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from django.db.models.sql.constants import INNER
class QJoin:
"""Join clause with join condition from Q object clause
:param parent_alias: Alias of parent table.
:param table_name: Name of joined table.
:param table_alias: Alias of joined table.
:param on_clause: Query `where_class` instance represenging the ON clause.
:param join_type: Join type (INNER or LOUTER).
"""
filtered_relation = None
def __init__(self, parent_alias, table_name, table_alias,
on_clause, join_type=INNER, nullable=None):
self.parent_alias = parent_alias
self.table_name = table_name
self.table_alias = table_alias
self.on_clause = on_clause
self.join_type = join_type # LOUTER or INNER
self.nullable = join_type != INNER if nullable is None else nullable
@property
def identity(self):
return (
self.__class__,
self.table_name,
self.parent_alias,
self.join_type,
self.on_clause,
)
def __hash__(self):
return hash(self.identity)
def __eq__(self, other):
if not isinstance(other, QJoin):
return NotImplemented
return self.identity == other.identity
def equals(self, other):
return self.identity == other.identity
def as_sql(self, compiler, connection):
"""Generate join clause SQL"""
on_clause_sql, params = self.on_clause.as_sql(compiler, connection)
if self.table_alias == self.table_name:
alias = ''
else:
alias = ' %s' % self.table_alias
qn = compiler.quote_name_unless_alias
sql = '%s %s%s ON %s' % (
self.join_type,
qn(self.table_name),
alias,
on_clause_sql
)
return sql, params
def relabeled_clone(self, change_map):
return self.__class__(
parent_alias=change_map.get(self.parent_alias, self.parent_alias),
table_name=self.table_name,
table_alias=change_map.get(self.table_alias, self.table_alias),
on_clause=self.on_clause.relabeled_clone(change_map),
join_type=self.join_type,
nullable=self.nullable,
)
class join_field:
# `Join.join_field` is used internally by `Join` as well as in
# `QuerySet.resolve_expression()`:
#
# isinstance(table, Join)
# and table.join_field.related_model._meta.db_table != alias
#
# Currently that does not apply here since `QJoin` is not an
# instance of `Join`, although maybe it should? Maybe this
# should have `related_model._meta.db_table` return
# `<QJoin>.table_name` or `<QJoin>.table_alias`?
#
# `PathInfo.join_field` is another similarly named attribute in
# Django that has a much more complicated interface, but luckily
# seems unrelated to `Join.join_field`.
class related_model:
class _meta:
# for QuerySet.set_group_by(allow_aliases=True)
local_concrete_fields = ()
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