669 lines
22 KiB
Python
669 lines
22 KiB
Python
# orm/loading.py
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# Copyright (C) 2005-2015 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""private module containing functions used to convert database
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rows into object instances and associated state.
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the functions here are called primarily by Query, Mapper,
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as well as some of the attribute loading strategies.
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"""
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from __future__ import absolute_import
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from .. import util
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from . import attributes, exc as orm_exc
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from ..sql import util as sql_util
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from . import strategy_options
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from .util import _none_set, state_str
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from .base import _SET_DEFERRED_EXPIRED, _DEFER_FOR_STATE
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from .. import exc as sa_exc
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import collections
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_new_runid = util.counter()
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def instances(query, cursor, context):
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"""Return an ORM result as an iterator."""
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context.runid = _new_runid()
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filter_fns = [ent.filter_fn for ent in query._entities]
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filtered = id in filter_fns
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single_entity = len(query._entities) == 1 and \
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query._entities[0].supports_single_entity
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if filtered:
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if single_entity:
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filter_fn = id
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else:
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def filter_fn(row):
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return tuple(fn(x) for x, fn in zip(row, filter_fns))
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try:
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(process, labels) = \
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list(zip(*[
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query_entity.row_processor(query,
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context, cursor)
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for query_entity in query._entities
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]))
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if not single_entity:
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keyed_tuple = util.lightweight_named_tuple('result', labels)
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while True:
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context.partials = {}
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if query._yield_per:
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fetch = cursor.fetchmany(query._yield_per)
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if not fetch:
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break
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else:
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fetch = cursor.fetchall()
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if single_entity:
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proc = process[0]
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rows = [proc(row) for row in fetch]
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else:
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rows = [keyed_tuple([proc(row) for proc in process])
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for row in fetch]
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if filtered:
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rows = util.unique_list(rows, filter_fn)
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for row in rows:
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yield row
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if not query._yield_per:
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break
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except Exception as err:
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cursor.close()
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util.raise_from_cause(err)
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@util.dependencies("sqlalchemy.orm.query")
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def merge_result(querylib, query, iterator, load=True):
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"""Merge a result into this :class:`.Query` object's Session."""
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session = query.session
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if load:
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# flush current contents if we expect to load data
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session._autoflush()
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autoflush = session.autoflush
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try:
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session.autoflush = False
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single_entity = len(query._entities) == 1
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if single_entity:
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if isinstance(query._entities[0], querylib._MapperEntity):
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result = [session._merge(
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attributes.instance_state(instance),
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attributes.instance_dict(instance),
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load=load, _recursive={})
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for instance in iterator]
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else:
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result = list(iterator)
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else:
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mapped_entities = [i for i, e in enumerate(query._entities)
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if isinstance(e, querylib._MapperEntity)]
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result = []
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keys = [ent._label_name for ent in query._entities]
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keyed_tuple = util.lightweight_named_tuple('result', keys)
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for row in iterator:
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newrow = list(row)
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for i in mapped_entities:
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if newrow[i] is not None:
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newrow[i] = session._merge(
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attributes.instance_state(newrow[i]),
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attributes.instance_dict(newrow[i]),
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load=load, _recursive={})
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result.append(keyed_tuple(newrow))
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return iter(result)
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finally:
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session.autoflush = autoflush
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def get_from_identity(session, key, passive):
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"""Look up the given key in the given session's identity map,
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check the object for expired state if found.
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"""
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instance = session.identity_map.get(key)
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if instance is not None:
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state = attributes.instance_state(instance)
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# expired - ensure it still exists
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if state.expired:
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if not passive & attributes.SQL_OK:
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# TODO: no coverage here
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return attributes.PASSIVE_NO_RESULT
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elif not passive & attributes.RELATED_OBJECT_OK:
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# this mode is used within a flush and the instance's
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# expired state will be checked soon enough, if necessary
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return instance
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try:
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state._load_expired(state, passive)
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except orm_exc.ObjectDeletedError:
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session._remove_newly_deleted([state])
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return None
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return instance
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else:
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return None
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def load_on_ident(query, key,
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refresh_state=None, lockmode=None,
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only_load_props=None):
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"""Load the given identity key from the database."""
