如何强制 PostgreSQL 在加入之前先查询小集以使查询更快？

Question

假设我有一个像下面这样的table

create table recommendation_raw_v2
(
    id                uuid          default gen_random_uuid() constraint recommendation_pkey primary key,
    worker_id         uuid                                        not null,
    company_id        uuid                                        not null,
    job_id            uuid                                        not null,
    obsolete          boolean       default false                 not null,
    discipline        varchar       default ''::character varying not null,
    weekly_pay_amount numeric(12, 4) default 0                     not null,
    geog              geography(Point, 4326)                      not null
);

我想找到所有 job_id 具有某些条件并且它们在 (-118.2436849, 34.0522342) 500 公里半径范围内。我创建一个查询

select A.weekly_pay_amount,
    , ST_Distance(c.x::geography, t.geog::geography)/1000 as distance
, A.job_id
from (
    select id, job_id, matching_score, weekly_pay_amount, job_created_at
        from recommendation_raw_v2
        where worker_id='89b9d5c1-3862-4820-887c-0f1b266e6ce8'::uuid
        and company_id='9fcf4081-4adb-4aaf-bf86-f4926de332ef'::uuid
        and obsolete = false
            and  weekly_pay_amount >= 500
            and discipline='Foo'
) as A
    join recommendation_raw_v2 as t on A.id = t.id,
        (SELECT ST_SetSRID(ST_MakePoint(-118.2436849, 34.0522342), 4326)) AS c(x)
        where ST_DWithin(t.geog::geography, c.x::geography, 500 * 1000)
order by 1 DESC;

我分析了这个查询

    QUERY PLAN
-------------------------------------------------------------------------------------
 Sort  (cost=1098.60..1098.61 rows=1 width=41) (actual time=182052.024..182053.516 rows=202 loops=1)
   Sort Key: recommendation_raw_v2.matching_score DESC
   Sort Method: quicksort  Memory: 40kB
   ->  Hash Join  (cost=1033.35..1098.59 rows=1 width=41) (actual time=1055.329..182050.122 rows=202 loops=1)
         Hash Cond: (t.id = recommendation_raw_v2.id)
         ->  Index Scan using gist_geog on recommendation_raw_v2 t  (cost=0.67..33.69 rows=2753 width=48) (actual time=564.032..181600.874 rows=1919272 loops=1)
               Index Cond: (geog && _st_expand('0101000020E6100000DC018D88988F5DC0CA5D3A9CAF064140'::geography, '500000'::double precision))
               Filter: st_dwithin(geog, '0101000020E6100000DC018D88988F5DC0CA5D3A9CAF064140'::geography, '500000'::double precision, true)
               Rows Removed by Filter: 1041991
         ->  Hash  (cost=1029.49..1029.49 rows=255 width=49) (actual time=31.253..32.173 rows=310 loops=1)
               Buckets: 1024  Batches: 1  Memory Usage: 35kB
               ->  Index Scan using worker_id_obsolete_index on recommendation_raw_v2  (cost=0.56..1029.49 rows=255 width=49) (actual time=1.883..31.102 rows=310 loops=1)
                     Index Cond: ((worker_id = '89b9d5c1-3862-4820-887c-0f1b266e6ce8'::uuid) AND (obsolete = false))
                     Filter: ((weekly_pay_amount >= '500'::numeric) AND (company_id = '9fcf4081-4adb-4aaf-bf86-f4926de332ef'::uuid) AND ((discipline)::text = 'Foo'::text))
                     Rows Removed by Filter: 148
 Planning Time: 16.259 ms
 Execution Time: 182058.761 ms

我看到有两部分，先gist_geog索引得到1919272行，worker_id_obsolete_index索引提取255行。 PostgreSQL 会将 2 个部分哈希连接在一起以产生最终结果。

我的问题是，如果我能以某种方式强制 PostgreSQL 首先执行 worker_id_obsolete_index，我的查询会更快吗？如果是，您有什么建议吗？

已更新：

PostgreSQL 12.5
PostgreGIS 3.0 USE_GEOS=1 USE_PROJ=1 USE_STATS=1

Answer 1

请原谅我过于简单化了你的问题，但既然你加入了一个 table 和它自己的一个子集，那么将所有内容放在一个查询中并让 planer 会不会更便宜决定做什么？

SELECT 
  job_id,weekly_pay_amount,
  ST_Distance(geog, 
    ST_SetSRID(ST_MakePoint(-118.2436849,34.0522342),4326)::geography)/1000
FROM recommendation_raw_v2
WHERE
  worker_id='89b9d5c1-3862-4820-887c-0f1b266e6ce8'::uuid AND
  company_id='9fcf4081-4adb-4aaf-bf86-f4926de332ef'::uuid AND
  obsolete = false AND
  weekly_pay_amount >= 500 AND
  discipline='Foo' AND
  ST_DWithin(geog, 
    ST_SetSRID(ST_MakePoint(-118.2436849,34.0522342),4326)::geography,500*1000);

如何强制 PostgreSQL 在加入之前先查询小集以使查询更快？

How to Force PostgreSQL query small set first before join to make query faster?

sql

postgresql

postgis

query-optimization