Hello all, When dealing with legacy schemas or data models where the Active Record pattern is a bit of a stretch complex joins are often necessary. Many joins can be eliminated by using set operations on multiple queries. Arel already supports set operations, and the Set module from the standard library already provide useful semantics.
Would this be something that could be of general use? I've created a gem that patches these operations into ActiveRecord::Relation (https://github.com/delonnewman/activerecord-setops), and tested it with Rails 5. It's very little code: module ActiveRecord class Relation # Performs a set theoretic union works like `Array#+` but puts the load on the database # and allows you to chain more relation operations. def union(other) binary_operation(Arel::Nodes::Union, other) end alias | union alias + union def union_all(other) binary_operation(Arel::Nodes::UnionAll, other) end def intersect(other) binary_operation(Arel::Nodes::Intersect, other) end alias & intersect def except(other) binary_operation(Arel::Nodes::Except, other) end alias difference except alias - except private def binary_operation(op_class, other) @klass.unscoped.from(Arel::Nodes::TableAlias.new(op_class.new(self. arel.ast, other.arel.ast), @klass.arel_table.name)) end end end Thanks, Delon Newman -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Core" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/rubyonrails-core/e9721df1-09cd-4733-bfa2-33728189ea21%40googlegroups.com.
