ืืขืืื Postgres, ืืื ืืงืกืื ืืืื ืืื ืื ืืืื ืืขืื ืืืืกืื ืฉื ืืกื ื ืชืื ืื (ืืืืื ื "ืขืจืืื"). Postgres ืื ืชืืื ืืืฉืืืืืช ืขืืืจื, ืืืจืืืืงืืืจืช MVCC ืืืจืืช ืื ืืงืื ืืจืกืืืช ืจืืืช ืฉื ืืืชื tuple. ืืื, ืืฉืื ืืืื ืืืืืช ืืกืืื ืืืฆืืจ ืืืชืืืง ืืื ืืงืกืื ืืขืืืื ืืชืืืื ืืืคืืืงืฆืืืช.
ืืืื ืืกืคืจ ืืืคืื ืืืืขืื ืืฉืืคืืจ ืืฉืืืืฉ ืืืื ืืงืกืื.
ืืขืจื: ืืฉืืืืชืืช ืืืืฆืืืช ืืืื ืคืืขืืืช ืขื ืงืืืฅ ืืื ืฉืื ืื
ืฉืืืืฉ ืืืื ืืงืกืื ืืืกืื
ืืื ื ืืื ืืงืฉื ืืืืืืฅ ืืชืืืืช ืืื"ื ืขืืืจ ืืฉืชืืฉืื ืื ืคืขืืืื. ืฉืืืื customer
ืืฉ ืขืืืื active
, ืืืฉืืืืชื ืคืฉืืื:
pagila=# EXPLAIN SELECT email FROM customer WHERE active=0;
QUERY PLAN
-----------------------------------------------------------
Seq Scan on customer (cost=0.00..16.49 rows=15 width=32)
Filter: (active = 0)
(2 rows)
ืืฉืืืืชื ืืคืขืืื ืืช ืจืฆืฃ ืกืจืืงืช ืืืืื ืืืื customer
. ืืืื ื ืืฆืืจ ืืื ืืงืก ืขื ืขืืืื active
:
pagila=# CREATE INDEX idx_cust1 ON customer(active);
CREATE INDEX
pagila=# EXPLAIN SELECT email FROM customer WHERE active=0;
QUERY PLAN
-----------------------------------------------------------------------------
Index Scan using idx_cust1 on customer (cost=0.28..12.29 rows=15 width=32)
Index Cond: (active = 0)
(2 rows)
ืื ืขืืจ, ืืกืจืืงื ืฉืืืืจ ืืื ืืคืื ื"index scan
". ืื ืืืืจ ืฉืคืืกืืืจืก ืืกืจืืง ืืช ืืืื ืืงืก "idx_cust1
", ืืืืืจ ืืื ืืืฉื ืืืคืฉ ืืขืจืืืช ืืืืื ืืื ืืงืจืื ืืช ืืขืจืืื ืฉื ืขืืืืืช ืืืจืืช (ืืืงืจื ืื, ืืขืืืื email
) ืฉืืฉืืืืชื ืฆืจืืื.
ืืื ืืงืกืื ืืืกืื ืืืฆืืื ื-PostgreSQL 11. ืื ืืืคืฉืจืื ืื ืืืืื ืขืืืื ื ืืกืคืช ืืืช ืื ืืืชืจ ืืืื ืืงืก ืขืฆืื - ืืขืจืืื ืฉืืื ืืืืืกื ืื ืืืืืจ ื ืชืื ื ืืืื ืืงืก.
ืื ื ืืฆืื ื ืืช ืืชืืื ื ืืื ืืืืกืคื ื ืืช ืขืจื ืืืืืืื ืืชืื ืืืื ืืงืก, ืื Postgres ืื ืืื ืฆืจืื ืืืคืฉ ืืช ืืขืจื ืืขืจืืืช ืืืืื. email
. ืืื ื ืจืื ืื โโืื ืืขืืื:
pagila=# CREATE INDEX idx_cust2 ON customer(active) INCLUDE (email);
CREATE INDEX
pagila=# EXPLAIN SELECT email FROM customer WHERE active=0;
QUERY PLAN
----------------------------------------------------------------------------------
Index Only Scan using idx_cust2 on customer (cost=0.28..12.29 rows=15 width=32)
Index Cond: (active = 0)
(2 rows)
ยซIndex Only Scan
' ืืืืจ ืื ื ืฉืืฉืืืืชื ืืงืืงื ืืขืช ืจืง ืืืื ืืงืก, ืื ืฉืขืืืจ ืืืืื ืข ืืื ืงืื/ืคืื ืืืกืง ืืื ืืงืจืื ืืช ืขืจืืืช ืืืืื.
