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import re
from django.db.backends import BaseDatabaseOperations
# This DatabaseOperations class lives in here instead of base.py because it's
# used by both the 'postgresql' and 'postgresql_psycopg2' backends.
class DatabaseOperations(BaseDatabaseOperations):
def __init__(self, connection):
super(DatabaseOperations, self).__init__()
self._postgres_version = None
self.connection = connection
def _get_postgres_version(self):
if self._postgres_version is None:
from django.db.backends.postgresql.version import get_version
cursor = self.connection.cursor()
self._postgres_version = get_version(cursor)
return self._postgres_version
postgres_version = property(_get_postgres_version)
def date_extract_sql(self, lookup_type, field_name):
# http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
if lookup_type == 'week_day':
# For consistency across backends, we return Sunday=1, Saturday=7.
return "EXTRACT('dow' FROM %s) + 1" % field_name
else:
return "EXTRACT('%s' FROM %s)" % (lookup_type, field_name)
def date_trunc_sql(self, lookup_type, field_name):
# http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC
return "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)
def deferrable_sql(self):
return " DEFERRABLE INITIALLY DEFERRED"
def lookup_cast(self, lookup_type):
lookup = '%s'
# Cast text lookups to text to allow things like filter(x__contains=4)
if lookup_type in ('iexact', 'contains', 'icontains', 'startswith',
'istartswith', 'endswith', 'iendswith'):
lookup = "%s::text"
# Use UPPER(x) for case-insensitive lookups; it's faster.
if lookup_type in ('iexact', 'icontains', 'istartswith', 'iendswith'):
lookup = 'UPPER(%s)' % lookup
return lookup
def field_cast_sql(self, db_type):
if db_type == 'inet':
return 'HOST(%s)'
return '%s'
def last_insert_id(self, cursor, table_name, pk_name):
# Use pg_get_serial_sequence to get the underlying sequence name
# from the table name and column name (available since PostgreSQL 8)
cursor.execute("SELECT CURRVAL(pg_get_serial_sequence('%s','%s'))" % (
self.quote_name(table_name), pk_name))
return cursor.fetchone()[0]
def no_limit_value(self):
return None
def quote_name(self, name):
if name.startswith('"') and name.endswith('"'):
return name # Quoting once is enough.
return '"%s"' % name
def sql_flush(self, style, tables, sequences):
if tables:
if self.postgres_version[0:2] >= (8,1):
# Postgres 8.1+ can do 'TRUNCATE x, y, z...;'. In fact, it *has to*
# in order to be able to truncate tables referenced by a foreign
# key in any other table. The result is a single SQL TRUNCATE
# statement.
sql = ['%s %s;' % \
(style.SQL_KEYWORD('TRUNCATE'),
style.SQL_FIELD(', '.join([self.quote_name(table) for table in tables]))
)]
else:
# Older versions of Postgres can't do TRUNCATE in a single call, so
# they must use a simple delete.
sql = ['%s %s %s;' % \
(style.SQL_KEYWORD('DELETE'),
style.SQL_KEYWORD('FROM'),
style.SQL_FIELD(self.quote_name(table))
) for table in tables]
# 'ALTER SEQUENCE sequence_name RESTART WITH 1;'... style SQL statements
# to reset sequence indices
for sequence_info in sequences:
table_name = sequence_info['table']
column_name = sequence_info['column']
if not (column_name and len(column_name) > 0):
# This will be the case if it's an m2m using an autogenerated
# intermediate table (see BaseDatabaseIntrospection.sequence_list)
column_name = 'id'
sql.append("%s setval(pg_get_serial_sequence('%s','%s'), 1, false);" % \
(style.SQL_KEYWORD('SELECT'),
style.SQL_TABLE(self.quote_name(table_name)),
style.SQL_FIELD(column_name))
)
return sql
else:
return []
def sequence_reset_sql(self, style, model_list):
from django.db import models
output = []
qn = self.quote_name
for model in model_list:
# Use `coalesce` to set the sequence for each model to the max pk value if there are records,
# or 1 if there are none. Set the `is_called` property (the third argument to `setval`) to true
# if there are records (as the max pk value is already in use), otherwise set it to false.
# Use pg_get_serial_sequence to get the underlying sequence name from the table name
# and column name (available since PostgreSQL 8)
for f in model._meta.local_fields:
if isinstance(f, models.AutoField):
output.append("%s setval(pg_get_serial_sequence('%s','%s'), coalesce(max(%s), 1), max(%s) %s null) %s %s;" % \
(style.SQL_KEYWORD('SELECT'),
style.SQL_TABLE(qn(model._meta.db_table)),
style.SQL_FIELD(f.column),
style.SQL_FIELD(qn(f.column)),
style.SQL_FIELD(qn(f.column)),
style.SQL_KEYWORD('IS NOT'),
style.SQL_KEYWORD('FROM'),
style.SQL_TABLE(qn(model._meta.db_table))))
break # Only one AutoField is allowed per model, so don't bother continuing.
for f in model._meta.many_to_many:
if not f.rel.through:
output.append("%s setval(pg_get_serial_sequence('%s','%s'), coalesce(max(%s), 1), max(%s) %s null) %s %s;" % \
(style.SQL_KEYWORD('SELECT'),
style.SQL_TABLE(qn(f.m2m_db_table())),
style.SQL_FIELD('id'),
style.SQL_FIELD(qn('id')),
style.SQL_FIELD(qn('id')),
style.SQL_KEYWORD('IS NOT'),
style.SQL_KEYWORD('FROM'),
style.SQL_TABLE(qn(f.m2m_db_table()))))
return output
def savepoint_create_sql(self, sid):
return "SAVEPOINT %s" % sid
def savepoint_commit_sql(self, sid):
return "RELEASE SAVEPOINT %s" % sid
def savepoint_rollback_sql(self, sid):
return "ROLLBACK TO SAVEPOINT %s" % sid
def prep_for_iexact_query(self, x):
return x
def check_aggregate_support(self, aggregate):
"""Check that the backend fully supports the provided aggregate.
The population and sample statistics (STDDEV_POP, STDDEV_SAMP,
VAR_POP, VAR_SAMP) were first implemented in Postgres 8.2.
The implementation of population statistics (STDDEV_POP and VAR_POP)
under Postgres 8.2 - 8.2.4 is known to be faulty. Raise
NotImplementedError if this is the database in use.
"""
if aggregate.sql_function in ('STDDEV_POP', 'STDDEV_SAMP', 'VAR_POP', 'VAR_SAMP'):
if self.postgres_version[0:2] < (8,2):
raise NotImplementedError('PostgreSQL does not support %s prior to version 8.2. Please upgrade your version of PostgreSQL.' % aggregate.sql_function)
if aggregate.sql_function in ('STDDEV_POP', 'VAR_POP'):
if self.postgres_version[0:2] == (8,2):
if self.postgres_version[2] is None or self.postgres_version[2] <= 4:
raise NotImplementedError('PostgreSQL 8.2 to 8.2.4 is known to have a faulty implementation of %s. Please upgrade your version of PostgreSQL.' % aggregate.sql_function)
def max_name_length(self):
"""
Returns the maximum length of an identifier.
Note that the maximum length of an identifier is 63 by default, but can
be changed by recompiling PostgreSQL after editing the NAMEDATALEN
macro in src/include/pg_config_manual.h .
This implementation simply returns 63, but can easily be overridden by a
custom database backend that inherits most of its behavior from this one.
"""
return 63
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