154 lines
5 KiB
Ruby
154 lines
5 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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# Retrieving of parent or child groups based on a base ActiveRecord relation.
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#
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# This class uses recursive CTEs and as a result will only work on PostgreSQL.
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class GroupHierarchy
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attr_reader :ancestors_base, :descendants_base, :model
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# ancestors_base - An instance of ActiveRecord::Relation for which to
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# get parent groups.
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# descendants_base - An instance of ActiveRecord::Relation for which to
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# get child groups. If omitted, ancestors_base is used.
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def initialize(ancestors_base, descendants_base = ancestors_base)
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raise ArgumentError.new("Model of ancestors_base does not match model of descendants_base") if ancestors_base.model != descendants_base.model
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@ancestors_base = ancestors_base
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@descendants_base = descendants_base
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@model = ancestors_base.model
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end
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# Returns the set of descendants of a given relation, but excluding the given
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# relation
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# rubocop: disable CodeReuse/ActiveRecord
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def descendants
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base_and_descendants.where.not(id: descendants_base.select(:id))
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end
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# rubocop: enable CodeReuse/ActiveRecord
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# Returns the set of ancestors of a given relation, but excluding the given
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# relation
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#
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# Passing an `upto` will stop the recursion once the specified parent_id is
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# reached. So all ancestors *lower* than the specified ancestor will be
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# included.
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# rubocop: disable CodeReuse/ActiveRecord
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def ancestors(upto: nil)
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base_and_ancestors(upto: upto).where.not(id: ancestors_base.select(:id))
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end
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# rubocop: enable CodeReuse/ActiveRecord
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# Returns a relation that includes the ancestors_base set of groups
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# and all their ancestors (recursively).
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#
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# Passing an `upto` will stop the recursion once the specified parent_id is
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# reached. So all ancestors *lower* than the specified acestor will be
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# included.
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def base_and_ancestors(upto: nil)
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return ancestors_base unless Group.supports_nested_groups?
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read_only(base_and_ancestors_cte(upto).apply_to(model.all))
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end
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# Returns a relation that includes the descendants_base set of groups
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# and all their descendants (recursively).
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def base_and_descendants
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return descendants_base unless Group.supports_nested_groups?
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read_only(base_and_descendants_cte.apply_to(model.all))
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end
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# Returns a relation that includes the base groups, their ancestors,
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# and the descendants of the base groups.
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#
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# The resulting query will roughly look like the following:
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#
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# WITH RECURSIVE ancestors AS ( ... ),
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# descendants AS ( ... )
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# SELECT *
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# FROM (
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# SELECT *
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# FROM ancestors namespaces
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#
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# UNION
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#
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# SELECT *
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# FROM descendants namespaces
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# ) groups;
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#
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# Using this approach allows us to further add criteria to the relation with
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# Rails thinking it's selecting data the usual way.
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#
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# If nested groups are not supported, ancestors_base is returned.
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# rubocop: disable CodeReuse/ActiveRecord
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def all_groups
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return ancestors_base unless Group.supports_nested_groups?
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ancestors = base_and_ancestors_cte
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descendants = base_and_descendants_cte
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ancestors_table = ancestors.alias_to(groups_table)
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descendants_table = descendants.alias_to(groups_table)
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relation = model
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.unscoped
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.with
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.recursive(ancestors.to_arel, descendants.to_arel)
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.from_union([
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model.unscoped.from(ancestors_table),
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model.unscoped.from(descendants_table)
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])
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read_only(relation)
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end
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# rubocop: enable CodeReuse/ActiveRecord
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private
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# rubocop: disable CodeReuse/ActiveRecord
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def base_and_ancestors_cte(stop_id = nil)
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cte = SQL::RecursiveCTE.new(:base_and_ancestors)
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cte << ancestors_base.except(:order)
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# Recursively get all the ancestors of the base set.
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parent_query = model
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.from([groups_table, cte.table])
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.where(groups_table[:id].eq(cte.table[:parent_id]))
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.except(:order)
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parent_query = parent_query.where(cte.table[:parent_id].not_eq(stop_id)) if stop_id
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cte << parent_query
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cte
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end
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# rubocop: enable CodeReuse/ActiveRecord
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# rubocop: disable CodeReuse/ActiveRecord
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def base_and_descendants_cte
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cte = SQL::RecursiveCTE.new(:base_and_descendants)
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cte << descendants_base.except(:order)
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# Recursively get all the descendants of the base set.
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cte << model
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.from([groups_table, cte.table])
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.where(groups_table[:parent_id].eq(cte.table[:id]))
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.except(:order)
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cte
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end
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# rubocop: enable CodeReuse/ActiveRecord
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def groups_table
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model.arel_table
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end
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def read_only(relation)
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# relations using a CTE are not safe to use with update_all as it will
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# throw away the CTE, hence we mark them as read-only.
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relation.extend(Gitlab::Database::ReadOnlyRelation)
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relation
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end
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end
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end
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