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Diffstat (limited to 'activerecord/lib/arel/visitors/mssql.rb')
-rw-r--r-- | activerecord/lib/arel/visitors/mssql.rb | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/activerecord/lib/arel/visitors/mssql.rb b/activerecord/lib/arel/visitors/mssql.rb new file mode 100644 index 0000000000..9aedc51d15 --- /dev/null +++ b/activerecord/lib/arel/visitors/mssql.rb @@ -0,0 +1,125 @@ +# frozen_string_literal: true + +module Arel # :nodoc: all + module Visitors + class MSSQL < Arel::Visitors::ToSql + RowNumber = Struct.new :children + + def initialize(*) + @primary_keys = {} + super + end + + 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 visit_Arel_Nodes_DeleteStatement(o, collector) + collector << "DELETE " + if o.limit + collector << "TOP (" + visit o.limit.expr, collector + collector << ") " + end + collector << "FROM " + collector = visit o.relation, collector + if o.wheres.any? + collector << " WHERE " + inject_join o.wheres, collector, AND + else + collector + 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? + def find_left_table_pk(o) + if o.kind_of?(Arel::Nodes::Join) + find_left_table_pk(o.left) + elsif o.instance_of?(Arel::Table) + find_primary_key(o) + end + end + + def find_primary_key(o) + @primary_keys[o.name] ||= begin + primary_key_name = @connection.primary_key(o.name) + # some tables might be without primary key + primary_key_name && o[primary_key_name] + end + end + end + end +end |