module Arel module Visitors class MSSQL < Arel::Visitors::ToSql RowNumber = Struct.new :children private # `top` wouldn't really work here. I.e. User.select("distinct first_name").limit(10) would generate # "select top 10 distinct first_name from users", which is invalid query! it should be # "select distinct top 10 first_name from users" def visit_Arel_Nodes_Top o "" end def visit_Arel_Visitors_MSSQL_RowNumber o, collector collector << "ROW_NUMBER() OVER (ORDER BY " inject_join(o.children, collector, ', ') << ") as _row_num" end def visit_Arel_Nodes_SelectStatement o, collector if !o.limit && !o.offset return super end is_select_count = false o.cores.each { |x| core_order_by = row_num_literal determine_order_by(o.orders, x) if select_count? x x.projections = [core_order_by] is_select_count = true else x.projections << core_order_by end } if is_select_count # fixme count distinct wouldn't work with limit or offset collector << "SELECT COUNT(1) as count_id FROM (" end collector << "SELECT _t.* FROM (" collector = o.cores.inject(collector) { |c,x| visit_Arel_Nodes_SelectCore x, c } collector << ") as _t WHERE #{get_offset_limit_clause(o)}" if is_select_count collector << ") AS subquery" else collector end end def get_offset_limit_clause o first_row = o.offset ? o.offset.expr.to_i + 1 : 1 last_row = o.limit ? o.limit.expr.to_i - 1 + first_row : nil if last_row " _row_num BETWEEN #{first_row} AND #{last_row}" else " _row_num >= #{first_row}" end end def determine_order_by orders, x if orders.any? orders elsif x.groups.any? x.groups else pk = find_left_table_pk(x.froms) pk ? [pk] : [] end end def row_num_literal order_by RowNumber.new order_by end def select_count? x x.projections.length == 1 && Arel::Nodes::Count === x.projections.first end # FIXME raise exception of there is no pk? # FIXME!! Table.primary_key will be deprecated. What is the replacement?? def find_left_table_pk o return o.primary_key if o.instance_of? Arel::Table find_left_table_pk o.left if o.kind_of? Arel::Nodes::Join end end end end