ืืื ืืงืกืื ืืืกืื ืืืื ืื ืืจืืข ืจืง ืขืืืจ ืขืฆื B. ืขื ืืืช, ืืืงืจื ืื, ืืืืฅ ืืชืืืืงื ืืืื ืืืื ืืืชืจ.
ืฉืืืืฉ ืืืื ืืงืกืื ืืืงืืื
ืืื ืืงืก ืืืงื ืืืกืืฃ ืจืง ืชืช-ืงืืืฆื ืฉื ืืฉืืจืืช ืืืืื. ืื ืืืกื ืืช ืืืื ืืืื ืืงืกืื ืืืืคื ืืช ืืกืจืืงื ืืืืืจ ืืืชืจ.
ื ื ืื ืฉืื ื ืจืืฆืื ืืงืื ืจืฉืืื ืฉื ืืชืืืืช ืืืืืืื ืฉื ืืืงืืืืช ืฉืื ื ืืงืืืคืืจื ืื. ืืืงืฉื ืชืืื ืื:
SELECT c.email FROM customer c
JOIN address a ON c.address_id = a.address_id
WHERE a.district = 'California';
which has a query plan that involves scanning both the tables that are joined:
pagila=# EXPLAIN SELECT c.email FROM customer c
pagila-# JOIN address a ON c.address_id = a.address_id
pagila-# WHERE a.district = 'California';
QUERY PLAN
----------------------------------------------------------------------
Hash Join (cost=15.65..32.22 rows=9 width=32)
Hash Cond: (c.address_id = a.address_id)
-> Seq Scan on customer c (cost=0.00..14.99 rows=599 width=34)
-> Hash (cost=15.54..15.54 rows=9 width=4)
-> Seq Scan on address a (cost=0.00..15.54 rows=9 width=4)
Filter: (district = 'California'::text)
(6 rows)
ืื ืืชื ื ืื ื ืืื ืืงืกืื ืจืืืืื:
pagila=# CREATE INDEX idx_address1 ON address(district);
CREATE INDEX
pagila=# EXPLAIN SELECT c.email FROM customer c
pagila-# JOIN address a ON c.address_id = a.address_id
pagila-# WHERE a.district = 'California';
QUERY PLAN
---------------------------------------------------------------------------------------
Hash Join (cost=12.98..29.55 rows=9 width=32)
Hash Cond: (c.address_id = a.address_id)
-> Seq Scan on customer c (cost=0.00..14.99 rows=599 width=34)
-> Hash (cost=12.87..12.87 rows=9 width=4)
-> Bitmap Heap Scan on address a (cost=4.34..12.87 rows=9 width=4)
Recheck Cond: (district = 'California'::text)
-> Bitmap Index Scan on idx_address1 (cost=0.00..4.34 rows=9 width=0)
Index Cond: (district = 'California'::text)
(8 rows)
ืกืจืืง address
ืืืืืฃ ืืกืจืืงืช ืืื ืืงืก idx_address1
ืืื ืกืจืง ืืช ืืขืจืืื address
.
ืืืืืื ืฉืืืืืจ ืืฉืืืืชื ืชืืืคื ืืฆืจืื ืืืฆืข ืืืคืืืืืืฆืื, ื ืืื ืืืฉืชืืฉ ืืืื ืืงืก ืืืงื, ืฉืืื ืืงืก ืจืง ืืช ืืฉืืจืืช ืขื ืืืชืืืืช ืฉืืื ืืืืื โCaliforniaโ
:
pagila=# CREATE INDEX idx_address2 ON address(address_id) WHERE district='California';
CREATE INDEX
pagila=# EXPLAIN SELECT c.email FROM customer c
pagila-# JOIN address a ON c.address_id = a.address_id
pagila-# WHERE a.district = 'California';
QUERY PLAN
------------------------------------------------------------------------------------------------
Hash Join (cost=12.38..28.96 rows=9 width=32)
Hash Cond: (c.address_id = a.address_id)
-> Seq Scan on customer c (cost=0.00..14.99 rows=599 width=34)
-> Hash (cost=12.27..12.27 rows=9 width=4)
-> Index Only Scan using idx_address2 on address a (cost=0.14..12.27 rows=9 width=4)
(5 rows)
ืืขืช ืืฉืืืืชื ืจืง ืงืืจืืช idx_address2
ืืืื ื ื ืืืข ืืฉืืืื address
.