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if key is not None:
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ident = key[1]
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else:
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ident = None
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if refresh_state is None:
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q = query._clone()
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q._get_condition()
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else:
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q = query._clone()
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if ident is not None:
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mapper = query._mapper_zero()
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(_get_clause, _get_params) = mapper._get_clause
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# None present in ident - turn those comparisons
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# into "IS NULL"
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if None in ident:
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nones = set([
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_get_params[col].key for col, value in
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zip(mapper.primary_key, ident) if value is None
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])
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_get_clause = sql_util.adapt_criterion_to_null(
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_get_clause, nones)
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_get_clause = q._adapt_clause(_get_clause, True, False)
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q._criterion = _get_clause
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params = dict([
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(_get_params[primary_key].key, id_val)
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for id_val, primary_key in zip(ident, mapper.primary_key)
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])
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q._params = params
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if lockmode is not None:
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version_check = True
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q = q.with_lockmode(lockmode)
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elif query._for_update_arg is not None:
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version_check = True
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q._for_update_arg = query._for_update_arg
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else:
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version_check = False
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q._get_options(
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populate_existing=bool(refresh_state),
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version_check=version_check,
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only_load_props=only_load_props,
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refresh_state=refresh_state)
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q._order_by = None
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try:
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return q.one()
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except orm_exc.NoResultFound:
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return None
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def _setup_entity_query(
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context, mapper, query_entity,
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path, adapter, column_collection,
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with_polymorphic=None, only_load_props=None,
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polymorphic_discriminator=None, **kw):
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if with_polymorphic:
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poly_properties = mapper._iterate_polymorphic_properties(
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with_polymorphic)
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else:
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poly_properties = mapper._polymorphic_properties
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quick_populators = {}
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path.set(
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context.attributes,
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"memoized_setups",
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quick_populators)
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for value in poly_properties:
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if only_load_props and \
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value.key not in only_load_props:
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continue
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value.setup(
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context,
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query_entity,
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path,
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adapter,
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only_load_props=only_load_props,
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column_collection=column_collection,
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memoized_populators=quick_populators,
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**kw
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)
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if polymorphic_discriminator is not None and \
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polymorphic_discriminator \
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is not mapper.polymorphic_on:
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if adapter:
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pd = adapter.columns[polymorphic_discriminator]
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else:
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pd = polymorphic_discriminator
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column_collection.append(pd)
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def _instance_processor(
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mapper, context, result, path, adapter,
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only_load_props=None, refresh_state=None,
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polymorphic_discriminator=None,
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_polymorphic_from=None):
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"""Produce a mapper level row processor callable
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which processes rows into mapped instances."""
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# note that this method, most of which exists in a closure
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# called _instance(), resists being broken out, as
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# attempts to do so tend to add significant function
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# call overhead. _instance() is the most
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# performance-critical section in the whole ORM.
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pk_cols = mapper.primary_key
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if adapter:
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pk_cols = [adapter.columns[c] for c in pk_cols]
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identity_class = mapper._identity_class
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populators = collections.defaultdict(list)
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props = mapper._prop_set
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if only_load_props is not None:
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props = props.intersection(
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mapper._props[k] for k in only_load_props)
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quick_populators = path.get(
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context.attributes, "memoized_setups", _none_set)
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for prop in props:
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if prop in quick_populators:
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# this is an inlined path just for column-based attributes.
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col = quick_populators[prop]
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if col is _DEFER_FOR_STATE:
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populators["new"].append(
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(prop.key, prop._deferred_column_loader))
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elif col is _SET_DEFERRED_EXPIRED:
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# note that in this path, we are no longer
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# searching in the result to see if the column might
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# be present in some unexpected way.
