Re: Why index is not using here?

I am getting seq_scan on vtiger_account. Index is not using.

Could anyone please tell me what the reason is?

 

 

 explain   analyze                                                    
select *                                                      
from vtiger_account                                           
LEFT JOIN vtiger_account vtiger_account2                      
        ON vtiger_account.parentid = vtiger_account2.accountid 

                                                                     QUERY PLAN                                                                     
-----------------------------------------------------------------------------------------------------------------------------------------------------
 Hash Left Join  (cost=12506.65..38690.74 rows=231572 width=264) (actual time=776.910..4407.233 rows=231572 loops=1)
   Hash Cond: ("outer".parentid = "inner".accountid)
   ->  Seq Scan on vtiger_account  (cost=0.00..7404.72 rows=231572 width=132) (actual time=0.029..349.195 rows=231572 loops=1)
   ->  Hash  (cost=7404.72..7404.72 rows=231572 width=132) (actual time=776.267..776.267 rows=231572 loops=1)
         ->  Seq Scan on vtiger_account vtiger_account2  (cost=0.00..7404.72 rows=231572 width=132) (actual time=0.002..344.879 rows=231572 loops=1)
 Total runtime: 4640.868 ms
(6 rows)

vtigercrm504=# set enable_Seqscan = on;
SET

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Merge Left Join  (cost=0.00..1383629.28 rows=231572 width=264) (actual time=0.166..1924.417 rows=231572 loops=1)
   Merge Cond: ("outer".parentid = "inner".accountid)
   ->  Index Scan using vtiger_account_parentid_idx on vtiger_account  (cost=0.00..642475.34 rows=231572 width=132) (actual time=0.083..483.985 rows=231572 loops=1)
   ->  Index Scan using vtiger_account_pkey on vtiger_account vtiger_account2  (cost=0.00..737836.61 rows=231572 width=132) (actual time=0.074..532.463 rows=300971 loops=1)
 Total runtime: 2140.326 ms
(5 rows)

 

\d vtiger_account
                      Table "public.vtiger_account"
    Column     |          Type          |           Modifiers           
---------------+------------------------+--------------------------------
 accountid     | integer                | not null default 0
 accountname   | character varying(200) | not null
 parentid      | integer                | default 0
 account_type  | character varying(200) |
 industry      | character varying(200) |
 annualrevenue | integer                | default 0
 rating        | character varying(200) |
 ownership     | character varying(50)  |
 siccode       | character varying(50)  |
 tickersymbol  | character varying(30)  |
 phone         | character varying(30)  |
 otherphone    | character varying(30)  |
 email1        | character varying(100) |
 email2        | character varying(100) |
 website       | character varying(100) |
 fax           | character varying(30)  |
 employees     | integer                | default 0
 emailoptout   | character varying(3)   | default '0'::character varying
 notify_owner  | character varying(3)   | default '0'::character varying
Indexes:
    "vtiger_account_pkey" PRIMARY KEY, btree (accountid)
    "account_account_type_idx" btree (account_type)
    "vtiger_account_parentid_idx" btree (parentid)