DB slow down after table partition

I already sent the mail earlier. but added wrong explain. So I mail it
again.

I have more than 1300000 records in crm table and I partioned the table with
deleted = 0 key.
It is working fine except that after partioion query is taking more time
than the previous one.
I already set constraint_exclusion = on;

I added the explain anayze for both the states.
Any idea please why the delay is being occured.

explain analyze
select *
from crm as c
inner join activity as a on c.crmid = a.activityid
inner join seactivityrel as s on c.crmid= s.crmid
where c.deleted = 0;

Before partiion:

QUERY PLAN
--------------------------------------------------------------------
Merge Join (cost=0.00..107563.24 rows=308029 width=459) (actual
time=13912.064..18196.713 rows=1 loops=1)
Merge Cond: ("outer".crmid = "inner".crmid)
-> Merge Join (cost=0.00..60995.18 rows=239062 width=451) (actual
time=60.972..9698.700 rows=331563 loops=1)
Merge Cond: ("outer".crmid = "inner".activityid)
-> Index Scan using crm_pkey on crm c (cost=0.00..43559.49 rows=945968
width=308) (actual time=52.877..6139.369 rows=949938 loops=1)
Filter: (deleted = 0)
-> Index Scan using activity_pkey on activity a (cost=0.00..11822.64
rows=343003 width=143) (actual time=7.999..1456.232 rows=343001 loops=1)
-> Index Scan using seactivityrel_crmid_idx on seactivityrel s
(cost=0.00..38518.04 rows=1748826 width=8) (actual time=0.305..6278.171
rows=1748826 loops=1)
Total runtime: 18196.832 ms

After partition:

QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Hash Join (cost=115857.19..357283.03 rows=8306416340 width=548) (actual
time=85871.145..85874.584 rows=1 loops=1)
Hash Cond: ("outer".crmid = "inner".activityid)
-> Append (cost=0.00..37825.51 rows=949942 width=329) (actual
time=0.167..72430.097 rows=949941 loops=1)
-> Seq Scan on crm c (cost=0.00..13.25 rows=1 width=280) (actual
time=0.001..0.001 rows=0 loops=1)
Filter: (deleted = 0)
-> Seq Scan on crm_active c (cost=0.00..37812.26 rows=949941 width=329)
(actual time=0.162..70604.116 rows=949941 loops=1)
Filter: (deleted = 0)
-> Hash (cost=73058.13..73058.13 rows=1748826 width=152) (actual
time=9603.453..9603.453 rows=1 loops=1)
-> Merge Join (cost=0.00..73058.13 rows=1748826 width=152) (actual
time=7959.707..9603.101 rows=1 loops=1)
Merge Cond: ("outer".activityid = "inner".crmid)
-> Index Scan using activity_pkey on activity a (cost=0.00..11822.25
rows=343004 width=144) (actual time=88.467..1167.556 rows=343001 loops=1)
-> Index Scan using seactivityrel_crmid_idx on seactivityrel s
(cost=0.00..38518.04 rows=1748826 width=8) (actual time=0.459..6148.843
rows=1748826 loops=1)
Total runtime: 85875.591 ms
(13 rows)