select on index column,why PG still use seq scan?

[Xiaoyulei <xiaoyulei@xxxxxxxxxx>]

I create a table and insert some items.

I create index on every column.

And I execute select, I thought it should use index scan, but it is still seq scan. Why PG do not use index scan?

 

create table v_org_info(

org_no varchar2(8), org_nm varchar2(80),

org_no_l1 varchar2(8), org_nm_l1 varchar2(80),

org_no_l2 varchar2(8), org_nm_l2 varchar2(80)

);

 

create index idx_v_org_info_org_no on v_org_info(org_no);

create index idx_v_org_info_org_no_l1 on v_org_info(org_no_l1);

create index idx_v_org_info_org_no_l2 on v_org_info(org_no_l2);

 

begin

  for i in 1..20000 loop

    insert into v_org_info values(i,'test',i,'test',i,'test');

    insert into adm_org_info values(i);

  end loop;

end;

 

 

POSTGRES=# explain analyze select a.org_nm  from v_org_info a where a.org_no = 1000;

                                                        QUERY PLAN                                                        

---------------------------------------------------------------------------------------------------------------------------

Seq Scan on V_ORG_INFO A  (cost=0.00..189.97 rows=9 width=178, batch_size=100) (actual time=0.930..18.034 rows=1 loops=1)

   Filter: (INT4IN(VARCHAROUT(ORG_NO)) = 1000)

   Rows Removed by Filter: 19999

Total runtime: 18.099 ms

(4 rows)