ืฉืืืืฉ ืืืื ืืงืกืื ืืจืืื ืขืจืืื
ืืืชืื ืฉืืืง ืืืขืืืืืช ืืืืกืคืช ืืื ืืงืก ืืื ื ืืืืืืช ืกืื ื ืชืื ืื ืกืงืืืจื. ืกืืื ืขืืืืืช ืืื jsonb
, arrays
ะธ tsvector
ืืืืืื ืขืจืืื ืืืจืืืื ืื ืืจืืืื. ืื ืืชื ืฆืจืื ืืืื ืืงืก ืขืืืืืช ืืืื, ืืชื ืืืจื ืืื ืฆืจืื ืืืคืฉ ืืื ืืขืจืืื ืืืืืืื ืืืืชื ืขืืืืืช.
ืืืื ื ื ืกื ืืืฆืื ืืช ืืืืชืจืืช ืฉื ืื ืืกืจืืื ืืืืืืื ืืืจืืช ืืฆืืืืืื ืื ืืืฆืืืื. ืฉืืืื film
ืืฉ ืขืืืืช ืืงืกื ืฉื ืงืจืืช special_features
. ืื ืืกืจื ืืฉ "ืืืคืืื ืืืืื", ืื ืืขืืืื ืืืืื ืืช ืืืืื ื ืืืขืจื ืืงืกื Behind The Scenes
. ืืื ืืืคืฉ ืืช ืื ืืกืจืืื ืืืื, ืื ืื ื ืฆืจืืืื ืืืืืจ ืืช ืื ืืฉืืจืืช ืขื "ืืืืืจื ืืงืืขืื" ืืชื ืื ืขืจืื ืืขืจื special_features
:
SELECT title FROM film WHERE special_features @> '{"Behind The Scenes"}';
ืืคืขืื ืงืื ืื @>
ืืืืง ืื ืืฆื ืืืื ื ืืื ืชืช-ืงืืืฆื ืฉื ืืฆื ืืฉืืืื.
ืืงืฉืช ืชืืื ืืช:
pagila=# EXPLAIN SELECT title FROM film
pagila-# WHERE special_features @> '{"Behind The Scenes"}';
QUERY PLAN
-----------------------------------------------------------------
Seq Scan on film (cost=0.00..67.50 rows=5 width=15)
Filter: (special_features @> '{"Behind The Scenes"}'::text[])
(2 rows)
ืื ืฉืืืงืฉ ืกืจืืงืช ืขืจืืื ืืืื ืืขืืืช ืฉื 67.
ืืื ื ืจืื ืื โโืืื ืืงืก ืขืฅ B ืจืืื ืขืืืจ ืื ื:
pagila=# CREATE INDEX idx_film1 ON film(special_features);
CREATE INDEX
pagila=# EXPLAIN SELECT title FROM film
pagila-# WHERE special_features @> '{"Behind The Scenes"}';
QUERY PLAN
-----------------------------------------------------------------
Seq Scan on film (cost=0.00..67.50 rows=5 width=15)
Filter: (special_features @> '{"Behind The Scenes"}'::text[])
(2 rows)
ืืืื ืืคืืื ืื ื ืืฉื. ืืื ืืงืก ืขืฅ B ืืื ื ืืืืข ืืงืืืื ืฉื ืืืื ืืื ืืืืืื ืืขืจืืื ืืืฆืืจืคืื.
ืื ืื ื ืฆืจืืืื ืืื GIN.
pagila=# CREATE INDEX idx_film2 ON film USING GIN(special_features);
CREATE INDEX
pagila=# EXPLAIN SELECT title FROM film
pagila-# WHERE special_features @> '{"Behind The Scenes"}';
QUERY PLAN
---------------------------------------------------------------------------
Bitmap Heap Scan on film (cost=8.04..23.58 rows=5 width=15)
Recheck Cond: (special_features @> '{"Behind The Scenes"}'::text[])
-> Bitmap Index Scan on idx_film2 (cost=0.00..8.04 rows=5 width=0)
Index Cond: (special_features @> '{"Behind The Scenes"}'::text[])
(4 rows)
ืืื ืืงืก GIN ืชืืื ืืืืคืื ืขืจืืื ืืืืืื ืืื ืขืจืืื ืืจืืืืื ืฉืฆืืจืคื ืืืื ืืงืก, ืืืชืืฆืื ืืื ืขืืืช ืชืืื ืืช ืฉืืืืชืืช ืืื ืืืชืจ ืืืฆืืืช.
