Optimizing a request

hi,
I have the following structure in my base 7.4.2

CREATE TABLE "public"."article" (
"art_id" INTEGER NOT NULL,
"rub_id" INTEGER DEFAULT '0' NOT NULL,
"art_titre" VARCHAR(100) DEFAULT '' NOT NULL,
"art_texte" TEXT NOT NULL,
"art_date" DATE NOT NULL,
"aut_id" INTEGER,
CONSTRAINT "article_pkey" PRIMARY KEY("art_id")
) WITH OIDS;

CREATE INDEX "article_art_date_index" ON "public"."article"
USING btree ("art_date");

CREATE INDEX "article_aut_id_index" ON "public"."article"
USING btree ("aut_id");

CREATE INDEX "article_rub_id_index" ON "public"."article"
USING btree ("rub_id");

CREATE INDEX "article_titre" ON "public"."article"
USING btree ("art_id", "art_titre");

CREATE TABLE "public"."auteur" (
"aut_id" INTEGER NOT NULL,
"aut_name" VARCHAR(100) DEFAULT '' NOT NULL,
CONSTRAINT "auteur_pkey" PRIMARY KEY("aut_id")
) WITH OIDS;

CREATE TABLE "public"."rubrique" (
"rub_id" INTEGER NOT NULL,
"rub_titre" VARCHAR(100) DEFAULT '' NOT NULL,
"rub_parent" INTEGER DEFAULT '0' NOT NULL,
"rub_date" DATE,
CONSTRAINT "rubrique_pkey" PRIMARY KEY("rub_id")
) WITH OIDS;

CREATE INDEX "rub_rub" ON "public"."rubrique"
USING btree ("rub_parent");

CREATE INDEX "rubrique_rub_date_index" ON "public"."rubrique"
USING btree ("rub_date");

CREATE INDEX "rubrique_rub_titre_index" ON "public"."rubrique"
USING btree ("rub_titre");

I want to optimize the following request and avoid the seq scan on the
table article (10000000 rows).

explain SELECT art_id, art_titre, art_texte, rub_titre
FROM article inner join rubrique on article.rub_id = rubrique.rub_id
where rub_parent = 8;

Hash Join (cost=8.27..265637.59 rows=25 width=130)
Hash Cond: ("outer".rub_id = "inner".rub_id)
-> Seq Scan on article (cost=0.00..215629.00 rows=10000000 width=108)
-> Hash (cost=8.26..8.26 rows=3 width=22)
-> Index Scan using rubrique_parent on rubrique
(cost=0.00..8.26 rows=3 width=22)
Index Cond: (rub_parent = 8)

thanks for your answers,

--
Jean-Max Reymond
CKR Solutions
http://www.ckr-solutions.com