112 lines
3.4 KiB
Ruby
112 lines
3.4 KiB
Ruby
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 a relation that includes the ancestors_base set of groups
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# and all their ancestors (recursively).
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def base_and_ancestors
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return ancestors_base unless Group.supports_nested_groups?
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base_and_ancestors_cte.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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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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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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union = SQL::Union.new([model.unscoped.from(ancestors_table),
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model.unscoped.from(descendants_table)])
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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.to_sql}) #{model.table_name}")
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end
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private
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def base_and_ancestors_cte
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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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cte << 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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cte
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end
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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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def groups_table
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model.arel_table
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end
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end
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end
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