internal type
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(e.g. 'GenericIPAddressField'), returns the SQL necessary to cast it
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before using it in a WHERE statement. Note that the resulting string
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should contain a '%s' placeholder for the column being searched against.
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"""
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return '%s'
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def force_no_ordering(self):
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"""
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Returns a list used in the "ORDER BY" clause to force no ordering at
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all. Returning an empty list means that nothing will be included in the
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ordering.
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"""
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return []
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def for_update_sql(self, nowait=False):
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"""
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Returns the FOR UPDATE SQL clause to lock rows for an update operation.
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"""
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if nowait:
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return 'FOR UPDATE NOWAIT'
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else:
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return 'FOR UPDATE'
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def fulltext_search_sql(self, field_name):
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"""
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Returns the SQL WHERE clause to use in order to perform a full-text
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search of the given field_name. Note that the resulting string should
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contain a '%s' placeholder for the value being searched against.
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"""
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raise NotImplementedError('Full-text search is not implemented for this database backend')
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def last_executed_query(self, cursor, sql, params):
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"""
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Returns a string of the query last executed by the given cursor, with
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placeholders replaced with actual values.
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`sql` is the raw query containing placeholders, and `params` is the
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sequence of parameters. These are used by default, but this method
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exists for database backends to provide a better implementation
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according to their own quoting schemes.
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"""
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# Convert params to contain Unicode values.
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to_unicode = lambda s: force_text(s, strings_only=True, errors='replace')
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if isinstance(params, (list, tuple)):
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u_params = tuple(to_unicode(val) for val in params)
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elif params is None:
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u_params = ()
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else:
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u_params = {to_unicode(k): to_unicode(v) for k, v in params.items()}
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return six.text_type("QUERY = %r - PARAMS = %r") % (sql, u_params)
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def last_insert_id(self, cursor, table_name, pk_name):
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"""
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Given a cursor object that has just performed an INSERT statement into
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a table that has an auto-incrementing ID, returns the newly created ID.
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This method also receives the table name and the name of the primary-key
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column.
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"""
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return cursor.lastrowid
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def lookup_cast(self, lookup_type, internal_type=None):
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"""
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Returns the string to use in a query when performing lookups
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("contains", "like", etc). The resulting string should contain a '%s'
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placeholder for the column being searched against.
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"""
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return "%s"
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def max_in_list_size(self):
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"""
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Returns the maximum number of items that can be passed in a single 'IN'
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list condition, or None if the backend does not impose a limit.
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"""
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return None
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def max_name_length(self):
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"""
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Returns the maximum length of table and column names, or None if there
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is no limit.
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"""
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return None
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def no_limit_value(self):
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"""
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Returns the value to use for the LIMIT when we are wanting "LIMIT
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infinity". Returns None if the limit clause can be omitted in this case.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a no_limit_value() method')
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def pk_default_value(self):
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"""
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Returns the value to use during an INSERT statement to specify that
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the field should use its default value.
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"""
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return 'DEFAULT'
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def prepare_sql_script(self, sql):
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"""
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Takes a SQL script that may contain multiple lines and returns a list
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of statements to feed to successive cursor.execute() calls.
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Since few databases are able to process raw SQL scripts in a single
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cursor.execute() call and PEP 249 doesn't talk about this use case,
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the default implementation is conservative.
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"""
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try:
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import sqlparse
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except ImportError:
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raise ImproperlyConfigured(
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"sqlparse is required if you don't split your SQL "
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"statements manually."
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)
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else:
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return [sqlparse.format(statement, strip_comments=True)
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for statement in sqlparse.split(sql) if statement]
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def process_clob(self, value):
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"""
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Returns the value of a CLOB column, for backends that return a locator
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object that requires additional processing.
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"""
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return value
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def return_insert_id(self):
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"""
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For backends that support returning the last insert ID as part
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of an insert query, this method returns the SQL and params to
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append to the INSERT query. The returned fragment should
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contain a format string to hold the appropriate column.
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"""
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pass
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def compiler(self, compiler_name):
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"""
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Returns the SQLCompiler class corresponding to the given name,
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in the namespace corresponding to the `compiler_module` attribute
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on this backend.
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"""
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if self._cache is None:
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self._cache = import_module(self.compiler_module)
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return getattr(self._cache, compiler_name)
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def quote_name(self, name):
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"""
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Returns a quoted version of the given table, index or column name. Does
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not quote the given name if it's already been quoted.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a quote_name() method')
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def random_function_sql(self):
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"""
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Returns an SQL expression that returns a random value.
