Commit 8196e4bd authored by Josh Smeaton's avatar Josh Smeaton
Browse files

Fixed #24154 -- Backends can now check support for expressions

parent 511be357

django/contrib/gis/db/backends/base/operations.py

+4 −4
Original line number Diff line number Diff line
@@ -98,12 +98,12 @@ class BaseSpatialOperations(object): 
        """

        raise NotImplementedError('subclasses of BaseSpatialOperations must provide a geo_db_placeholder() method')



    def check_aggregate_support(self, aggregate):

        if isinstance(aggregate, self.disallowed_aggregates):

    def check_expression_support(self, expression):

        if isinstance(expression, self.disallowed_aggregates):

            raise NotImplementedError(

                "%s spatial aggregation is not supported by this database backend." % aggregate.name

                "%s spatial aggregation is not supported by this database backend." % expression.name

            )

        super(BaseSpatialOperations, self).check_aggregate_support(aggregate)

        super(BaseSpatialOperations, self).check_expression_support(expression)



    def spatial_aggregate_name(self, agg_name):

        raise NotImplementedError('Aggregate support not implemented for this spatial backend.')

django/contrib/gis/db/models/aggregates.py

+3 −0
Original line number Diff line number Diff line
@@ -9,6 +9,9 @@ class GeoAggregate(Aggregate): 
    is_extent = False



    def as_sql(self, compiler, connection):

        # this will be called again in parent, but it's needed now - before

        # we get the spatial_aggregate_name

        connection.ops.check_expression_support(self)

        self.function = connection.ops.spatial_aggregate_name(self.name)

        return super(GeoAggregate, self).as_sql(compiler, connection)

django/db/backends/base/features.py

+3 −5
Original line number Diff line number Diff line 
from django.db.models.aggregates import StdDev

from django.db.models.expressions import Value

from django.db.utils import ProgrammingError

from django.utils.functional import cached_property
@@ -226,12 +228,8 @@ class BaseDatabaseFeatures(object): 
    @cached_property

    def supports_stddev(self):

        """Confirm support for STDDEV and related stats functions."""

        class StdDevPop(object):

            contains_aggregate = True

            sql_function = 'STDDEV_POP'



        try:

            self.connection.ops.check_aggregate_support(StdDevPop())

            self.connection.ops.check_expression_support(StdDev(Value(1)))

            return True

        except NotImplementedError:

            return False

django/db/backends/base/operations.py

+15 −5
Original line number Diff line number Diff line 
import datetime

import decimal

from importlib import import_module

import warnings



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 RemovedInDjango21Warning

from django.utils.encoding import force_text
@@ -517,12 +519,20 @@ class BaseDatabaseOperations(object): 
        return value



    def check_aggregate_support(self, aggregate_func):

        """Check that the backend supports the provided aggregate

        warnings.warn(

            "check_aggregate_support has been deprecated. Use "

            "check_expression_support instead.",

            RemovedInDjango21Warning, stacklevel=2)

        return self.check_expression_support(aggregate_func)



        This is used on specific backends to rule out known aggregates

        that are known to have faulty implementations. If the named

        aggregate function has a known problem, the backend should

        raise NotImplementedError.

    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

django/db/backends/sqlite3/features.py

+1 −1
Original line number Diff line number Diff line
@@ -60,7 +60,7 @@ class DatabaseFeatures(BaseDatabaseFeatures): 
        """Confirm support for STDDEV and related stats functions



        SQLite supports STDDEV as an extension package; so

        connection.ops.check_aggregate_support() can't unilaterally

        connection.ops.check_expression_support() can't unilaterally

        rule out support for STDDEV. We need to manually check

        whether the call works.

        """