Problemas para desarrollar una funcion

[Osay]

esta es mi tabla tipocomponente

CREATE TABLE "public"."tipocomponente" (
"ComponenteCod" CHAR(12) DEFAULT ''::bpchar NOT NULL,
"ComponenteDscrip" VARCHAR(50) DEFAULT ''::character varying NOT NULL,
"Maximo_horas_uso" BIGINT,
"Precio" NUMERIC,
"FabricanteCod" CHAR(10) DEFAULT ''::bpchar NOT NULL,
CONSTRAINT "tipocomponente_pkey" PRIMARY KEY("ComponenteCod"),
CONSTRAINT "tipocomponente_fk" FOREIGN KEY ("FabricanteCod")
REFERENCES "public"."fabricante"("FabricanteCod")
ON DELETE NO ACTION
ON UPDATE NO ACTION
NOT DEFERRABLE
) WITHOUT OIDS;