def polymorphic_union(table_map, typecolname, aliasname="p_union", cast_nulls=True):
"""Create a ``UNION`` statement used by a polymorphic mapper.
See :ref:`concrete_inheritance` for an example of how
this is used.
:param table_map: mapping of polymorphic identities to
:class:`.Table` objects.
:param typecolname: string name of a "discriminator" column, which will be
derived from the query, producing the polymorphic identity for each row. If
``None``, no polymorphic discriminator is generated.
:param aliasname: name of the :func:`~sqlalchemy.sql.expression.alias()`
construct generated.
:param cast_nulls: if True, non-existent columns, which are represented as labeled
NULLs, will be passed into CAST. This is a legacy behavior that is problematic
on some backends such as Oracle - in which case it can be set to False.
"""
colnames = util.OrderedSet()
colnamemaps = {}
types = {}
for key in table_map.keys():
table = table_map[key]
# mysql doesnt like selecting from a select;
# make it an alias of the select
if isinstance(table, sql.Select):
table = table.alias()
table_map[key] = table
m = {}
for c in table.c:
colnames.add(c.key)
m[c.key] = c
types[c.key] = c.type
colnamemaps[table] = m
def col(name, table):
try:
return colnamemaps[table][name]
except KeyError:
if cast_nulls:
return sql.cast(sql.null(), types[name]).label(name)
else:
return sql.type_coerce(sql.null(), types[name]).label(name)
result = []
for type, table in table_map.iteritems():
if typecolname is not None:
result.append(
sql.select(
[col(name, table) for name in colnames]
+ [sql.literal_column(sql_util._quote_ddl_expr(type)).label(typecolname)],
from_obj=[table],
)
)
else:
result.append(sql.select([col(name, table) for name in colnames], from_obj=[table]))
return sql.union_all(*result).alias(aliasname)
def polymorphic_union(table_map, typecolname, aliasname='p_union', cast_nulls=True):
"""Create a ``UNION`` statement used by a polymorphic mapper.
See :ref:`concrete_inheritance` for an example of how
this is used.
:param table_map: mapping of polymorphic identities to
:class:`.Table` objects.
:param typecolname: string name of a "discriminator" column, which will be
derived from the query, producing the polymorphic identity for each row. If
``None``, no polymorphic discriminator is generated.
:param aliasname: name of the :func:`~sqlalchemy.sql.expression.alias()`
construct generated.
:param cast_nulls: if True, non-existent columns, which are represented as labeled
NULLs, will be passed into CAST. This is a legacy behavior that is problematic
on some backends such as Oracle - in which case it can be set to False.
"""
colnames = util.OrderedSet()
colnamemaps = {}
types = {}
for key in list(table_map.keys()):
table = table_map[key]
# mysql doesnt like selecting from a select;
# make it an alias of the select
if isinstance(table, sql.Select):
table = table.alias()
table_map[key] = table
m = {}
for c in table.c:
colnames.add(c.key)
m[c.key] = c
types[c.key] = c.type
colnamemaps[table] = m
def col(name, table):
try:
return colnamemaps[table][name]
except KeyError:
if cast_nulls:
return sql.cast(sql.null(), types[name]).label(name)
else:
return sql.type_coerce(sql.null(), types[name]).label(name)
result = []
for type, table in table_map.items():
if typecolname is not None:
result.append(
sql.select([col(name, table) for name in colnames] +
[sql.literal_column(sql_util._quote_ddl_expr(type)).
label(typecolname)],
from_obj=[table]))
else:
result.append(sql.select([col(name, table) for name in colnames],
from_obj=[table]))
return sql.union_all(*result).alias(aliasname)
def polymorphic_union(table_map, typecolname, aliasname='p_union'):
"""Create a ``UNION`` statement used by a polymorphic mapper.
See :ref:`concrete_inheritance` for an example of how
this is used.
"""
colnames = set()
colnamemaps = {}
types = {}
for key in table_map.keys():
table = table_map[key]
# mysql doesnt like selecting from a select;
# make it an alias of the select
if isinstance(table, sql.Select):
table = table.alias()
table_map[key] = table
m = {}
for c in table.c:
colnames.add(c.key)
m[c.key] = c
types[c.key] = c.type
colnamemaps[table] = m
def col(name, table):
try:
return colnamemaps[table][name]
except KeyError:
return sql.cast(sql.null(), types[name]).label(name)
result = []
for type, table in table_map.iteritems():
if typecolname is not None:
result.append(
sql.select([col(name, table) for name in colnames] + [
sql.literal_column(
sql_util._quote_ddl_expr(type)).label(typecolname)
],
from_obj=[table]))
else:
result.append(
sql.select([col(name, table) for name in colnames],
from_obj=[table]))
return sql.union_all(*result).alias(aliasname)
def polymorphic_union(table_map, typecolname, aliasname='p_union'):
"""Create a ``UNION`` statement used by a polymorphic mapper.
See :ref:`concrete_inheritance` for an example of how
this is used.
"""
colnames = set()
colnamemaps = {}
types = {}
for key in table_map.keys():
table = table_map[key]
# mysql doesnt like selecting from a select;
# make it an alias of the select
if isinstance(table, sql.Select):
table = table.alias()
table_map[key] = table
m = {}
for c in table.c:
colnames.add(c.key)
m[c.key] = c
types[c.key] = c.type
colnamemaps[table] = m
def col(name, table):
try:
return colnamemaps[table][name]
except KeyError:
return sql.cast(sql.null(), types[name]).label(name)
result = []
for type, table in table_map.iteritems():
if typecolname is not None:
result.append(
sql.select([col(name, table) for name in colnames] +
[sql.literal_column(sql_util._quote_ddl_expr(type)).
label(typecolname)],
from_obj=[table]))
else:
result.append(sql.select([col(name, table) for name in colnames],
from_obj=[table]))
return sql.union_all(*result).alias(aliasname)
