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- import six
- from sqlalchemy import inspect
- from sqlalchemy.orm import defer
- from sqlalchemy.orm.properties import ColumnProperty
- from sqlalchemy.orm.query import _ColumnEntity
- from sqlalchemy.orm.mapper import Mapper
- def property_names(properties):
- names = []
- for property_ in properties:
- if isinstance(property_, six.string_types):
- names.append(property_)
- else:
- names.append(
- '%s.%s' % (
- property_.class_.__name__,
- property_.key
- )
- )
- return names
- def query_entities(query):
- entities = []
- for entity in query._entities:
- if not isinstance(entity, _ColumnEntity):
- entities.append(entity.entity_zero.class_)
- for entity in query._join_entities:
- if isinstance(entity, Mapper):
- entities.append(entity.class_)
- else:
- entities.append(entity)
- return entities
- def defer_except(query, columns):
- """
- Deferred loads all columns in given query, except the ones given.
- This function is very useful when working with models with myriad of
- columns and you want to deferred load many columns.
- >>> from sqlalchemy_utils import defer_except
- >>> query = session.query(Article)
- >>> query = defer_except(Article, [Article.id, Article.name])
- :param columns: columns not to deferred load
- """
- model = query._entities[0].entity_zero.class_
- for property_ in inspect(model).attrs:
- if isinstance(property_, ColumnProperty):
- column = property_.columns[0]
- if column.name not in columns:
- query = query.options(defer(property_.key))
- return query
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