Source code for sqlalchemy_utils.functions.orm

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

try:
    from sqlalchemy.orm.context import _ColumnEntity, _MapperEntity
except ImportError:  # SQLAlchemy <1.4
    from sqlalchemy.orm.query import _ColumnEntity, _MapperEntity

from sqlalchemy.orm.session import object_session
from sqlalchemy.orm.util import AliasedInsp

from ..utils import is_sequence


[docs]def get_class_by_table(base, table, data=None): """ Return declarative class associated with given table. If no class is found this function returns `None`. If multiple classes were found (polymorphic cases) additional `data` parameter can be given to hint which class to return. :: class User(Base): __tablename__ = 'entity' id = sa.Column(sa.Integer, primary_key=True) name = sa.Column(sa.String) get_class_by_table(Base, User.__table__) # User class This function also supports models using single table inheritance. Additional data paratemer should be provided in these case. :: class Entity(Base): __tablename__ = 'entity' id = sa.Column(sa.Integer, primary_key=True) name = sa.Column(sa.String) type = sa.Column(sa.String) __mapper_args__ = { 'polymorphic_on': type, 'polymorphic_identity': 'entity' } class User(Entity): __mapper_args__ = { 'polymorphic_identity': 'user' } # Entity class get_class_by_table(Base, Entity.__table__, {'type': 'entity'}) # User class get_class_by_table(Base, Entity.__table__, {'type': 'user'}) :param base: Declarative model base :param table: SQLAlchemy Table object :param data: Data row to determine the class in polymorphic scenarios :return: Declarative class or None. """ found_classes = set( c for c in _get_class_registry(base).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: return cls raise ValueError( "Multiple declarative classes found for table '{0}'. Given " "data row does not match any polymorphic identity of the " "found classes.".format( table.name ) ) elif found_classes: return found_classes.pop() return None
[docs]def get_type(expr): """ Return the associated type with given Column, InstrumentedAttribute, ColumnProperty, RelationshipProperty or other similar SQLAlchemy construct. For constructs wrapping columns this is the column type. For relationships this function returns the relationship mapper class. :param expr: SQLAlchemy Column, InstrumentedAttribute, ColumnProperty or other similar SA construct. :: class User(Base): __tablename__ = 'user' id = sa.Column(sa.Integer, primary_key=True) name = sa.Column(sa.String) class Article(Base): __tablename__ = 'article' id = sa.Column(sa.Integer, primary_key=True) author_id = sa.Column(sa.Integer, sa.ForeignKey(User.id)) author = sa.orm.relationship(User) get_type(User.__table__.c.name) # sa.String() get_type(User.name) # sa.String() get_type(User.name.property) # sa.String() get_type(Article.author) # User .. versionadded: 0.30.9 """ if hasattr(expr, 'type'): return expr.type elif isinstance(expr, InstrumentedAttribute): expr = expr.property if isinstance(expr, ColumnProperty): return expr.columns[0].type elif isinstance(expr, RelationshipProperty): return expr.mapper.class_ raise TypeError("Couldn't inspect type.")
[docs]def cast_if(expression, type_): """ Produce a CAST expression but only if given expression is not of given type already. Assume we have a model with two fields id (Integer) and name (String). :: import sqlalchemy as sa from sqlalchemy_utils import cast_if cast_if(User.id, sa.Integer) # "user".id cast_if(User.name, sa.String) # "user".name cast_if(User.id, sa.String) # CAST("user".id AS TEXT) This function supports scalar values as well. :: cast_if(1, sa.Integer) # 1 cast_if('text', sa.String) # 'text' cast_if(1, sa.String) # CAST(1 AS TEXT) :param expression: A SQL expression, such as a ColumnElement expression or a Python string which will be coerced into a bound literal value. :param type_: A TypeEngine class or instance indicating the type to which the CAST should apply. .. versionadded: 0.30.14 """ try: expr_type = get_type(expression) except TypeError: expr_type = expression check_type = type_().python_type else: check_type = type_ return ( sa.cast(expression, type_) if not isinstance(expr_type, check_type) else expression )
[docs]def get_column_key(model, column): """ Return the key for given column in given model. :param model: SQLAlchemy declarative model object :: class User(Base): __tablename__ = 'user' id = sa.Column(sa.Integer, primary_key=True) name = sa.Column('_name', sa.String) get_column_key(User, User.__table__.c._name) # 'name' .. versionadded: 0.26.5 .. versionchanged: 0.27.11 Throws UnmappedColumnError instead of ValueError when no property was found for given column. This is consistent with how SQLAlchemy works. """ mapper = sa.inspect(model) try: 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) )