ืืืคืืจืืช ืืืื ืืงืกืื ืืคืืืื
ืืื ืืงืกืื ืืฆืืืจืื ืขื ืืืื, ืืืคืขืืื ืืื ืืงืก ืืืฉ ืขืฉืื ืืืืื ืืืืจื ืืื ืืืื ืืืงืืืืื. ืืชื ืืืื ืืืฉืชืืฉ ืืชืฆืืืช ืืงืืืื ืืื ืืงืื ืืืืจืืช SQL ืื ืืชื ืืช ืืงืจืืื ืขื ืืื ืืื ืฉื ืืื ืืงืกืื. pg_indexes
. ืืชื ืืืื ืื ืืืฆืื ืืงืืืช ืืืืจืืช ืืืืช:
SELECT array_agg(indexname) AS indexes, replace(indexdef, indexname, '') AS defn
FROM pg_indexes
GROUP BY defn
HAVING count(*) > 1;
And hereโs the result when run on the stock pagila database:
pagila=# SELECT array_agg(indexname) AS indexes, replace(indexdef, indexname, '') AS defn
pagila-# FROM pg_indexes
pagila-# GROUP BY defn
pagila-# HAVING count(*) > 1;
indexes | defn
------------------------------------------------------------------------+------------------------------------------------------------------
{payment_p2017_01_customer_id_idx,idx_fk_payment_p2017_01_customer_id} | CREATE INDEX ON public.payment_p2017_01 USING btree (customer_id
{payment_p2017_02_customer_id_idx,idx_fk_payment_p2017_02_customer_id} | CREATE INDEX ON public.payment_p2017_02 USING btree (customer_id
{payment_p2017_03_customer_id_idx,idx_fk_payment_p2017_03_customer_id} | CREATE INDEX ON public.payment_p2017_03 USING btree (customer_id
{idx_fk_payment_p2017_04_customer_id,payment_p2017_04_customer_id_idx} | CREATE INDEX ON public.payment_p2017_04 USING btree (customer_id
{payment_p2017_05_customer_id_idx,idx_fk_payment_p2017_05_customer_id} | CREATE INDEX ON public.payment_p2017_05 USING btree (customer_id
{idx_fk_payment_p2017_06_customer_id,payment_p2017_06_customer_id_idx} | CREATE INDEX ON public.payment_p2017_06 USING btree (customer_id
(6 rows)
ืืื ืืงืกืื ืฉื Superset
ืืืื ืืงืจืืช ืฉืืกืืคื ืฉื ืืืจ ืชืืืขื ืขื ืืื ืืงืกืื ืจืืื, ืฉืืื ืืื ืืื ืืงืก ืงืืืฆื ืฉื ืขืืืืืช ืฉืืื ืืงืกืืช ืืื ืืงืกืื ืืืจืื. ืื ืขืฉืื ืืืืืช ืจืฆืื ืืืืื ืื - ืขืจืืช ืืขื ืขืฉืืื ืืืจืื ืืกืจืืงืืช ืืื ืืงืก ืืืื, ืืื ืืื, ืืื ืืื ืขืฉืืื ืืชืคืืก ืืืชืจ ืืื ืืงืื, ืื ืฉืืฉืืืืชื ืฉืืขืจืืช ืืขื ื ืืขืื ืืืืขื ืืื ื ืืฉืืืืฉ ืขืื.
ืื ืืชื ืฆืจืื ืืืคืื ืืช ืืืืืจื ืฉื ืืื ืืงืกืื ืืืื ืืืืืืืื, ืืชื ืืืื ืืืชืืื ืขื pg_catalog
.
ืืื ืืงืกืื ืฉืืื ื ืืฉืืืืฉ
ืืื ืฉืืืฉืืืื ืืืฉืชืืฉืื ืืืกืื ื ืชืื ืื ืืชืคืชืืื, ืื ืื ืืฉืืืืชืืช ืฉืืื ืื ืืฉืชืืฉืื ืืชืคืชืืืช. ืื ื ืืชื ืขืื ืืืฉืชืืฉ ืืืื ืืงืกืื ืฉื ืืกืคื ืงืืื ืืื ืขื ืืื ืฉืืืืชื ืืืฉืื. ืืื ืคืขื ืฉืืื ืืงืก ื ืกืจืง, ืืื ืืกืืื ืขื ืืื ืื ืื ืืกืืืืกืืืงื, ืืืชืฆืืืช ืงืืืื ืืืขืจืืช pg_stat_user_indexes
ืืชื ืืืื ืืจืืืช ืืช ืืขืจื idx_scan
, ืฉืืื ืืื ื ืืฆืืืจ. ืืขืงื ืืืจ ืขืจื ืื ืขื ืคื ื ืชืงืืคื ืฉื ืืื (ื ื ืื ืืืืฉ) ืืืชื ืืืฉื ืืื ืืืืื ืืื ืืงืกืื ืืื ื ืืฉืืืืฉ ืืืืืืื ืืืืฉืื.
