CREATE TABLE picture_categories( pcid int4 NOT NULL DEFAULT nextval('picture_categories_pcid_seq'::regclass), pid int4 NOT NULL, cat_id int4, CONSTRAINT picture_categories_pkey PRIMARY KEY (pcid), CONSTRAINT picture_categories_pid_key UNIQUE (pid, cat_id)) WITHOUT OIDS;CREATE INDEX idx_picture_categories_cat_id ON picture_categories USING btree (cat_id);CREATE INDEX idx_picture_categories_pid ON picture_categories USING btree (pid);CREATE INDEX idx_picture_categories_pid_and_cat_id ON picture_categories USING btree (pid, cat_id);-----------------------------------1. Drop pcid and use idx_picture_categories_pid_and_cat_id as PK2. Change cat_id to int2 if possible