perf: User delete - deletion handler veto improvement [DHIS2-21725]

[david-mackessy]

Performance improvement

Change FlushMode from AUTO (default) to COMMIT in HibernateIdentifiableObjectStore.existsByUser

• removes needless dirty checks during user deletes
• checks were being run for every entity being checked for user association
• deletion VETOs run first during user delete, so already reading from a correct state (no writes earlier in transaction)
• only 1 caller of this method - IdObjectDeletionHandler.allowDeleteUser

2 existing tests now need flush before assertions to ensure reading correct state.

Tests

Local performance tests run show times almost halved

• P95 ~1.4s -> ~0.8s
• this includes the platform-perf DB having the following data associated with users to ensure that deletion handlers are exercised.

Data	Table(s)	per user	Handler exercised
User settings	usersetting	15	UserSettingDeletionHandler
Datastore entries	userkeyjsonvalue	15	UserDatastoreDeletionHandler
Data-view OUs	userdatavieworgunits	10	cascade cleanup
TEI-search OUs	userteisearchorgunits	10	cascade cleanup
Previous passwords	previouspasswords	3	cascade cleanup
Interpretations	interpretation	5	InterpretationDeletionHandler (null-out)
Messages	messageconversation +3	5	message handler (sender/recipient)
Dashboard items	dashboarditem +_users	5	DashboardItemDeletionHandler

Next

• User performance test will be updated to reflect new version of platform-perf DB with User data for deletion handler triggers
• Upload new version of platform-perf DB with user deletion handler data

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud