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Diffstat (limited to 'lib/gitlab/group_hierarchy.rb')
-rw-r--r-- | lib/gitlab/group_hierarchy.rb | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/lib/gitlab/group_hierarchy.rb b/lib/gitlab/group_hierarchy.rb new file mode 100644 index 00000000000..e9d5d52cabb --- /dev/null +++ b/lib/gitlab/group_hierarchy.rb @@ -0,0 +1,104 @@ +module Gitlab + # Retrieving of parent or child groups based on a base ActiveRecord relation. + # + # This class uses recursive CTEs and as a result will only work on PostgreSQL. + class GroupHierarchy + attr_reader :base, :model + + # base - An instance of ActiveRecord::Relation for which to get parent or + # child groups. + def initialize(base) + @base = base + @model = base.model + end + + # Returns a relation that includes the base set of groups and all their + # ancestors (recursively). + def base_and_ancestors + return model.none unless Group.supports_nested_groups? + + base_and_ancestors_cte.apply_to(model.all) + end + + # Returns a relation that includes the base set of groups and all their + # descendants (recursively). + def base_and_descendants + return model.none unless Group.supports_nested_groups? + + base_and_descendants_cte.apply_to(model.all) + end + + # Returns a relation that includes the base groups, their ancestors, and the + # descendants of the base groups. + # + # The resulting query will roughly look like the following: + # + # WITH RECURSIVE ancestors AS ( ... ), + # descendants AS ( ... ) + # SELECT * + # FROM ( + # SELECT * + # FROM ancestors namespaces + # + # UNION + # + # SELECT * + # FROM descendants namespaces + # ) groups; + # + # Using this approach allows us to further add criteria to the relation with + # Rails thinking it's selecting data the usual way. + def all_groups + return base unless Group.supports_nested_groups? + + ancestors = base_and_ancestors_cte + descendants = base_and_descendants_cte + + ancestors_table = ancestors.alias_to(groups_table) + descendants_table = descendants.alias_to(groups_table) + + union = SQL::Union.new([model.unscoped.from(ancestors_table), + model.unscoped.from(descendants_table)]) + + model. + unscoped. + with. + recursive(ancestors.to_arel, descendants.to_arel). + from("(#{union.to_sql}) #{model.table_name}") + end + + private + + def base_and_ancestors_cte + cte = SQL::RecursiveCTE.new(:base_and_ancestors) + + cte << base.except(:order) + + # Recursively get all the ancestors of the base set. + cte << model. + from([groups_table, cte.table]). + where(groups_table[:id].eq(cte.table[:parent_id])). + except(:order) + + cte + end + + def base_and_descendants_cte + cte = SQL::RecursiveCTE.new(:base_and_descendants) + + cte << base.except(:order) + + # Recursively get all the descendants of the base set. + cte << model. + from([groups_table, cte.table]). + where(groups_table[:parent_id].eq(cte.table[:id])). + except(:order) + + cte + end + + def groups_table + model.arel_table + end + end +end |