Quindi ho questa tabella con 6,2 milioni di record e devo eseguire query di ricerca con somiglianza con una per la colonna. Le query possono essere:
SELECT "lca_test".* FROM "lca_test"
WHERE (similarity(job_title, 'sales executive') > 0.6)
AND worksite_city = 'los angeles'
ORDER BY salary ASC LIMIT 50 OFFSET 0
Altre condizioni possono essere aggiunte nel dove (anno = X, worksite_state = N, status = 'certificato', visa_class = Z).
L'esecuzione di alcune di queste query può richiedere molto tempo, oltre 30 secondi. A volte più di un minuto.
EXPLAIN ANALYZE
della query menzionata in precedenza mi dà questo:
Limit (cost=0.43..42523.04 rows=50 width=254) (actual time=9070.268..33487.734 rows=2 loops=1) -> Index Scan using index_lca_test_on_salary on lca_test (cost=0.43..23922368.16 rows=28129 width=254) (actual time=9070.265..33487.727 rows=2 loops=1) >>>> Filter: (((worksite_city)::text = 'los angeles'::text) AND (similarity((job_title)::text, 'sales executive'::text) > 0.6::double precision)) >>>> Rows Removed by Filter: 6330130 Total runtime: 33487.802 ms Total runtime: 33487.802 ms
Non riesco a capire come dovrei indicizzare la mia colonna per renderla velocissima.
EDIT: Ecco la versione di postgres:
PostgreSQL 9.3.5 su x86_64-unknown-linux-gnu, compilato da gcc (Debian 4.7.2-5) 4.7.2, 64-bit
Ecco la definizione della tabella:
Table "public.lca_test"
Column | Type | Modifiers | Storage | Stats target | Description
------------------------+-------------------+-------------------------------------------------------+----------+--------------+-------------
id | integer | not null default nextval('lca_test_id_seq'::regclass) | plain | |
raw_id | integer | | plain | |
year | integer | | plain | |
company_id | integer | | plain | |
visa_class | character varying | | extended | |
employement_start_date | character varying | | extended | |
employement_end_date | character varying | | extended | |
employer_name | character varying | | extended | |
employer_address1 | character varying | | extended | |
employer_address2 | character varying | | extended | |
employer_city | character varying | | extended | |
employer_state | character varying | | extended | |
employer_postal_code | character varying | | extended | |
employer_phone | character varying | | extended | |
employer_phone_ext | character varying | | extended | |
job_title | character varying | | extended | |
soc_code | character varying | | extended | |
naic_code | character varying | | extended | |
prevailing_wage | character varying | | extended | |
pw_unit_of_pay | character varying | | extended | |
wage_unit_of_pay | character varying | | extended | |
worksite_city | character varying | | extended | |
worksite_state | character varying | | extended | |
worksite_postal_code | character varying | | extended | |
total_workers | integer | | plain | |
case_status | character varying | | extended | |
case_no | character varying | | extended | |
salary | real | | plain | |
salary_max | real | | plain | |
prevailing_wage_second | real | | plain | |
lawyer_id | integer | | plain | |
citizenship | character varying | | extended | |
class_of_admission | character varying | | extended | |
Indexes:
"lca_test_pkey" PRIMARY KEY, btree (id)
"index_lca_test_on_id_and_salary" btree (id, salary)
"index_lca_test_on_id_and_salary_and_year" btree (id, salary, year)
"index_lca_test_on_id_and_salary_and_year_and_wage_unit_of_pay" btree (id, salary, year, wage_unit_of_pay)
"index_lca_test_on_id_and_visa_class" btree (id, visa_class)
"index_lca_test_on_id_and_worksite_state" btree (id, worksite_state)
"index_lca_test_on_lawyer_id" btree (lawyer_id)
"index_lca_test_on_lawyer_id_and_company_id" btree (lawyer_id, company_id)
"index_lca_test_on_raw_id_and_visa_and_pw_second" btree (raw_id, visa_class, prevailing_wage_second)
"index_lca_test_on_raw_id_and_visa_class" btree (raw_id, visa_class)
"index_lca_test_on_salary" btree (salary)
"index_lca_test_on_visa_class" btree (visa_class)
"index_lca_test_on_wage_unit_of_pay" btree (wage_unit_of_pay)
"index_lca_test_on_worksite_state" btree (worksite_state)
"index_lca_test_on_year_and_company_id" btree (year, company_id)
"index_lca_test_on_year_and_company_id_and_case_status" btree (year, company_id, case_status)
"index_lcas_job_title_trigram" gin (job_title gin_trgm_ops)
"lca_test_company_id" btree (company_id)
"lca_test_employer_name" btree (employer_name)
"lca_test_id" btree (id)
"lca_test_on_year_and_companyid_and_wage_unit_and_salary" btree (year, company_id, wage_unit_of_pay, salary)
Foreign-key constraints:
"fk_rails_8a90090fe0" FOREIGN KEY (lawyer_id) REFERENCES lawyers(id)
Has OIDs: no
worksite_city
, worksite_state
, year
e / o status
worksite_city
.