I expected to be able to map both sides of the relationship from a
resultset with the proper columns. However it appears to still lazy
load all the child objects. Short example (works against trunk):
import pkg_resources
pkg_resources.require( "sqlalchemy" )
pkg_resources.require( "pysqlite" )
from sqlalchemy import *
# Setup classes, tables, mappers
metadata = BoundMetaData( 'sqlite:////tmp/test.db' )
metadata.engine.echo = True
class A( object ):
pass
class B( object ):
pass
A.table = Table( "table_a", metadata,
Column( "id", Integer, primary_key=True),
Column( "name", String(20) ) )
B.table = Table( "table_b", metadata,
Column( "id", Integer, primary_key=True),
Column( "name", String(20) ),
Column( "table_a_id", Integer, ForeignKey( "table_a.id" ) ) )
mapper( B, B.table )
mapper( A, A.table, properties=dict( bs=relation( B, backref="a" ) ) )
metadata.create_all()
# Insert some stuff
session = create_session()
for i in range( 10 ):
a = A()
a.name = "A_%d" % i
session.save( a )
for j in range( 10 ):
b = B()
b.name= "B_%d" % i
b.a = a
session.save( b )
session.flush()
session.clear()
# Map from select
results = select( [ A.table, B.table ], A.c.id == B.c.table_a_id,
use_labels=True ).execute()
some_as = class_mapper( A ).instances( results, session, with_options=
[eagerload('bs')] )
# At this point many queries against 'b_table'
for a in some_as:
list( a.bs )
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