path: root/activerecord/lib/arel/visitors/oracle12.rb

# frozen_string_literal: true

module Arel # :nodoc: all
  module Visitors
    class Oracle12 < Arel::Visitors::ToSql
      private
        def visit_Arel_Nodes_SelectStatement(o, collector)
          # Oracle does not allow LIMIT clause with select for update
          if o.limit && o.lock
            raise ArgumentError, <<~MSG
              Combination of limit and lock is not supported. Because generated SQL statements
              `SELECT FOR UPDATE and FETCH FIRST n ROWS` generates ORA-02014.
            MSG
          end
          super
        end

        def visit_Arel_Nodes_SelectOptions(o, collector)
          collector = maybe_visit o.offset, collector
          collector = maybe_visit o.limit, collector
          maybe_visit o.lock, collector
        end

        def visit_Arel_Nodes_Limit(o, collector)
          collector << "FETCH FIRST "
          collector = visit o.expr, collector
          collector << " ROWS ONLY"
        end

        def visit_Arel_Nodes_Offset(o, collector)
          collector << "OFFSET "
          visit o.expr, collector
          collector << " ROWS"
        end

        def visit_Arel_Nodes_Except(o, collector)
          collector << "( "
          collector = infix_value o, collector, " MINUS "
          collector << " )"
        end

        def visit_Arel_Nodes_UpdateStatement(o, collector)
          # Oracle does not allow ORDER BY/LIMIT in UPDATEs.
          if o.orders.any? && o.limit.nil?
            # However, there is no harm in silently eating the ORDER BY clause if no LIMIT has been provided,
            # otherwise let the user deal with the error
            o = o.dup
            o.orders = []
          end

          super
        end

        def visit_Arel_Nodes_BindParam(o, collector)
          collector.add_bind(o.value) { |i| ":a#{i}" }
        end

        def is_distinct_from(o, collector)
          collector << "DECODE("
          collector = visit [o.left, o.right, 0, 1], collector
          collector << ")"
        end
    end
  end
end