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from django.db.backends.postgresql.schema import DatabaseSchemaEditor
from django.db.models.expressions import Col, Func
class PostGISSchemaEditor(DatabaseSchemaEditor):
geom_index_type = "GIST"
geom_index_ops_nd = "GIST_GEOMETRY_OPS_ND"
rast_index_template = "ST_ConvexHull(%(expressions)s)"
sql_alter_column_to_3d = (
"ALTER COLUMN %(column)s TYPE %(type)s USING ST_Force3D(%(column)s)::%(type)s"
)
sql_alter_column_to_2d = (
"ALTER COLUMN %(column)s TYPE %(type)s USING ST_Force2D(%(column)s)::%(type)s"
)
def geo_quote_name(self, name):
return self.connection.ops.geo_quote_name(name)
def _field_should_be_indexed(self, model, field):
if getattr(field, "spatial_index", False):
return True
return super()._field_should_be_indexed(model, field)
def _create_index_sql(self, model, *, fields=None, **kwargs):
if fields is None or len(fields) != 1 or not hasattr(fields[0], "geodetic"):
return super()._create_index_sql(model, fields=fields, **kwargs)
field = fields[0]
expressions = None
opclasses = None
if field.geom_type == "RASTER":
# For raster fields, wrap index creation SQL statement with ST_ConvexHull.
# Indexes on raster columns are based on the convex hull of the raster.
expressions = Func(Col(None, field), template=self.rast_index_template)
fields = None
elif field.dim > 2 and not field.geography:
# Use "nd" ops which are fast on multidimensional cases
opclasses = [self.geom_index_ops_nd]
name = kwargs.get("name")
if not name:
name = self._create_index_name(model._meta.db_table, [field.column], "_id")
return super()._create_index_sql(
model,
fields=fields,
name=name,
using=" USING %s" % self.geom_index_type,
opclasses=opclasses,
expressions=expressions,
)
def _alter_column_type_sql(
self, table, old_field, new_field, new_type, old_collation, new_collation
):
"""
Special case when dimension changed.
"""
if not hasattr(old_field, "dim") or not hasattr(new_field, "dim"):
return super()._alter_column_type_sql(
table, old_field, new_field, new_type, old_collation, new_collation
)
if old_field.dim == 2 and new_field.dim == 3:
sql_alter = self.sql_alter_column_to_3d
elif old_field.dim == 3 and new_field.dim == 2:
sql_alter = self.sql_alter_column_to_2d
else:
sql_alter = self.sql_alter_column_type
return (
(
sql_alter
% {
"column": self.quote_name(new_field.column),
"type": new_type,
"collation": "",
},
[],
),
[],
)
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