[docs]def get_mapper(mixed): """ Return related SQLAlchemy Mapper for given SQLAlchemy object. :param mixed: SQLAlchemy Table / Alias / Mapper / declarative model object :: from sqlalchemy_utils import get_mapper get_mapper(User) get_mapper(User()) get_mapper(User.__table__) get_mapper(User.__mapper__) get_mapper(sa.orm.aliased(User)) get_mapper(sa.orm.aliased(User.__table__)) Raises: ValueError: if multiple mappers were found for given argument .. versionadded: 0.26.1 """ if isinstance(mixed, _MapperEntity): mixed = mixed.expr elif isinstance(mixed, sa.Column): mixed = mixed.table elif isinstance(mixed, _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): if hasattr(mapperlib, '_all_registries'): all_mappers = set() for mapper_registry in mapperlib._all_registries(): all_mappers.update(mapper_registry.mappers) else: # SQLAlchemy <1.4 all_mappers = mapperlib._mapper_registry mappers = [ mapper for mapper in all_mappers 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)
[docs]def get_bind(obj): """ Return the bind for given SQLAlchemy Engine / Connection / declarative model object. :param obj: SQLAlchemy Engine / Connection / declarative model object :: from sqlalchemy_utils import get_bind get_bind(session) # Connection object get_bind(user) """ if hasattr(obj, 'bind'): conn = obj.bind else: try: conn = object_session(obj).bind except UnmappedInstanceError: conn = obj if not hasattr(conn, 'execute'): raise TypeError( 'This method accepts only Session, Engine, Connection and ' 'declarative model objects.' ) return conn
[docs]def get_primary_keys(mixed): """ Return an OrderedDict of all primary keys for given Table object, declarative class or declarative class instance. :param mixed: SA Table object, SA declarative class or SA declarative class instance :: get_primary_keys(User) get_primary_keys(User()) get_primary_keys(User.__table__) get_primary_keys(User.__mapper__) get_primary_keys(sa.orm.aliased(User)) get_primary_keys(sa.orm.aliased(User.__table__)) .. versionchanged: 0.25.3 Made the function return an ordered dictionary instead of generator. This change was made to support primary key aliases. Renamed this function to 'get_primary_keys', formerly 'primary_keys' .. seealso:: :func:`get_columns` """ return OrderedDict( ( (key, column) for key, column in get_columns(mixed).items() if column.primary_key ) )
[docs]def get_tables(mixed): """ Return a set of tables associated with given SQLAlchemy object. Let's say we have three classes which use joined table inheritance TextItem, Article and BlogPost. Article and BlogPost inherit TextItem. :: get_tables(Article) # set([Table('article', ...), Table('text_item')]) get_tables(Article()) get_tables(Article.__mapper__) If the TextItem entity is using with_polymorphic='*' then this function returns all child tables (article and blog_post) as well. :: get_tables(TextItem) # set([Table('text_item', ...)], ...]) .. versionadded: 0.26.0 :param mixed: SQLAlchemy Mapper, Declarative class, Column, InstrumentedAttribute or a SA Alias object wrapping any of these objects. """ if isinstance(mixed, sa.Table): return [mixed] elif isinstance(mixed, sa.Column): return [mixed.table] elif isinstance(mixed, sa.orm.attributes.InstrumentedAttribute): return mixed.parent.tables elif isinstance(mixed, _ColumnEntity): mixed = mixed.expr mapper = get_mapper(mixed) polymorphic_mappers = get_polymorphic_mappers(mapper) if polymorphic_mappers: tables = sum((m.tables for m in polymorphic_mappers), []) else: tables = mapper.tables return tables
[docs]def get_columns(mixed): """ Return a collection of all Column objects for given SQLAlchemy object. The type of the collection depends on the type of the object to return the columns from. :: get_columns(User) get_columns(User()) get_columns(User.__table__) get_columns(User.__mapper__) get_columns(sa.orm.aliased(User)) get_columns(sa.orm.alised(User.__table__)) :param mixed: SA Table object, SA Mapper, SA declarative class, SA declarative class instance or an alias of any of these objects """ if isinstance(mixed, sa.sql.selectable.Selectable): try: return mixed.selected_columns except AttributeError: # SQLAlchemy <1.4 return mixed.c if isinstance(mixed, sa.orm.util.AliasedClass): return sa.inspect(mixed).mapper.columns if isinstance(mixed, sa.orm.Mapper): return mixed.columns if isinstance(mixed, InstrumentedAttribute): return mixed.property.columns if isinstance(mixed, ColumnProperty): return mixed.columns if isinstance(mixed, sa.Column): return [mixed] if not isclass(mixed): mixed = mixed.__class__ return sa.inspect(mixed).columns
