# File lib/arel/engines/sql/compilers/postgresql_compiler.rb, line 38 38: def aliased_orders(orders) 39: # PostgreSQL does not allow arbitrary ordering when using DISTINCT ON, so we work around this 40: # by wrapping the +sql+ string as a sub-select and ordering in that query. 41: order = orders.join(', ').split(/,/).map { |s| s.strip }.reject(&:blank?) 42: order = order.zip((0...order.size).to_a).map { |s,i| "id_list.alias_#{i} #{'DESC' if s =~ /\bdesc$/i}" }.join(', ') 43: end
# File lib/arel/engines/sql/compilers/postgresql_compiler.rb, line 5 5: def select_sql 6: if !relation.orders.blank? && using_distinct_on? 7: selects = relation.select_clauses 8: joins = relation.joins(self) 9: wheres = relation.where_clauses 10: groups = relation.group_clauses 11: havings = relation.having_clauses 12: orders = relation.order_clauses 13: 14: subquery_clauses = [ "", 15: "SELECT #{selects.kind_of?(::Array) ? selects.join("") : selects.to_s}", 16: "FROM #{relation.from_clauses}", 17: joins, 18: ("WHERE #{wheres.join(' AND ')}" unless wheres.empty?), 19: ("GROUP BY #{groups.join(', ')}" unless groups.empty?), 20: ("HAVING #{havings.join(' AND ')}" unless havings.empty?) 21: ].compact.join ' ' 22: subquery_clauses << " #{locked}" unless locked.blank? 23: 24: build_query "SELECT * FROM (#{build_query subquery_clauses}) AS id_list", 25: "ORDER BY #{aliased_orders(orders)}", 26: ("LIMIT #{relation.taken}" unless relation.taken.blank? ), 27: ("OFFSET #{relation.skipped}" unless relation.skipped.blank? ) 28: else 29: super 30: end 31: end
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