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"""
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return 'RANDOM()'
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def regex_lookup(self, lookup_type):
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"""
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Returns the string to use in a query when performing regular expression
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lookups (using "regex" or "iregex"). The resulting string should
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contain a '%s' placeholder for the column being searched against.
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If the feature is not supported (or part of it is not supported), a
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NotImplementedError exception can be raised.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations may require a regex_lookup() method')
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def savepoint_create_sql(self, sid):
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"""
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Returns the SQL for starting a new savepoint. Only required if the
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"uses_savepoints" feature is True. The "sid" parameter is a string
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for the savepoint id.
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"""
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return "SAVEPOINT %s" % self.quote_name(sid)
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def savepoint_commit_sql(self, sid):
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"""
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Returns the SQL for committing the given savepoint.
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"""
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return "RELEASE SAVEPOINT %s" % self.quote_name(sid)
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def savepoint_rollback_sql(self, sid):
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"""
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Returns the SQL for rolling back the given savepoint.
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"""
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return "ROLLBACK TO SAVEPOINT %s" % self.quote_name(sid)
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def set_time_zone_sql(self):
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"""
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Returns the SQL that will set the connection's time zone.
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Returns '' if the backend doesn't support time zones.
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"""
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return ''
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def sql_flush(self, style, tables, sequences, allow_cascade=False):
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"""
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Returns a list of SQL statements required to remove all data from
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the given database tables (without actually removing the tables
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themselves).
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The returned value also includes SQL statements required to reset DB
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sequences passed in :param sequences:.
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The `style` argument is a Style object as returned by either
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color_style() or no_style() in django.core.management.color.
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The `allow_cascade` argument determines whether truncation may cascade
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to tables with foreign keys pointing the tables being truncated.
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PostgreSQL requires a cascade even if these tables are empty.
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"""
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raise NotImplementedError('subclasses of BaseDatabaseOperations must provide a sql_flush() method')
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def sequence_reset_by_name_sql(self, style, sequences):
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"""
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Returns a list of the SQL statements required to reset sequences
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passed in :param sequences:.
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The `style` argument is a Style object as returned by either
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color_style() or no_style() in django.core.management.color.
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"""
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return []
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def sequence_reset_sql(self, style, model_list):
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"""
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Returns a list of the SQL statements required to reset sequences for
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the given models.
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The `style` argument is a Style object as returned by either
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color_style() or no_style() in django.core.management.color.
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"""
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return [] # No sequence reset required by default.
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def start_transaction_sql(self):
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"""
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Returns the SQL statement required to start a transaction.
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"""
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return "BEGIN;"
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def end_transaction_sql(self, success=True):
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"""
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Returns the SQL statement required to end a transaction.
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"""
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if not success:
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return "ROLLBACK;"
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return "COMMIT;"
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def tablespace_sql(self, tablespace, inline=False):
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"""
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Returns the SQL that will be used in a query to define the tablespace.
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Returns '' if the backend doesn't support tablespaces.
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If inline is True, the SQL is appended to a row; otherwise it's appended
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to the entire CREATE TABLE or CREATE INDEX statement.
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"""
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return ''
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def prep_for_like_query(self, x):
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"""Prepares a value for use in a LIKE query."""
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return force_text(x).replace("\\", "\\\\").replace("%", "\%").replace("_", "\_")
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# Same as prep_for_like_query(), but called for "iexact" matches, which
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# need not necessarily be implemented using "LIKE" in the backend.
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prep_for_iexact_query = prep_for_like_query
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def validate_autopk_value(self, value):
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"""
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Certain backends do not accept some values for "serial" fields
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(for example zero in MySQL). This method will raise a ValueError
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if the value is invalid, otherwise returns validated value.
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"""
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return value
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def adapt_unknown_value(self, value):
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"""
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Transforms a value to something compatible with the backend driver.
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This method only depends on the type of the value. It's designed for
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cases where the target type isn't known, such as .raw() SQL queries.
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As a consequence it may not work perfectly in all circumstances.
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"""
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if isinstance(value, datetime.datetime): # must be before date
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return self.adapt_datetimefield_value(value)
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elif isinstance(value, datetime.date):
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return self.adapt_datefield_value(value)
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elif isinstance(value, datetime.time):
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return self.adapt_timefield_value(value)
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elif isinstance(value, decimal.Decimal):
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return self.adapt_decimalfield_value(value)
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else:
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return value
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def adapt_datefield_value(self, value):
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"""
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Transforms a date value to an object compatible with what is expected
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by the backend driver for date columns.
