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  1. 17 Sep, 2018 1 commit
    • Yorick Peterse's avatar
      Added FromUnion to easily select from a UNION · 84f6b869d148
      Yorick Peterse authored
      This commit adds the module `FromUnion`, which provides the class method
      `from_union`. This simplifies the process of selecting data from the
      result of a UNION, and reduces the likelihood of making mistakes. As a
      result, instead of this:
      
          union = Gitlab::SQL::Union.new([foo, bar])
      
          Foo.from("(#{union.to_sql}) #{Foo.table_name}")
      
      We can now write this instead:
      
          Foo.from_union([foo, bar])
      
      This commit also includes some changes to make this new setup work
      properly. For example, a bug in Rails 4
      (https://github.com/rails/rails/issues/24193) would break the use of
      `from("sub-query-here").includes(:relation)` in certain cases. There was
      also a CI query which appeared to repeat a lot of conditions from an
      outer query on an inner query, which isn't necessary.
      
      Finally, we include a RuboCop cop to ensure developers use this new
      module, instead of using Gitlab::SQL::Union directly.
      
      Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/51307
      84f6b869d148
  2. 26 Jul, 2018 1 commit
  3. 21 Jun, 2017 1 commit
  4. 17 May, 2017 1 commit
    • Yorick Peterse's avatar
      Use CTEs for nested groups and authorizations · f63dad32f25f
      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.
      f63dad32f25f
  5. 19 Dec, 2016 1 commit
    • Yorick Peterse's avatar
      Smarter refreshing of authorized projects · 94b6f1e51113
      Yorick Peterse authored
      Prior to this commit the refreshing of authorized projects was done in
      two steps:
      
      1. Remove existing authorizations
      2. Insert a new list of all authorizations
      
      This can lead to a high amount of dead tuples as every time all rows are
      being replaced. For example, if a user with 100 authorizations is given
      access to a new project this would lead to:
      
      * 100 rows being removed
      * 101 new rows being inserted
      
      This commit changes the way this system works so it only removes/inserts
      what is necessary. Using the above example this would lead to only 1 new
      row being inserted, with the initial 100 being left untouched.
      
      Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/25257
      94b6f1e51113
  6. 18 Nov, 2016 1 commit