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populators["expire"].append((prop.key, False))
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else:
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if adapter:
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col = adapter.columns[col]
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getter = result._getter(col)
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if getter:
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populators["quick"].append((prop.key, getter))
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else:
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# fall back to the ColumnProperty itself, which
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# will iterate through all of its columns
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# to see if one fits
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prop.create_row_processor(
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context, path, mapper, result, adapter, populators)
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else:
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prop.create_row_processor(
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context, path, mapper, result, adapter, populators)
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propagate_options = context.propagate_options
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if propagate_options:
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load_path = context.query._current_path + path \
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if context.query._current_path.path else path
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session_identity_map = context.session.identity_map
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populate_existing = context.populate_existing or mapper.always_refresh
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load_evt = bool(mapper.class_manager.dispatch.load)
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refresh_evt = bool(mapper.class_manager.dispatch.refresh)
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instance_state = attributes.instance_state
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instance_dict = attributes.instance_dict
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session_id = context.session.hash_key
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version_check = context.version_check
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runid = context.runid
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if refresh_state:
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refresh_identity_key = refresh_state.key
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if refresh_identity_key is None:
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# super-rare condition; a refresh is being called
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# on a non-instance-key instance; this is meant to only
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# occur within a flush()
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refresh_identity_key = \
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mapper._identity_key_from_state(refresh_state)
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else:
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refresh_identity_key = None
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if mapper.allow_partial_pks:
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is_not_primary_key = _none_set.issuperset
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else:
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is_not_primary_key = _none_set.intersection
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def _instance(row):
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# determine the state that we'll be populating
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if refresh_identity_key:
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# fixed state that we're refreshing
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state = refresh_state
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instance = state.obj()
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dict_ = instance_dict(instance)
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isnew = state.runid != runid
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currentload = True
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loaded_instance = False
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else:
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# look at the row, see if that identity is in the
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# session, or we have to create a new one
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identitykey = (
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identity_class,
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tuple([row[column] for column in pk_cols])
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)
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instance = session_identity_map.get(identitykey)
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if instance is not None:
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# existing instance
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state = instance_state(instance)
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dict_ = instance_dict(instance)
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isnew = state.runid != runid
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currentload = not isnew
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loaded_instance = False
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if version_check and not currentload:
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_validate_version_id(mapper, state, dict_, row, adapter)
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else:
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# create a new instance
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# check for non-NULL values in the primary key columns,
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# else no entity is returned for the row
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if is_not_primary_key(identitykey[1]):
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return None
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isnew = True
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currentload = True
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loaded_instance = True
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instance = mapper.class_manager.new_instance()
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dict_ = instance_dict(instance)
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state = instance_state(instance)
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state.key = identitykey
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# attach instance to session.
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state.session_id = session_id
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session_identity_map._add_unpresent(state, identitykey)
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# populate. this looks at whether this state is new
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# for this load or was existing, and whether or not this
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# row is the first row with this identity.
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if currentload or populate_existing:
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# full population routines. Objects here are either
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# just created, or we are doing a populate_existing
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if isnew and propagate_options:
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state.load_options = propagate_options
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state.load_path = load_path
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_populate_full(
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context, row, state, dict_, isnew,
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loaded_instance, populate_existing, populators)
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if isnew:
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if loaded_instance and load_evt:
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state.manager.dispatch.load(state, context)
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elif refresh_evt:
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state.manager.dispatch.refresh(
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state, context, only_load_props)
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if populate_existing or state.modified:
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if refresh_state and only_load_props:
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state._commit(dict_, only_load_props)
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else:
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state._commit_all(dict_, session_identity_map)
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else:
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# partial population routines, for objects that were already
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# in the Session, but a row matches them; apply eager loaders
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# on existing objects, etc.
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unloaded = state.unloaded
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isnew = state not in context.partials
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if not isnew or unloaded or populators["eager"]:
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# state is having a partial set of its attributes
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# refreshed. Populate those attributes,
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# and add to the "context.partials" collection.
