• Yorick Peterse's avatar
    Use CTEs for nested groups and authorizations · ac382b56
    Yorick Peterse authored
    This commit introduces the usage of Common Table Expressions (CTEs) to
    efficiently retrieve nested group hierarchies, without having to rely on
    the "routes" table (which is an _incredibly_ inefficient way of getting
    the data). This requires a patch to ActiveRecord (found in the added
    initializer) to work properly as ActiveRecord doesn't support WITH
    statements properly out of the box.
    
    Unfortunately MySQL provides no efficient way of getting nested groups.
    For example, the old routes setup could easily take 5-10 seconds
    depending on the amount of "routes" in a database. Providing vastly
    different logic for both MySQL and PostgreSQL will negatively impact the
    development process. Because of this the various nested groups related
    methods return empty relations when used in combination with MySQL.
    
    For project authorizations the logic is split up into two classes:
    
    * Gitlab::ProjectAuthorizations::WithNestedGroups
    * Gitlab::ProjectAuthorizations::WithoutNestedGroups
    
    Both classes get the fresh project authorizations (= as they should be
    in the "project_authorizations" table), including nested groups if
    PostgreSQL is used. The logic of these two classes is quite different
    apart from their public interface. This complicates development a bit,
    but unfortunately there is no way around this.
    
    This commit also introduces Gitlab::GroupHierarchy. This class can be
    used to get the ancestors and descendants of a base relation, or both by
    using a UNION. This in turn is used by methods such as:
    
    * Namespace#ancestors
    * Namespace#descendants
    * User#all_expanded_groups
    
    Again this class relies on CTEs and thus only works on PostgreSQL. The
    Namespace methods will return an empty relation when MySQL is used,
    while User#all_expanded_groups will return only the groups a user is a
    direct member of.
    
    Performance wise the impact is quite large. For example, on GitLab.com
    Namespace#descendants used to take around 580 ms to retrieve data for a
    particular user. Using CTEs we are able to reduce this down to roughly 1
    millisecond, returning the exact same data.
    
    == On The Fly Refreshing
    
    Refreshing of authorizations on the fly (= when
    users.authorized_projects_populated was not set) is removed with this
    commit. This simplifies the code, and ensures any queries used for
    authorizations are not mutated because they are executed in a Rails
    scope (e.g. Project.visible_to_user).
    
    This commit includes a migration to schedule refreshing authorizations
    for all users, ensuring all of them have their authorizations in place.
    Said migration schedules users in batches of 5000, with 5 minutes
    between every batch to smear the load around a bit.
    
    == Spec Changes
    
    This commit also introduces some changes to various specs. For example,
    some specs for ProjectTeam assumed that creating a personal project
    would _not_ lead to the owner having access, which is incorrect. Because
    we also no longer refresh authorizations on the fly for new users some
    code had to be added to the "empty_project" factory. This chunk of code
    ensures that the owner's permissions are refreshed after creating the
    project, something that is normally done in Projects::CreateService.
    ac382b56
20170503120310_remove_users_authorized_projects_populated.rb 455 Bytes