AliasedInsp
is a class within the sqlalchemy.orm.util
module of the SQLAlchemy project.
AliasedClass
and
identity_key
are a couple of other callables within the sqlalchemy.orm.util
package that also have code examples.
sqlalchemy-utils (project documentation and PyPI package information) is a code library with various helper functions and new data types that make it easier to use SQLAlchemy when building projects that involve more specific storage requirements such as currency. The wide array of data types includes ranged values and aggregated attributes.
sqlalchemy-utils / sqlalchemy_utils / functions / orm.py
# orm.py
from collections import OrderedDict
from functools import partial
from inspect import isclass
from operator import attrgetter
import six
import sqlalchemy as sa
from sqlalchemy.engine.interfaces import Dialect
from sqlalchemy.ext.hybrid import hybrid_property
from sqlalchemy.orm import mapperlib
from sqlalchemy.orm.attributes import InstrumentedAttribute
from sqlalchemy.orm.exc import UnmappedInstanceError
from sqlalchemy.orm.properties import ColumnProperty, RelationshipProperty
from sqlalchemy.orm.query import _ColumnEntity
from sqlalchemy.orm.session import object_session
from sqlalchemy.orm.util import AliasedInsp
from ..utils import is_sequence
def get_class_by_table(base, table, data=None):
found_classes = set(
c for c in base._decl_class_registry.values()
if hasattr(c, '__table__') and c.__table__ is table
)
if len(found_classes) > 1:
if not data:
raise ValueError(
"Multiple declarative classes found for table '{0}'. "
"Please provide data parameter for this function to be able "
"to determine polymorphic scenarios.".format(
table.name
)
)
else:
for cls in found_classes:
mapper = sa.inspect(cls)
polymorphic_on = mapper.polymorphic_on.name
if polymorphic_on in data:
if data[polymorphic_on] == mapper.polymorphic_identity:
## ... source file abbreviated to get to AliasedInsp examples ...
return mapper.get_property_by_column(column).key
except sa.orm.exc.UnmappedColumnError:
for key, c in mapper.columns.items():
if c.name == column.name and c.table is column.table:
return key
raise sa.orm.exc.UnmappedColumnError(
'No column %s is configured on mapper %s...' %
(column, mapper)
)
def get_mapper(mixed):
if isinstance(mixed, sa.orm.query._MapperEntity):
mixed = mixed.expr
elif isinstance(mixed, sa.Column):
mixed = mixed.table
elif isinstance(mixed, sa.orm.query._ColumnEntity):
mixed = mixed.expr
if isinstance(mixed, sa.orm.Mapper):
return mixed
if isinstance(mixed, sa.orm.util.AliasedClass):
return sa.inspect(mixed).mapper
if isinstance(mixed, sa.sql.selectable.Alias):
mixed = mixed.element
if isinstance(mixed, AliasedInsp):
return mixed.mapper
if isinstance(mixed, sa.orm.attributes.InstrumentedAttribute):
mixed = mixed.class_
if isinstance(mixed, sa.Table):
mappers = [
mapper for mapper in mapperlib._mapper_registry
if mixed in mapper.tables
]
if len(mappers) > 1:
raise ValueError(
"Multiple mappers found for table '%s'." % mixed.name
)
elif not mappers:
raise ValueError(
"Could not get mapper for table '%s'." % mixed.name
)
else:
return mappers[0]
if not isclass(mixed):
mixed = type(mixed)
return sa.inspect(mixed)
def get_bind(obj):
## ... source file abbreviated to get to AliasedInsp examples ...
else d['entity']
for d in query.column_descriptions
]
return [
get_query_entity(expr) for expr in exprs
] + [
get_query_entity(entity) for entity in query._join_entities
]
def is_labeled_query(expr):
return (
isinstance(expr, sa.sql.elements.Label) and
isinstance(
list(expr.base_columns)[0],
(sa.sql.selectable.Select, sa.sql.selectable.ScalarSelect)
)
)
def get_query_entity(expr):
if isinstance(expr, sa.orm.attributes.InstrumentedAttribute):
return expr.parent.class_
elif isinstance(expr, sa.Column):
return expr.table
elif isinstance(expr, AliasedInsp):
return expr.entity
return expr
def get_query_entity_by_alias(query, alias):
entities = get_query_entities(query)
if not alias:
return entities[0]
for entity in entities:
if isinstance(entity, sa.orm.util.AliasedClass):
name = sa.inspect(entity).name
else:
name = get_mapper(entity).tables[0].name
if name == alias:
return entity
def get_polymorphic_mappers(mixed):
if isinstance(mixed, AliasedInsp):
return mixed.with_polymorphic_mappers
else:
return mixed.polymorphic_map.values()
def get_query_descriptor(query, entity, attr):
if attr in query_labels(query):
return attr
else:
entity = get_query_entity_by_alias(query, entity)
if entity:
descriptor = get_descriptor(entity, attr)
if (
hasattr(descriptor, 'property') and
isinstance(descriptor.property, sa.orm.RelationshipProperty)
):
return
return descriptor
def get_descriptor(entity, attr):
mapper = sa.inspect(entity)
for key, descriptor in get_all_descriptors(mapper).items():
## ... source file continues with no further AliasedInsp examples...