Performance difference between char and int2 columns

["Yavuz Kavus" <yavuzkavus@xxxxxxxxx>]

hi everybody.

 

i have two table as :

 

CREATE TABLE "public"."tb_section_phones" (
  "section_id" INTEGER NOT NULL,
  "ptype_id" INTEGER NOT NULL,
  "country_code" SMALLINT DEFAULT 90,
  "domain_code" SMALLINT,
  "number" CHAR(7) NOT NULL,
  "extension" VARCHAR(6),
  CONSTRAINT "tb_section_phones_fk" FOREIGN KEY ("section_id")
    REFERENCES "public"."tb_sections"("sect_id")
    ON DELETE CASCADE
    ON UPDATE CASCADE
    NOT DEFERRABLE,
  CONSTRAINT "tb_section_phones_fk1" FOREIGN KEY ("ptype_id")
    REFERENCES "public"."tb_phone_types"("ptype_id")
    ON DELETE CASCADE
    ON UPDATE CASCADE
    NOT DEFERRABLE
) WITHOUT OIDS;

 

 

CREATE TABLE "public"."tb_section_phones_temp" (
  "sect_id" INTEGER NOT NULL,
  "ptype_id" INTEGER NOT NULL,
  "country_code" CHAR(2) DEFAULT 90,
  "domain_code" CHAR(3),
  "number" CHAR(7) NOT NULL,
  "extension" VARCHAR(6),
  CONSTRAINT "tb_section_phones_fk" FOREIGN KEY ("sect_id")
    REFERENCES "public"."tb_sections"("sect_id")
    ON DELETE CASCADE
    ON UPDATE CASCADE
    NOT DEFERRABLE,
  CONSTRAINT "tb_section_phones_fk2" FOREIGN KEY ("ptype_id")
    REFERENCES "public"."tb_phone_types"("ptype_id")
    ON DELETE CASCADE
    ON UPDATE CASCADE
    NOT DEFERRABLE
) WITHOUT OIDS;

 

the differences between two table are :

in the first table country_code type is smallint, in the second table char(2)

in the first table domain_code type is smallint, in the second table char(3)

.

 

The problem is that:

my both table has 10 records.

when i run this query on first table :

   select * from tb_section_phones;

   it lasts 0.02 sec.

when i run this query on second table :

   select * from tb_section_phones_temp;

   it lasts 0.13 sec.

 

6.5 times slower.

why so performance difference?

should i prefer int as column type?

 

thanks in advance.