Poor performing postgres sql - sql

Question

Here's my sql, followed by the explanation. I need to improve the performance. Any ideas?
PostgreSQL 9.3.12 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.8.4-2ubuntu1~14.04.1) 4.8.4, 64-bit
explain analyze
SELECT DISTINCT "apts"."id", practices.name AS alias_0
FROM "apts"
LEFT OUTER JOIN "patients" ON "patients"."id" = "apts"."patient_id"
LEFT OUTER JOIN "practices" ON "practices"."id" = "apts"."practice_id"
LEFT OUTER JOIN "eligibility_messages" ON "eligibility_messages"."apt_id" = "apts"."id"
WHERE (apts.eligibility_status_id != 1)
AND (eligibility_messages.current = 't')
AND (practices.id = '104')
ORDER BY practices.name desc
LIMIT 25 OFFSET 0
Limit (cost=881321.34..881321.41 rows=25 width=20) (actual time=2928.225..2928.227 rows=25 loops=1)
-> Sort (cost=881321.34..881391.94 rows=28240 width=20) (actual time=2928.223..2928.224 rows=25 loops=1)
Sort Key: practices.name
Sort Method: top-N heapsort Memory: 26kB
-> HashAggregate (cost=880242.03..880524.43 rows=28240 width=20) (actual time=2927.213..2927.319 rows=520 loops=1)
-> Nested Loop (cost=286614.55..880100.83 rows=28240 width=20) (actual time=206.180..2926.791 rows=520 loops=1)
-> Seq Scan on practices (cost=0.00..6.36 rows=1 width=20) (actual time=0.018..0.031 rows=1 loops=1)
Filter: (id = 104)
Rows Removed by Filter: 108
-> Hash Join (cost=286614.55..879812.07 rows=28240 width=8) (actual time=206.159..2926.643 rows=520 loops=1)
Hash Cond: (eligibility_messages.apt_id = apts.id)
-> Seq Scan on eligibility_messages (cost=0.00..561275.63 rows=2029532 width=4) (actual time=0.691..2766.867 rows=67559 loops=1)
Filter: current
Rows Removed by Filter: 3924633
-> Hash (cost=284614.02..284614.02 rows=115082 width=12) (actual time=121.957..121.957 rows=91660 loops=1)
Buckets: 16384 Batches: 2 Memory Usage: 1974kB
-> Bitmap Heap Scan on apts (cost=8296.88..284614.02 rows=115082 width=12) (actual time=19.927..91.038 rows=91660 loops=1)
Recheck Cond: (practice_id = 104)
Filter: (eligibility_status_id <> 1)
Rows Removed by Filter: 80169
-> Bitmap Index Scan on index_apts_on_practice_id (cost=0.00..8268.11 rows=177540 width=0) (actual time=16.856..16.856 rows=179506 loops=1)
Index Cond: (practice_id = 104)
Total runtime: 2928.361 ms

Answer 1

First, rewrite the query to a more manageable form:
SELECT DISTINCT a."id", pr.name AS alias_0
FROM "apts" a JOIN
"practices" pr
ON pr."id" = a."practice_id" JOIN
"eligibility_messages" em
ON em."apt_id" = a."id"
WHERE (a.eligibility_status_id <> 1) AND
(em.current = 't') AND
(a.practice_id = 104)
ORDER BY pr.name desc ;
Notes:
The WHERE clause turns the outer joins into inner joins anyway, so you might as well express them correctly.
I doubt pr.id is actually a string
The patients table isn't used, so I just removed it.
Perhaps you don't even need the select distinct any more.
Switched the condition in the where to apts rather than practices.
If this isn't fast enough, you want indexes, probably on apts(practice_id, eligibility_status_id, id), practices(id), and eligibility_messages(apt_id, current).