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to_load = _populate_partial(
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context, row, state, dict_, isnew,
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unloaded, populators)
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if isnew:
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if refresh_evt:
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state.manager.dispatch.refresh(
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state, context, to_load)
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state._commit(dict_, to_load)
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return instance
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if mapper.polymorphic_map and not _polymorphic_from and not refresh_state:
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# if we are doing polymorphic, dispatch to a different _instance()
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# method specific to the subclass mapper
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_instance = _decorate_polymorphic_switch(
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_instance, context, mapper, result, path,
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polymorphic_discriminator, adapter)
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return _instance
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def _populate_full(
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context, row, state, dict_, isnew,
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loaded_instance, populate_existing, populators):
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if isnew:
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# first time we are seeing a row with this identity.
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state.runid = context.runid
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for key, getter in populators["quick"]:
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dict_[key] = getter(row)
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if populate_existing:
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for key, set_callable in populators["expire"]:
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dict_.pop(key, None)
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if set_callable:
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state.expired_attributes.add(key)
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else:
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for key, set_callable in populators["expire"]:
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if set_callable:
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state.expired_attributes.add(key)
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for key, populator in populators["new"]:
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populator(state, dict_, row)
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for key, populator in populators["delayed"]:
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populator(state, dict_, row)
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else:
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# have already seen rows with this identity.
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for key, populator in populators["existing"]:
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populator(state, dict_, row)
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|
|
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def _populate_partial(
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context, row, state, dict_, isnew,
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unloaded, populators):
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if not isnew:
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to_load = context.partials[state]
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for key, populator in populators["existing"]:
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if key in to_load:
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populator(state, dict_, row)
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else:
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to_load = unloaded
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context.partials[state] = to_load
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for key, getter in populators["quick"]:
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if key in to_load:
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dict_[key] = getter(row)
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for key, set_callable in populators["expire"]:
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if key in to_load:
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dict_.pop(key, None)
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if set_callable:
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state.expired_attributes.add(key)
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for key, populator in populators["new"]:
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if key in to_load:
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populator(state, dict_, row)
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for key, populator in populators["delayed"]:
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if key in to_load:
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populator(state, dict_, row)
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for key, populator in populators["eager"]:
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if key not in unloaded:
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populator(state, dict_, row)
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return to_load
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|
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def _validate_version_id(mapper, state, dict_, row, adapter):
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version_id_col = mapper.version_id_col
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if version_id_col is None:
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return
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if adapter:
|
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version_id_col = adapter.columns[version_id_col]
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|
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if mapper._get_state_attr_by_column(
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state, dict_, mapper.version_id_col) != row[version_id_col]:
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raise orm_exc.StaleDataError(
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"Instance '%s' has version id '%s' which "
|
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"does not match database-loaded version id '%s'."
|
|
% (state_str(state), mapper._get_state_attr_by_column(
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|
state, dict_, mapper.version_id_col),
|
|
row[version_id_col]))
|
|
|
|
|
|
def _decorate_polymorphic_switch(
|
|
instance_fn, 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 instance_fn
|
|
|
|
if adapter:
|
|
polymorphic_on = adapter.columns[polymorphic_on]
|
|
|
|
def configure_subclass_mapper(discriminator):
|
|
try:
|
|
sub_mapper = mapper.polymorphic_map[discriminator]
|
|
except KeyError:
|
|
raise AssertionError(
|
|
"No such polymorphic_identity %r is defined" %
|
|
discriminator)
|
|
else:
|
|
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
|
|
)
|
|
|
|
def polymorphic_instance(row):
|
|
discriminator = row[polymorphic_on]
|
|
if discriminator is not None:
|
|
_instance = polymorphic_instances[discriminator]
|
|
if _instance:
|
|
return _instance(row)
|
|
return instance_fn(row)
|
|
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:
|
|
# because we are using Core to produce a select() that we
|
|
# pass to the Query, we aren't calling setup() for mapped
|
|
# attributes; in 1.0 this means deferred attrs won't get loaded
|
|
# by default
|
|
statement = mapper._optimized_get_statement(state, attribute_names)
|
|
if statement is not None:
|
|
result = load_on_ident(
|
|
session.query(mapper).
|
|
options(
|
|
strategy_options.Load(mapper).undefer("*")
|
|
).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_limited(
|
|
"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)
|