# orm/loading.py # Copyright (C) 2005-2014 the SQLAlchemy authors and contributors # # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """private module containing functions used to convert database rows into object instances and associated state. the functions here are called primarily by Query, Mapper, as well as some of the attribute loading strategies. """ from __future__ import absolute_import from .. import util from . import attributes, exc as orm_exc from ..sql import util as sql_util from .util import _none_set, state_str from .. import exc as sa_exc import collections _new_runid = util.counter() def instances(query, cursor, context): """Return an ORM result as an iterator.""" context.runid = _new_runid() filter_fns = [ent.filter_fn for ent in query._entities] filtered = id in filter_fns single_entity = len(query._entities) == 1 and \ query._entities[0].supports_single_entity if filtered: if single_entity: filter_fn = id else: def filter_fn(row): return tuple(fn(x) for x, fn in zip(row, filter_fns)) (process, labels) = \ list(zip(*[ query_entity.row_processor(query, context, cursor) for query_entity in query._entities ])) if not single_entity: keyed_tuple = util.lightweight_named_tuple('result', labels) while True: context.partials = {} if query._yield_per: fetch = cursor.fetchmany(query._yield_per) if not fetch: break else: fetch = cursor.fetchall() if single_entity: proc = process[0] rows = [proc(row) for row in fetch] else: rows = [keyed_tuple([proc(row) for proc in process]) for row in fetch] if filtered: rows = util.unique_list(rows, filter_fn) for row in rows: yield row if not query._yield_per: break @util.dependencies("sqlalchemy.orm.query") def merge_result(querylib, query, iterator, load=True): """Merge a result into this :class:`.Query` object's Session.""" session = query.session if load: # flush current contents if we expect to load data session._autoflush() autoflush = session.autoflush try: session.autoflush = False single_entity = len(query._entities) == 1 if single_entity: if isinstance(query._entities[0], querylib._MapperEntity): result = [session._merge( attributes.instance_state(instance), attributes.instance_dict(instance), load=load, _recursive={}) for instance in iterator] else: result = list(iterator) else: mapped_entities = [i for i, e in enumerate(query._entities) if isinstance(e, querylib._MapperEntity)] result = [] keys = [ent._label_name for ent in query._entities] keyed_tuple = util.lightweight_named_tuple('result', keys) for row in iterator: newrow = list(row) for i in mapped_entities: if newrow[i] is not None: newrow[i] = session._merge( attributes.instance_state(newrow[i]), attributes.instance_dict(newrow[i]), load=load, _recursive={}) result.append(keyed_tuple(newrow)) return iter(result) finally: session.autoflush = autoflush def get_from_identity(session, key, passive): """Look up the given key in the given session's identity map, check the object for expired state if found. """ instance = session.identity_map.get(key) if instance is not None: state = attributes.instance_state(instance) # expired - ensure it still exists if state.expired: if not passive & attributes.SQL_OK: # TODO: no coverage here return attributes.PASSIVE_NO_RESULT elif not passive & attributes.RELATED_OBJECT_OK: # this mode is used within a flush and the instance's # expired state will be checked soon enough, if necessary return instance try: state(state, passive) except orm_exc.ObjectDeletedError: session._remove_newly_deleted([state]) return None return instance else: return None def load_on_ident(query, key, refresh_state=None, lockmode=None, only_load_props=None): """Load the given identity key from the database.""" if key is not None: ident = key[1] else: ident = None if refresh_state is None: q = query._clone() q._get_condition() else: q = query._clone() if ident is not None: mapper = query._mapper_zero() (_get_clause, _get_params) = mapper._get_clause # None present in ident - turn those comparisons # into "IS NULL" if None in ident: nones = set([ _get_params[col].key for col, value in zip(mapper.primary_key, ident) if value is None ]) _get_clause = sql_util.adapt_criterion_to_null( _get_clause, nones) _get_clause = q._adapt_clause(_get_clause, True, False) q._criterion = _get_clause params = dict([ (_get_params[primary_key].key, id_val) for id_val, primary_key in zip(ident, mapper.primary_key) ]) q._params = params if lockmode is not None: version_check = True q = q.with_lockmode(lockmode) elif query._for_update_arg is not None: version_check = True q._for_update_arg = query._for_update_arg else: version_check = False q._get_options( populate_existing=bool(refresh_state), version_check=version_check, only_load_props=only_load_props, refresh_state=refresh_state) q._order_by = None try: return q.one() except orm_exc.NoResultFound: return None def instance_processor(mapper, context, result, path, adapter, polymorphic_from=None, only_load_props=None, refresh_state=None, polymorphic_discriminator=None): """Produce