partitioned_gifts.sql

create table gifts_partitioned (
  id integer not null default nextval('gifts_id_seq'::regclass),
  ; ...
  finished boolean not null default false,
  ; ...

  PRIMARY KEY(id, finished)
)
partition by list(finished);

create table gifts_unfinished
partition of gifts_partitioned for values in (false);

create table gifts_finished
partition of gifts_partitioned for values in (true);

trigger.ruby

CREATE OR REPLACE FUNCTION create_or_update_gifts_in_partitioned_table()
      RETURNS TRIGGER
      AS
      $$
      BEGIN
        if exists (select 1 from gifts_partitioned where id = NEW.id) then
          update gifts_partitioned set#{' '}
          #{
            (Gift.columns.map(&:name) - %w[id]).map do |column|
              "#{column} = NEW.#{column}"
            end.join(", ")
          }
          where id = NEW.id;
        else
          insert into gifts_partitioned (#{Gift.columns.map(&:name).join(",")})
          values (
            #{
              Gift.columns.map(&:name).map do |column|
                "NEW.#{column}"
              end.join(", ")
            }
          );
        end if;

        return null;
      END;
      $$
      LANGUAGE plpgsql;

      create TRIGGER copy_to_partitioned_table after INSERT or UPDATE on gifts
      for each row EXECUTE PROCEDURE create_or_update_gifts_in_partitioned_table();