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queryset-refactor: Added a way to change the prefix of all aliases in a query.

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This fixes the last few corner cases for nested queries that had overlapping
aliases. Also tidies up a couple of internal data structures.


git-svn-id: http://code.djangoproject.com/svn/django/branches/queryset-refactor@7231 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Malcolm Tredinnick 2008-03-12 14:52:12 +00:00
parent 428450b7a9
commit c8b33b824b
2 changed files with 53 additions and 37 deletions
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87
django/db/models/sql/query.py
View File

@ -44,7 +44,6 @@ class Query(object):
self.connection = connection
self.alias_map = {} # Maps alias to table name
self.table_map = {} # Maps table names to list of aliases.
self.join_map = {} # Maps join_tuple to list of aliases.
self.rev_join_map = {} # Reverse of join_map.
self.quote_cache = {}
self.default_cols = True
@ -128,8 +127,7 @@ class Query(object):
obj.connection = self.connection
obj.alias_map = copy.deepcopy(self.alias_map)
obj.table_map = self.table_map.copy()
obj.join_map = copy.deepcopy(self.join_map)
obj.rev_join_map = copy.deepcopy(self.rev_join_map)
obj.rev_join_map = self.rev_join_map.copy()
obj.quote_cache = {}
obj.default_cols = self.default_cols
obj.default_ordering = self.default_ordering
@ -584,42 +582,65 @@ class Query(object):
if self.alias_map[alias][ALIAS_NULLABLE]:
self.alias_map[alias][ALIAS_JOIN][JOIN_TYPE] = self.LOUTER
def change_alias(self, old_alias, new_alias):
def change_aliases(self, change_map):
"""
Changes old_alias to new_alias, relabelling any references to it in
select columns and the where clause.
Changes the aliases in change_map (which maps old-alias -> new-alias),
relabelling any references to them in select columns and the where
clause.
"""
assert new_alias not in self.alias_map
assert set(change_map.keys()).intersection(set(change_map.values())) == set()
# 1. Update references in "select" and "where".
change_map = {old_alias: new_alias}
self.where.relabel_aliases(change_map)
for pos, col in enumerate(self.select):
if isinstance(col, (list, tuple)):
if col[0] == old_alias:
self.select[pos] = (new_alias, col[1])
self.select[pos] = (change_map.get(old_alias, old_alias), col[1])
else:
col.relabel_aliases(change_map)
# 2. Rename the alias in the internal table/alias datastructures.
alias_data = self.alias_map[old_alias]
alias_data[ALIAS_JOIN][RHS_ALIAS] = new_alias
table_aliases = self.table_map[alias_data[ALIAS_TABLE]]
for pos, alias in enumerate(table_aliases):
if alias == old_alias:
table_aliases[pos] = new_alias
break
self.alias_map[new_alias] = alias_data
del self.alias_map[old_alias]
for pos, alias in enumerate(self.tables):
if alias == old_alias:
self.tables[pos] = new_alias
break
for old_alias, new_alias in change_map.items():
alias_data = self.alias_map[old_alias]
alias_data[ALIAS_JOIN][RHS_ALIAS] = new_alias
self.rev_join_map[new_alias] = self.rev_join_map[old_alias]
del self.rev_join_map[old_alias]
table_aliases = self.table_map[alias_data[ALIAS_TABLE]]
for pos, alias in enumerate(table_aliases):
if alias == old_alias:
table_aliases[pos] = new_alias
break
self.alias_map[new_alias] = alias_data
del self.alias_map[old_alias]
for pos, alias in enumerate(self.tables):
if alias == old_alias:
self.tables[pos] = new_alias
break
# 3. Update any joins that refer to the old alias.
for data in self.alias_map.values():
if data[ALIAS_JOIN][LHS_ALIAS] == old_alias:
data[ALIAS_JOIN][LHS_ALIAS] = new_alias
alias = data[ALIAS_JOIN][LHS_ALIAS]
if alias in change_map:
data[ALIAS_JOIN][LHS_ALIAS] = change_map[alias]
def bump_prefix(self):
"""
Changes the alias prefix to the next letter in the alphabet and
relabels all the aliases. Even tables that previously had no alias will
get an alias after this call (it's mostly used for nested queries and
the outer query will already be using the non-aliased table name).
Subclasses who create their own prefix should override this method to
produce a similar result (a new prefix and relabelled aliases).
"""
assert ord(self.alias_prefix) < ord('Z')
self.alias_prefix = chr(ord(self.alias_prefix) + 1)
change_map = {}
prefix = self.alias_prefix
for pos, alias in enumerate(self.tables):
new_alias = '%s%d' % (prefix, pos)
change_map[alias] = new_alias
self.tables[pos] = new_alias
self.change_aliases(change_map)
def get_initial_alias(self):
"""
@ -681,15 +702,12 @@ class Query(object):
is_table = False
t_ident = (lhs_table, table, lhs_col, col)
if not always_create:
aliases = self.join_map.get(t_ident)
if aliases:
for alias in aliases:
if alias not in exclusions:
self.ref_alias(alias)
if promote and self.alias_map[alias][ALIAS_NULLABLE]:
self.alias_map[alias][ALIAS_JOIN][JOIN_TYPE] = \
self.LOUTER
return alias
for alias, row in self.rev_join_map.items():
if t_ident == row and alias not in exclusions:
self.ref_alias(alias)
if promote and self.alias_map[alias][ALIAS_NULLABLE]:
self.alias_map[alias][ALIAS_JOIN][JOIN_TYPE] = self.LOUTER
return alias
# If we get to here (no non-excluded alias exists), we'll fall
# through to creating a new alias.
@ -708,7 +726,6 @@ class Query(object):
join[JOIN_TYPE] = None
self.alias_map[alias][ALIAS_JOIN] = join
self.alias_map[alias][ALIAS_NULLABLE] = nullable
self.join_map.setdefault(t_ident, []).append(alias)
self.rev_join_map[alias] = t_ident
return alias

3
django/db/models/sql/subqueries.py
View File

@ -158,8 +158,7 @@ class UpdateQuery(Query):
# We need to use a sub-select in the where clause to filter on things
# from other tables.
query = self.clone(klass=Query)
alias = '%s0' % self.alias_prefix
query.change_alias(query.tables[0], alias)
query.bump_prefix()
self.add_fields([query.model._meta.pk.name])
# Now we adjust the current query: reset the where clause and get rid