#35967: TransactionTestCase.serialized_rollback reads from real database rather
than test when using read replica for a model instance created in a
migration with a ManyToManyField
-------------------------------------+-------------------------------------
Reporter: Jake Howard | Owner: Jacob
| Walls
Type: Bug | Status: assigned
Component: Core | Version: dev
(Serialization) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Simon Charette):
> If someone more knowledgable can opine on correctness and backwards
compatibility, I'm happy to push this forward.
Hey Jacob I admittedly haven't looked into the issue in depth but I think
that forcing the usage of the current alias like you did here is a
certainly a key towards the solution.
I have a hunch that the actual problems lives in
`djang.test.utils.setup_databases` though and particularly how
`BaseDatabaseCreation.create_test_db` is implemented. `setup_databases`
currently follows this sequence of operations for each `DATABASES` entries
1. Create the test db replacement
2. Repoint `settings.DATABASES[alias][name]` to the test db replacement
3. Peform migrations
4. Serialize content
I think that instead what it should do is 1, 2, 3 for each `DATABASES`
entries (making sure that all the test databases are setup) and then do 4
for each of them. Something like
{{{#!diff
diff --git a/django/db/backends/base/creation.py
b/django/db/backends/base/creation.py
index 6856fdb596..7a0e2a0622 100644
--- a/django/db/backends/base/creation.py
+++ b/django/db/backends/base/creation.py
@@ -91,6 +91,7 @@ def create_test_db(
# who are testing on databases without transactions or who are
using
# a TransactionTestCase still get a clean database on every test
run.
if serialize:
+ # XXX: Emit a deprecation warnings when `serialize` is
provided.
self.connection._test_serialized_contents =
self.serialize_db_to_string()
call_command("createcachetable", database=self.connection.alias)
diff --git a/django/test/utils.py b/django/test/utils.py
index ddb85127dc..a2fe8b14cc 100644
--- a/django/test/utils.py
+++ b/django/test/utils.py
@@ -189,6 +189,7 @@ def setup_databases(
test_databases, mirrored_aliases =
get_unique_databases_and_mirrors(aliases)
old_names = []
+ serialize_connections = []
for db_name, aliases in test_databases.values():
first_alias = None
@@ -200,15 +201,13 @@ def setup_databases(
if first_alias is None:
first_alias = alias
with time_keeper.timed(" Creating '%s'" % alias):
- serialize_alias = (
- serialized_aliases is None or alias in
serialized_aliases
- )
connection.creation.create_test_db(
verbosity=verbosity,
autoclobber=not interactive,
keepdb=keepdb,
- serialize=serialize_alias,
)
+ if serialized_aliases is None or alias in
serialized_aliases:
+ serialize_connections.append(connection)
if parallel > 1:
for index in range(parallel):
with time_keeper.timed(" Cloning '%s'" % alias):
@@ -223,6 +222,13 @@ def setup_databases(
connections[first_alias].settings_dict
)
+ # Serialize content of test databases only once all of them are setup
+ # to account for database routing during serialization.
+ for serialize_connection in serialize_connections:
+ serialize_connection._test_serialized_contents = (
+ serialize_connection.serialize_db_to_string()
+ )
+
# Configure the test mirrors.
for alias, mirror_alias in mirrored_aliases.items():
connections[alias].creation.set_as_test_mirror(
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/35967#comment:5>
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