def table_name(obj): """ Return table name of given target, declarative class or the table name where the declarative attribute is bound to. """ class_ = getattr(obj, 'class_', obj) try: return class_.__tablename__ except AttributeError: pass try: return class_.__table__.name except AttributeError: pass def getattrs(obj, attrs): return map(partial(getattr, obj), attrs)
[docs]def quote(mixed, ident): """ Conditionally quote an identifier. :: from sqlalchemy_utils import quote engine = create_engine('sqlite:///:memory:') quote(engine, 'order') # '"order"' quote(engine, 'some_other_identifier') # 'some_other_identifier' :param mixed: SQLAlchemy Session / Connection / Engine / Dialect object. :param ident: identifier to conditionally quote """ if isinstance(mixed, Dialect): dialect = mixed else: dialect = get_bind(mixed).dialect return dialect.preparer(dialect).quote(ident)
def _get_query_compile_state(query): if hasattr(query, '_compile_state'): return query._compile_state() else: # SQLAlchemy <1.4 return query def get_polymorphic_mappers(mixed): if isinstance(mixed, AliasedInsp): return mixed.with_polymorphic_mappers else: return mixed.polymorphic_map.values() def get_descriptor(entity, attr): mapper = sa.inspect(entity) for key, descriptor in get_all_descriptors(mapper).items(): if attr == key: prop = ( descriptor.property if hasattr(descriptor, 'property') else None ) if isinstance(prop, ColumnProperty): if isinstance(entity, sa.orm.util.AliasedClass): for c in mapper.selectable.c: if c.key == attr: return c else: # If the property belongs to a class that uses # polymorphic inheritance we have to take into account # situations where the attribute exists in child class # but not in parent class. return getattr(prop.parent.class_, attr) else: # Handle synonyms, relationship properties and hybrid # properties if isinstance(entity, sa.orm.util.AliasedClass): return getattr(entity, attr) try: return getattr(mapper.class_, attr) except AttributeError: pass def get_all_descriptors(expr): if isinstance(expr, sa.sql.selectable.Selectable): return expr.c insp = sa.inspect(expr) try: polymorphic_mappers = get_polymorphic_mappers(insp) except sa.exc.NoInspectionAvailable: return get_mapper(expr).all_orm_descriptors else: attrs = dict(get_mapper(expr).all_orm_descriptors) for submapper in polymorphic_mappers: for key, descriptor in submapper.all_orm_descriptors.items(): if key not in attrs: attrs[key] = descriptor return attrs
[docs]def get_hybrid_properties(model): """ Returns a dictionary of hybrid property keys and hybrid properties for given SQLAlchemy declarative model / mapper. Consider the following model :: from sqlalchemy.ext.hybrid import hybrid_property class Category(Base): __tablename__ = 'category' id = sa.Column(sa.Integer, primary_key=True) name = sa.Column(sa.Unicode(255)) @hybrid_property def lowercase_name(self): return self.name.lower() @lowercase_name.expression def lowercase_name(cls): return sa.func.lower(cls.name) You can now easily get a list of all hybrid property names :: from sqlalchemy_utils import get_hybrid_properties get_hybrid_properties(Category).keys() # ['lowercase_name'] This function also supports aliased classes :: get_hybrid_properties( sa.orm.aliased(Category) ).keys() # ['lowercase_name'] .. versionchanged: 0.26.7 This function now returns a dictionary instead of generator .. versionchanged: 0.30.15 Added support for aliased classes :param model: SQLAlchemy declarative model or mapper """ return dict( (key, prop) for key, prop in get_mapper(model).all_orm_descriptors.items() if isinstance(prop, hybrid_property) )
[docs]def get_declarative_base(model): """ Returns the declarative base for given model class. :param model: SQLAlchemy declarative model """ for parent in model.__bases__: try: parent.metadata return get_declarative_base(parent) except AttributeError: pass return model