ืื ื ืฉืืืืชื ืืงืื ืืช ืกืคืืจืช ืืกืจืืงื ืื ืืืืืช ืฉื ืื ืืืื ืืงืกืื ืืกืืืื โpublicโ
:
SELECT relname, indexrelname, idx_scan
FROM pg_catalog.pg_stat_user_indexes
WHERE schemaname = 'public';
with output like this:
pagila=# SELECT relname, indexrelname, idx_scan
pagila-# FROM pg_catalog.pg_stat_user_indexes
pagila-# WHERE schemaname = 'public'
pagila-# LIMIT 10;
relname | indexrelname | idx_scan
---------------+--------------------+----------
customer | customer_pkey | 32093
actor | actor_pkey | 5462
address | address_pkey | 660
category | category_pkey | 1000
city | city_pkey | 609
country | country_pkey | 604
film_actor | film_actor_pkey | 0
film_category | film_category_pkey | 0
film | film_pkey | 11043
inventory | inventory_pkey | 16048
(10 rows)
ืื ืืื ืืืืฉ ืฉื ืืื ืืงืกืื ืขื ืคืืืช ืื ืขืืืื
ืืขืชืื ืงืจืืืืช ืฆืจืื ืืื ืืช ืืืืฉ ืืื ืืงืกืื, ืืืฉื ืืฉืื ืืชื ืคืืื, ืืื ืืื ืืืืฉ ืืืืื ืืืืืฅ ืืช ืืกืจืืงื. ืื ืืื ืืงืกืื ืขืืืืื ืืืืคืื. ืฉืื ืื ืคืจืืืจื ืืืื ืืงืก ืขืฉืื ืืืจืืฉ ืื ืื ืืื ืืืืฉ ืฉืื.
ืืคืฉืจ ืืฆืืจืช ืืื ืืงืก ืืงืืื
ื-PostgreSQL 11, ืืฆืืจืช ืืื ืืงืก B-Tree ืืชืืฆืขืช ืืืงืืื. ืืื ืืืืืฅ ืืช ืชืืืื ืืืฆืืจื, ื ืืชื ืืืฉืชืืฉ ืืืกืคืจ ืขืืืืื ืืงืืืืื. ืขื ืืืช, ืืื ืฉืืคืฉืจืืืืช ืืชืฆืืจื ืืืื ืืืืืจืืช ืืืืื:
SET max_parallel_workers = 32;
SET max_parallel_maintenance_workers = 16;
ืขืจืื ืืจืืจืช ืืืืื ืงืื ืื ืืื. ืืืืคื ืืืืืืื, ืืกืคืจืื ืืื ืฆืจืืืื ืืืืื ืืื ืขื ืืกืคืจ ืืืืืช ืืืขืื. ืงืจื ืขืื ื
ืืฆืืจืช ืืื ืืงืก ืจืงืข
ื ืืชื ืืืฆืืจ ืืื ืืงืก ืืจืงืข ืืืืฆืขืืช ืืืคืฉืจืืช CONCURRENTLY
ืฆืืืชืื CREATE INDEX
:
pagila=# CREATE INDEX CONCURRENTLY idx_address1 ON address(district);
CREATE INDEX
ืืืื ืืฆืืจืช ืืื ืืงืก ืื ืฉืื ื ืืืจืืื ืืื ืฉืืื ืืื ื ืืฆืจืื ื ืขืืื ืขื ืืฉืืืื, ืืืื ืืื ื ืืืกื ืคืขืืืืช ืืชืืื. ืืฆื ืฉื ื, ืื ืืืงื ืืืชืจ ืืื ืืฆืืจื ืืืชืจ ืืฉืืืื.
Postgres ืืกืคืงืช ืืืืฉืืช ืจืื ืืืฆืืจืช ืืื ืืงืกืื ืืืจืืื ืืคืชืืจ ืื ืืงืจืื ืืืืืืื, ืืื ืื ืืจืืื ืื ืื ืืช ืืกื ืื ืชืื ืื ืืืงืจื ืฉืืืคืืืงืฆืื ืฉืื ืชืืื ืืฆืืจื ืืคืืฆืฆืช. ืื ื ืืงืืืื ืฉืืืืคืื ืืืื ืืขืืจื ืื ืืงืื ืืช ืืฉืืืืชืืช ืฉืื ืืืืืจืืช ืืืืกืืก ืื ืชืื ืื ืฉืื ืืืื ืืืจืืื.
ืืงืืจ: www.habr.com