a mapper level row processor callable which processes rows into mapped instances.""" # note that this method, most of which exists in a closure # called _instance(), resists being broken out, as # attempts to do so tend to add significant function # call overhead. _instance() is the most # performance-critical section in the whole ORM. pk_cols = mapper.primary_key if polymorphic_from or refresh_state: polymorphic_switch = None else: polymorphic_switch = _polymorphic_switch( context, mapper, result, path, polymorphic_discriminator, adapter) version_id_col = mapper.version_id_col if adapter: pk_cols = [adapter.columns[c] for c in pk_cols] if version_id_col is not None: version_id_col = adapter.columns[version_id_col] identity_class = mapper._identity_class populators = collections.defaultdict(list) props = mapper._props.values() if only_load_props is not None: props = (p for p in props if p.key in only_load_props) for prop in props: prop.create_row_processor( context, path, mapper, result, adapter, populators) eager_populators = populators.get('eager', ()) load_path = context.query._current_path + path \ if context.query._current_path.path else path session_identity_map = context.session.identity_map populate_existing = context.populate_existing or mapper.always_refresh load_evt = bool(mapper.class_manager.dispatch.load) refresh_evt = bool(mapper.class_manager.dispatch.refresh) instance_state = attributes.instance_state instance_dict = attributes.instance_dict session_id = context.session.hash_key version_check = context.version_check runid = context.runid if refresh_state: refresh_identity_key = refresh_state.key if refresh_identity_key is None: # super-rare condition; a refresh is being called # on a non-instance-key instance; this is meant to only # occur within a flush() refresh_identity_key = \ mapper._identity_key_from_state(refresh_state) else: refresh_identity_key = None if mapper.allow_partial_pks: is_not_primary_key = _none_set.issuperset else: is_not_primary_key = _none_set.intersection def _instance(row): # if we are doing polymorphic, dispatch # to a different _instance() method specific to # the subclass mapper if polymorphic_switch is not None: result = polymorphic_switch(row) if result is not False: return result # determine the state that we'll be populating if refresh_identity_key: # fixed state that we're refreshing state = refresh_state instance = state.obj() dict_ = instance_dict(instance) isnew = state.runid != context.runid currentload = True loaded_instance = False else: # look at the row, see if that identity is in the # session, or we have to create a new one identitykey = ( identity_class, tuple([row[column] for column in pk_cols]) ) instance = session_identity_map.get(identitykey) if instance is not None: # existing instance state = instance_state(instance) dict_ = instance_dict(instance) isnew = state.runid != runid currentload = not isnew loaded_instance = False if version_check and not currentload and \ version_id_col is not None and \ mapper._get_state_attr_by_column( state, dict_, mapper.version_id_col) != \ row[version_id_col]: raise orm_exc.StaleDataError( "Instance '%s' has version id '%s' which " "does not match database-loaded version id '%s'." % (state_str(state), mapper._get_state_attr_by_column( state, dict_, mapper.version_id_col), row[version_id_col])) else: # create a new instance # check for non-NULL values in the primary key columns, # else no entity is returned for the row if is_not_primary_key(identitykey[1]): return None isnew = True currentload = True loaded_instance = True instance = mapper.class_manager.new_instance() dict_ = instance_dict(instance) state = instance_state(instance) state.key = identitykey # attach instance to session. state.session_id = session_id session_identity_map._add_unpresent(state, identitykey) # populate. this looks at whether this state is new # for this load or was existing, and whether or not this # row is the first row with this identity. if currentload or populate_existing: # full population routines. Objects here are either # just created, or we are doing a populate_existing _populate_full( context, load_path, row, state, dict_, isnew, loaded_instance, populate_existing, populators) if isnew: if loaded_instance and load_evt: state.manager.dispatch.load(state, context) elif isnew and refresh_evt: state.manager.dispatch.refresh( state, context, only_load_props) if populate_existing or state.modified: if refresh_state and only_load_props: state._commit(dict_, only_load_props) else: state._commit_all(dict_, session_identity_map) else: # partial population routines, for objects that were already # in the Session, but a row matches them; apply eager loaders # on existing objects, etc. unloaded = state.unloaded isnew = state not in context.partials if not isnew or unloaded or eager_populators: # state is having a partial set of its attributes # refreshed. Populate those attributes, # and add to