def getdotattr(obj_or_class, dot_path, condition=None): """ Allow dot-notated strings to be passed to `getattr`. :: getdotattr(SubSection, 'section.document') getdotattr(subsection, 'section.document') :param obj_or_class: Any object or class :param dot_path: Attribute path with dot mark as separator """ last = obj_or_class for path in str(dot_path).split('.'): getter = attrgetter(path) if is_sequence(last): tmp = [] for element in last: value = getter(element) if is_sequence(value): tmp.extend(value) else: tmp.append(value) last = tmp elif isinstance(last, InstrumentedAttribute): last = getter(last.property.mapper.class_) elif last is None: return None else: last = getter(last) if condition is not None: if is_sequence(last): last = [v for v in last if condition(v)] else: if not condition(last): return None return last def is_deleted(obj): return obj in sa.orm.object_session(obj).deleted
[docs]def has_changes(obj, attrs=None, exclude=None): """ Simple shortcut function for checking if given attributes of given declarative model object have changed during the session. Without parameters this checks if given object has any modificiations. Additionally exclude parameter can be given to check if given object has any changes in any attributes other than the ones given in exclude. :: from sqlalchemy_utils import has_changes user = User() has_changes(user, 'name') # False user.name = u'someone' has_changes(user, 'name') # True has_changes(user) # True You can check multiple attributes as well. :: has_changes(user, ['age']) # True has_changes(user, ['name', 'age']) # True This function also supports excluding certain attributes. :: has_changes(user, exclude=['name']) # False has_changes(user, exclude=['age']) # True .. versionchanged: 0.26.6 Added support for multiple attributes and exclude parameter. :param obj: SQLAlchemy declarative model object :param attrs: Names of the attributes :param exclude: Names of the attributes to exclude """ if attrs: if isinstance(attrs, six.string_types): return ( sa.inspect(obj) .attrs .get(attrs) .history .has_changes() ) else: return any(has_changes(obj, attr) for attr in attrs) else: if exclude is None: exclude = [] return any( attr.history.has_changes() for key, attr in sa.inspect(obj).attrs.items() if key not in exclude )
[docs]def is_loaded(obj, prop): """ Return whether or not given property of given object has been loaded. :: class Article(Base): __tablename__ = 'article' id = sa.Column(sa.Integer, primary_key=True) name = sa.Column(sa.String) content = sa.orm.deferred(sa.Column(sa.String)) article = session.query(Article).get(5) # name gets loaded since its not a deferred property assert is_loaded(article, 'name') # content has not yet been loaded since its a deferred property assert not is_loaded(article, 'content') .. versionadded: 0.27.8 :param obj: SQLAlchemy declarative model object :param prop: Name of the property or InstrumentedAttribute """ return not isinstance( getattr(sa.inspect(obj).attrs, prop).loaded_value, sa.util.langhelpers._symbol )
[docs]def identity(obj_or_class): """ Return the identity of given sqlalchemy declarative model class or instance as a tuple. This differs from obj._sa_instance_state.identity in a way that it always returns the identity even if object is still in transient state ( new object that is not yet persisted into database). Also for classes it returns the identity attributes. :: from sqlalchemy import inspect from sqlalchemy_utils import identity user = User(name=u'John Matrix') session.add(user) identity(user) # None inspect(user).identity # None session.flush() # User now has id but is still in transient state identity(user) # (1,) inspect(user).identity # None session.commit() identity(user) # (1,) inspect(user).identity # (1, ) You can also use identity for classes:: identity(User) # (User.id, ) .. versionadded: 0.21.0 :param obj: SQLAlchemy declarative model object """ return tuple( getattr(obj_or_class, column_key) for column_key in get_primary_keys(obj_or_class).keys() )
[docs]def naturally_equivalent(obj, obj2): """ Returns whether or not two given SQLAlchemy declarative instances are naturally equivalent (all their non primary key properties are equivalent). :: from sqlalchemy_utils import naturally_equivalent user = User(name=u'someone') user2 = User(name=u'someone') user == user2 # False naturally_equivalent(user, user2) # True :param obj: SQLAlchemy declarative model object :param obj2: SQLAlchemy declarative model object to compare with `obj` """ for column_key, column in sa.inspect(obj.__class__).columns.items(): if column.primary_key: continue if not (getattr(obj, column_key) == getattr(obj2, column_key)): return False return True
def _get_class_registry(class_): try: return class_.registry._class_registry except AttributeError: # SQLAlchemy <1.4 return class_._decl_class_registry