Fixed #19968 -- Dropped support for PostgreSQL < 8.4.

        super(DatabaseOperations, self).__init__(connection)

    def date_extract_sql(self, lookup_type, field_name):

        # http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT

        # http://www.postgresql.org/docs/current/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

        return '(%s)' % conn.join([sql, 'interval \'%s\'' % mods])

    def date_trunc_sql(self, lookup_type, field_name):

        # http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC

        # http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC

        return "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)

    def datetime_extract_sql(self, lookup_type, field_name, tzname):

            params = [tzname]

        else:

            params = []

        # http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT

        # http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT

        if lookup_type == 'week_day':

            # For consistency across backends, we return Sunday=1, Saturday=7.

            sql = "EXTRACT('dow' FROM %s) + 1" % field_name

            params = [tzname]

        else:

            params = []

        # http://www.postgresql.org/docs/8.0/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC

        # http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC

        sql = "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)

        return sql, params

    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 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', 'VAR_POP'):

            if 80200 <= self.connection.pg_version <= 80204:

                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.

column types, such as geographic polygons or even user-created types such as

`PostgreSQL custom types`_, you can define your own Django ``Field`` subclasses.

.. _PostgreSQL custom types: http://www.postgresql.org/docs/8.2/interactive/sql-createtype.html

.. _PostgreSQL custom types: http://www.postgresql.org/docs/current/interactive/sql-createtype.html

Alternatively, you may have a complex Python object that can somehow be

serialized to fit into a standard database column type. This is another case

GEOGRAPHY=0

POSTGIS_SQL=postgis.sql

# For Ubuntu 8.x and 9.x releases.

if [ -d "/usr/share/postgresql-8.3-postgis" ]

then

    POSTGIS_SQL_PATH=/usr/share/postgresql-8.3-postgis

    POSTGIS_SQL=lwpostgis.sql

fi

# For Ubuntu 10.04

if [ -d "/usr/share/postgresql/8.4/contrib" ]

then

==================  ==============================  ==================  =========================================

Database            Library Requirements            Supported Versions  Notes

==================  ==============================  ==================  =========================================

PostgreSQL          GEOS, PROJ.4, PostGIS           8.2+                Requires PostGIS.

PostgreSQL          GEOS, PROJ.4, PostGIS           8.4+                Requires PostGIS.

MySQL               GEOS                            5.x                 Not OGC-compliant; :ref:`limited functionality <mysql-spatial-limitations>`.

Oracle              GEOS                            10.2, 11            XE not supported; not tested with 9.

SQLite              GEOS, GDAL, PROJ.4, SpatiaLite  3.6.+               Requires SpatiaLite 2.3+, pysqlite2 2.5+

PostgreSQL notes

================

Django supports PostgreSQL 8.2 and higher.

PostgreSQL 8.2 to 8.2.4

-----------------------

The implementation of the population statistics aggregates ``STDDEV_POP`` and

``VAR_POP`` that shipped with PostgreSQL 8.2 to 8.2.4 are `known to be

faulty`_. Users of these releases of PostgreSQL are advised to upgrade to

`Release 8.2.5`_ or later. Django will raise a ``NotImplementedError`` if you

attempt to use the ``StdDev(sample=False)`` or ``Variance(sample=False)``

aggregate with a database backend that falls within the affected release range.

.. _known to be faulty: http://archives.postgresql.org/pgsql-bugs/2007-07/msg00046.php

.. _Release 8.2.5: http://www.postgresql.org/docs/devel/static/release-8-2-5.html

Django supports PostgreSQL 8.4 and higher.

PostgreSQL connection settings

-------------------------------

    handle exceptions raised on serialization failures. This option is

    designed for advanced uses.

.. _postgresql-isolation-levels: http://www.postgresql.org/docs/devel/static/transaction-iso.html

.. _postgresql-isolation-levels: http://www.postgresql.org/docs/current/static/transaction-iso.html

Indexes for ``varchar`` and ``text`` columns

--------------------------------------------

lookups that use the ``LIKE`` operator in their SQL, as is done with the

``contains`` and ``startswith`` lookup types.

.. _PostgreSQL operator class: http://www.postgresql.org/docs/8.4/static/indexes-opclass.html

.. _PostgreSQL operator class: http://www.postgresql.org/docs/current/static/indexes-opclass.html

.. _mysql-notes: