CREATE TABLE wobj ( -- Универсальный объект, для хранения ID
   id bigserial NOT NULL,
   CONSTRAINT pk_wobj PRIMARY KEY (id)
);

CREATE TABLE posts ( -- Комментарии
-- Inherited:   id bigint NOT NULL DEFAULT nextval('wobj_id_seq'::regclass),
   post_id bigint,
   dpost timestamp without time zone DEFAULT now(),
   body xml,
   CONSTRAINT posts_pk_id PRIMARY KEY (id)
) INHERITS (wobj);

CREATE TABLE news ( -- Собственно новости
-- Inherited:   id bigint NOT NULL DEFAULT nextval('wobj_id_seq'::regclass),
-- Inherited:   post_id bigint,
-- Inherited:   dpost timestamp without time zone DEFAULT now(),
-- Inherited:   body xml,
   title character varying( 132 ),
   brief character varying( 255 ),
   CONSTRAINT news_pk_id PRIMARY KEY (id)
) INHERITS (posts);

CREATE TABLE tags ( -- Ярлыки
  id bigserial NOT NULL,
  tag character varying( 64 ),
  CONSTRAINT tags_pk_id PRIMARY KEY (id)
);

CREATE TABLE tag_post ( -- Связка ярлыки  m-to-m новости
   tag_id bigint NOT NULL,
   post_id bigint NOT NULL,
   CONSTRAINT pk_tag_post PRIMARY KEY (tag_id, post_id),
   CONSTRAINT tag_post_fk_news_id FOREIGN KEY (post_id)
      REFERENCES news (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION, -- Ссылка на ID ноаости
   CONSTRAINT tag_post_fk_tags_id FOREIGN KEY (tag_id)
      REFERENCES tags (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION -- Ссылка на ID ярлыка
);