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ここに私のSQLとその説明が続きます。パフォーマンスを改善する必要があります。何か案は?パフォーマンスが悪いpostgres sql
のgccでコンパイルx86_64版 - 未知のlinux-gnuの、上のPostgreSQL 9.3.12(Ubuntuの4.8.4-2ubuntu1〜14.04.1)4.8.4、64ビット
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
検索しているすべての結合値とフィールドにインデックスがありますか?さらに、Eligibility_messagesとPracticesの左外部結合は無効になり、それらを移動して内部結合にすることができます。 practices.nameにインデックスがありますか? – xQbert