server/tag-categories: fix default categories

- Don't cache default category in its entirety - cache only its name
- Purge cache on category name changes and default category changes
- Lock records for updates where applicable

server/szurubooru/api/tag_category_api.py

@@ -40,7 +40,8 @@ def get_tag_category(ctx, params):
 
 @routes.put('/tag-category/(?P<category_name>[^/]+)/?')
 def update_tag_category(ctx, params):
-    category = tag_categories.get_category_by_name(params['category_name'])
+    category = tag_categories.get_category_by_name(
+        params['category_name'], lock=True)
     versions.verify_version(category, ctx)
     versions.bump_version(category)
     if ctx.has_param('name'):
@@ -60,7 +61,8 @@ def update_tag_category(ctx, params):
 
 @routes.delete('/tag-category/(?P<category_name>[^/]+)/?')
 def delete_tag_category(ctx, params):
-    category = tag_categories.get_category_by_name(params['category_name'])
+    category = tag_categories.get_category_by_name(
+        params['category_name'], lock=True)
     versions.verify_version(category, ctx)
     auth.verify_privilege(ctx.user, 'tag_categories:delete')
     tag_categories.delete_category(category)
@@ -73,8 +75,10 @@ def delete_tag_category(ctx, params):
 @routes.put('/tag-category/(?P<category_name>[^/]+)/default/?')
 def set_tag_category_as_default(ctx, params):
     auth.verify_privilege(ctx.user, 'tag_categories:set_default')
-    category = tag_categories.get_category_by_name(params['category_name'])
+    category = tag_categories.get_category_by_name(
+        params['category_name'], lock=True)
     tag_categories.set_default_category(category)
+    ctx.session.flush()
     snapshots.modify(category, ctx.user)
     ctx.session.commit()
     tags.export_to_json()

server/szurubooru/func/cache.py

@@ -55,5 +55,10 @@ def get(key):
     return _CACHE.hash[key].value
 
 
+def remove(key):
+    if has(key):
+        del _CACHE.hash[key]
+
+
 def put(key, value):
     _CACHE.insert_item(LruCacheItem(key, value))

server/szurubooru/func/tag_categories.py

@@ -4,6 +4,9 @@ from szurubooru import config, db, errors
 from szurubooru.func import util, cache
 
 
+DEFAULT_CATEGORY_NAME_CACHE_KEY = 'default-tag-category'
+
+
 class TagCategoryNotFoundError(errors.NotFoundError):
     pass
 
@@ -69,6 +72,7 @@ def update_category_name(category, name):
         raise InvalidTagCategoryNameError('Name is too long.')
     _verify_name_validity(name)
     category.name = name
+    cache.remove(DEFAULT_CATEGORY_NAME_CACHE_KEY)
 
 
 def update_category_color(category, color):
@@ -82,15 +86,17 @@ def update_category_color(category, color):
     category.color = color
 
 
-def try_get_category_by_name(name):
+def try_get_category_by_name(name, lock=False):
-    return db.session \
+    query = db.session \
         .query(db.TagCategory) \
-        .filter(sqlalchemy.func.lower(db.TagCategory.name) == name.lower()) \
+        .filter(sqlalchemy.func.lower(db.TagCategory.name) == name.lower())
-        .one_or_none()
+    if lock:
+        query = query.with_lockmode('update')
+    return query.one_or_none()
 
 
-def get_category_by_name(name):
+def get_category_by_name(name, lock=False):
-    category = try_get_category_by_name(name)
+    category = try_get_category_by_name(name, lock)
     if not category:
         raise TagCategoryNotFoundError('Tag category %r not found.' % name)
     return category
@@ -104,38 +110,50 @@ def get_all_categories():
     return db.session.query(db.TagCategory).all()
 
