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Fixed #13724: Corrected routing of write queries involving managers.

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Previously, if a database request spanned a related object manager, the
first manager encountered would cause a request to the router, and this
would bind all subsequent queries to the same database returned by the
router. Unfortunately, the first router query would be performed using
a read request to the router, resulting in bad routing information being
used if the subsequent query was actually a write.

This change defers the call to the router until the final query is acutally
made.

It includes a small *BACKWARDS INCOMPATIBILITY* on an edge case - see the
release notes for details.

Thanks to Paul Collins (@paulcollinsiii) for the excellent debugging
work and patch.
This commit is contained in:
Russell Keith-Magee 2013-09-30 13:05:43 +08:00
parent 12ca312e1b
commit 9595183d03
5 changed files with 303 additions and 24 deletions
Download patch file Download diff file Expand all files Collapse all files

22
django/db/models/query.py
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@ -47,9 +47,10 @@ class QuerySet(object):
Represents a lazy database lookup for a set of objects.
"""
def __init__(self, model=None, query=None, using=None):
def __init__(self, model=None, query=None, using=None, hints=None):
self.model = model
self._db = using
self._hints = hints or {}
self.query = query or sql.Query(self.model)
self._result_cache = None
self._sticky_filter = False
@ -904,8 +905,8 @@ class QuerySet(object):
def db(self):
"Return the database that will be used if this query is executed now"
if self._for_write:
return self._db or router.db_for_write(self.model)
return self._db or router.db_for_read(self.model)
return self._db or router.db_for_write(self.model, **self._hints)
return self._db or router.db_for_read(self.model, **self._hints)
###################
# PRIVATE METHODS #
@ -955,7 +956,7 @@ class QuerySet(object):
query = self.query.clone()
if self._sticky_filter:
query.filter_is_sticky = True
c = klass(model=self.model, query=query, using=self._db)
c = klass(model=self.model, query=query, using=self._db, hints=self._hints)
c._for_write = self._for_write
c._prefetch_related_lookups = self._prefetch_related_lookups[:]
c._known_related_objects = self._known_related_objects
@ -1025,6 +1026,14 @@ class QuerySet(object):
# empty" result.
value_annotation = True
def _add_hints(self, **hints):
"""
Update hinting information for later use by Routers
"""
# If there is any hinting information, add it to what we already know.
# If we have a new hint for an existing key, overwrite with the new value.
self._hints.update(hints)
class InstanceCheckMeta(type):
def __instancecheck__(self, instance):
@ -1485,10 +1494,11 @@ class RawQuerySet(object):
annotated model instances.
"""
def __init__(self, raw_query, model=None, query=None, params=None,
translations=None, using=None):
translations=None, using=None, hints=None):
self.raw_query = raw_query
self.model = model
self._db = using
self._hints = hints or {}
self.query = query or sql.RawQuery(sql=raw_query, using=self.db, params=params)
self.params = params or ()
self.translations = translations or {}
@ -1572,7 +1582,7 @@ class RawQuerySet(object):
@property
def db(self):
"Return the database that will be used if this query is executed now"
return self._db or router.db_for_read(self.model)
return self._db or router.db_for_read(self.model, **self._hints)
def using(self, alias):
"""