the "context.partials" collection. to_load = _populate_partial( context, load_path, row, state, dict_, isnew, unloaded, populators) for key, pop in eager_populators: if key not in unloaded: pop(state, dict_, row) if isnew: if refresh_evt: state.manager.dispatch.refresh(state, context, to_load) state._commit(dict_, to_load) return instance return _instance from sqlalchemy.cloader import _populate_full def _dont_populate_full( context, load_path, row, state, dict_, isnew, loaded_instance, populate_existing, populators): if isnew: # first time we are seeing a row with this identity. state.runid = context.runid if context.propagate_options: state.load_options = context.propagate_options if state.load_options: state.load_path = load_path for key, getter in populators["quick"]: dict_[key] = getter(row) if populate_existing: for key, set_callable in populators["expire"]: dict_.pop(key, None) if set_callable: state.callables[key] = state else: for key, set_callable in populators["expire"]: if set_callable: state.callables[key] = state for key, populator in populators["new"]: populator(state, dict_, row) for key, populator in populators["delayed"]: populator(state, dict_, row) else: # have already seen rows with this identity. for key, populator in populators["existing"]: populator(state, dict_, row) def _populate_partial( context, load_path, row, state, dict_, isnew, unloaded, populators): if not isnew: to_load = context.partials[state] for key, populator in populators["existing"]: if key not in to_load: continue populator(state, dict_, row) else: to_load = unloaded context.partials[state] = to_load if context.propagate_options: state.load_options = context.propagate_options if state.load_options: state.load_path = load_path for key, getter in populators["quick"]: if key not in to_load: continue dict_[key] = getter(row) for key, set_callable in populators["expire"]: if key not in to_load: continue dict_.pop(key, None) if set_callable: state.callables[key] = state for key, populator in populators["new"]: if key not in to_load: continue populator(state, dict_, row) for key, populator in populators["delayed"]: if key not in to_load: continue populator(state, dict_, row) return to_load def _polymorphic_switch( context, mapper, result, path, polymorphic_discriminator, adapter): if polymorphic_discriminator is not None: polymorphic_on = polymorphic_discriminator else: polymorphic_on = mapper.polymorphic_on if polymorphic_on is None: return None def configure_subclass_mapper(discriminator): try: sub_mapper = mapper.polymorphic_map[discriminator] except KeyError: raise AssertionError( "No such polymorphic_identity %r is defined" % discriminator) if sub_mapper is mapper: return None return instance_processor( sub_mapper, context, result, path, adapter, polymorphic_from=mapper) polymorphic_instances = util.PopulateDict( configure_subclass_mapper ) if adapter: polymorphic_on = adapter.columns[polymorphic_on] def polymorphic_instance(row): discriminator = row[polymorphic_on] if discriminator is not None: _instance = polymorphic_instances[discriminator] if _instance: return _instance(row) else: return False return polymorphic_instance def load_scalar_attributes(mapper, state, attribute_names): """initiate a column-based attribute refresh operation.""" # assert mapper is _state_mapper(state) session = state.session if not session: raise orm_exc.DetachedInstanceError( "Instance %s is not bound to a Session; " "attribute refresh operation cannot proceed" % (state_str(state))) has_key = bool(state.key) result = False if mapper.inherits and not mapper.concrete: statement = mapper._optimized_get_statement(state, attribute_names) if statement is not None: result = load_on_ident( session.query(mapper).from_statement(statement), None, only_load_props=attribute_names, refresh_state=state ) if result is False: if has_key: identity_key = state.key else: # this codepath is rare - only valid when inside a flush, and the # object is becoming persistent but hasn't yet been assigned # an identity_key. # check here to ensure we have the attrs we need. pk_attrs = [mapper._columntoproperty[col].key for col in mapper.primary_key] if state.expired_attributes.intersection(pk_attrs): raise sa_exc.InvalidRequestError( "Instance %s cannot be refreshed - it's not " " persistent and does not " "contain a full primary key." % state_str(state)) identity_key = mapper._identity_key_from_state(state) if (_none_set.issubset(identity_key) and not mapper.allow_partial_pks) or \ _none_set.issuperset(identity_key): util.warn("Instance %s to be refreshed doesn't " "contain a full primary key - can't be refreshed " "(and shouldn't be expired, either)." % state_str(state)) return result = load_on_ident( session.query(mapper), identity_key, refresh_state=state, only_load_props=attribute_names) # if instance is pending, a refresh operation # may not complete (even if PK attributes are assigned) if has_key and result is None: raise orm_exc.ObjectDeletedError(state)