 
-def try_get_default_category():
+def try_get_default_category(lock=False):
-    key = 'default-tag-category'
+    query = db.session \
-    if cache.has(key):
-        return cache.get(key)
-    category = db.session \
         .query(db.TagCategory) \
-        .filter(db.TagCategory.default) \
+        .filter(db.TagCategory.default)
-        .first()
+    if lock:
+        query = query.with_lockmode('update')
+    category = query.first()
     # if for some reason (e.g. as a result of migration) there's no default
     # category, get the first record available.
     if not category:
-        category = db.session \
+        query = db.session \
             .query(db.TagCategory) \
-            .order_by(db.TagCategory.tag_category_id.asc()) \
+            .order_by(db.TagCategory.tag_category_id.asc())
-            .first()
+        if lock:
-    cache.put(key, category)
+            query = query.with_lockmode('update')
+        category = query.first()
     return category
 
 
-def get_default_category():
+def get_default_category(lock=False):
-    category = try_get_default_category()
+    category = try_get_default_category(lock)
     if not category:
         raise TagCategoryNotFoundError('No tag category created yet.')
     return category
 
 
+def get_default_category_name():
+    if cache.has(DEFAULT_CATEGORY_NAME_CACHE_KEY):
+        return cache.get(DEFAULT_CATEGORY_NAME_CACHE_KEY)
+    default_category = try_get_default_category()
+    default_category_name = default_category.name if default_category else None
+    cache.put(DEFAULT_CATEGORY_NAME_CACHE_KEY, default_category_name)
+    return default_category_name
+
+
 def set_default_category(category):
     assert category
-    old_category = try_get_default_category()
+    old_category = try_get_default_category(lock=True)
     if old_category:
+        db.session.refresh(old_category)
         old_category.default = False
+    db.session.refresh(category)
     category.default = True
+    cache.remove(DEFAULT_CATEGORY_NAME_CACHE_KEY)
 
 
 def delete_category(category):

server/szurubooru/func/tags.py

@@ -58,8 +58,7 @@ def _check_name_intersection(names1, names2, case_sensitive):
 
 
 def sort_tags(tags):
-    default_category = tag_categories.try_get_default_category()
+    default_category_name = tag_categories.get_default_category_name()
-    default_category_name = default_category.name if default_category else None
     return sorted(
         tags,
         key=lambda tag: (
@@ -170,7 +169,7 @@ def get_or_create_tags_by_names(names):
     names = util.icase_unique(names)
     existing_tags = get_tags_by_names(names)
     new_tags = []
-    tag_category_name = tag_categories.get_default_category().name
+    tag_category_name = tag_categories.get_default_category_name()
     for name in names:
         found = False
         for existing_tag in existing_tags:

server/szurubooru/tests/func/test_tag_categories.py

@@ -181,16 +181,32 @@ def test_try_get_default_category_when_default(tag_category_factory):
     assert actual_default_category != category1
 
 
-def test_try_get_default_category_from_cache(tag_category_factory):
+def test_get_default_category_name(tag_category_factory):
+    category1 = tag_category_factory()
+    category2 = tag_category_factory(default=True)
+    db.session.add_all([category1, category2])
+    db.session.flush()
+    assert tag_categories.get_default_category_name() == category2.name
+    category2.default = False
+    db.session.flush()
+    cache.purge()
+    assert tag_categories.get_default_category_name() == category1.name
+    db.session.query(db.TagCategory).delete()
+    cache.purge()
+    assert tag_categories.get_default_category_name() is None
+
+
+def test_get_default_category_name_caching(tag_category_factory):
     category1 = tag_category_factory()
     category2 = tag_category_factory()
     db.session.add_all([category1, category2])
     db.session.flush()
-    tag_categories.try_get_default_category()
+    tag_categories.get_default_category_name()
-    db.session.query(db.TagCategory).delete()
+    db.session.delete(category1)
-    assert tag_categories.try_get_default_category() == category1
+    db.session.flush()
+    assert tag_categories.get_default_category_name() == category1.name
     cache.purge()
-    assert tag_categories.try_get_default_category() is None
+    assert tag_categories.get_default_category_name() == category2.name
 
 
 def test_get_default_category():