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"""
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if value is None:
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return None
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return six.text_type(value)
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def adapt_datetimefield_value(self, value):
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"""
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Transforms a datetime value to an object compatible with what is expected
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by the backend driver for datetime columns.
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"""
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if value is None:
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return None
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return six.text_type(value)
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def adapt_timefield_value(self, value):
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"""
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Transforms a time value to an object compatible with what is expected
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by the backend driver for time columns.
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"""
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if value is None:
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return None
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if timezone.is_aware(value):
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raise ValueError("Django does not support timezone-aware times.")
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return six.text_type(value)
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def adapt_decimalfield_value(self, value, max_digits, decimal_places):
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"""
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Transforms a decimal.Decimal value to an object compatible with what is
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expected by the backend driver for decimal (numeric) columns.
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"""
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return utils.format_number(value, max_digits, decimal_places)
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def adapt_ipaddressfield_value(self, value):
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"""
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Transforms a string representation of an IP address into the expected
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type for the backend driver.
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"""
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return value
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def year_lookup_bounds_for_date_field(self, value):
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"""
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Returns a two-elements list with the lower and upper bound to be used
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with a BETWEEN operator to query a DateField value using a year
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lookup.
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`value` is an int, containing the looked-up year.
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"""
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first = datetime.date(value, 1, 1)
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second = datetime.date(value, 12, 31)
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first = self.adapt_datefield_value(first)
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second = self.adapt_datefield_value(second)
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return [first, second]
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def year_lookup_bounds_for_datetime_field(self, value):
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"""
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Returns a two-elements list with the lower and upper bound to be used
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with a BETWEEN operator to query a DateTimeField value using a year
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lookup.
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`value` is an int, containing the looked-up year.
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"""
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first = datetime.datetime(value, 1, 1)
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second = datetime.datetime(value, 12, 31, 23, 59, 59, 999999)
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if settings.USE_TZ:
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tz = timezone.get_current_timezone()
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first = timezone.make_aware(first, tz)
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second = timezone.make_aware(second, tz)
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first = self.adapt_datetimefield_value(first)
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second = self.adapt_datetimefield_value(second)
|
|
return [first, second]
|
|
|
|
def get_db_converters(self, expression):
|
|
"""
|
|
Get a list of functions needed to convert field data.
|
|
|
|
Some field types on some backends do not provide data in the correct
|
|
format, this is the hook for converter functions.
|
|
"""
|
|
return []
|
|
|
|
def convert_durationfield_value(self, value, expression, connection, context):
|
|
if value is not None:
|
|
value = str(decimal.Decimal(value) / decimal.Decimal(1000000))
|
|
value = parse_duration(value)
|
|
return value
|
|
|
|
def check_aggregate_support(self, aggregate_func):
|
|
warnings.warn(
|
|
"check_aggregate_support has been deprecated. Use "
|
|
"check_expression_support instead.",
|
|
RemovedInDjango21Warning, stacklevel=2)
|
|
return self.check_expression_support(aggregate_func)
|
|
|
|
def check_expression_support(self, expression):
|
|
"""
|
|
Check that the backend supports the provided expression.
|
|
|
|
This is used on specific backends to rule out known expressions
|
|
that have problematic or nonexistent implementations. If the
|
|
expression has a known problem, the backend should raise
|
|
NotImplementedError.
|
|
"""
|
|
pass
|
|
|
|
def combine_expression(self, connector, sub_expressions):
|
|
"""Combine a list of subexpressions into a single expression, using
|
|
the provided connecting operator. This is required because operators
|
|
can vary between backends (e.g., Oracle with %% and &) and between
|
|
subexpression types (e.g., date expressions)
|
|
"""
|
|
conn = ' %s ' % connector
|
|
return conn.join(sub_expressions)
|
|
|
|
def combine_duration_expression(self, connector, sub_expressions):
|
|
return self.combine_expression(connector, sub_expressions)
|
|
|
|
def modify_insert_params(self, placeholders, params):
|
|
"""Allow modification of insert parameters. Needed for Oracle Spatial
|
|
backend due to #10888.
|
|
"""
|
|
return params
|
|
|
|
def integer_field_range(self, internal_type):
|
|
"""
|
|
Given an integer field internal type (e.g. 'PositiveIntegerField'),
|
|
returns a tuple of the (min_value, max_value) form representing the
|
|
range of the column type bound to the field.
|
|
"""
|
|
return self.integer_field_ranges[internal_type]
|