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2013-05-29:使用最新配置和额外信息更新问题。早些时候我在一个 virtualbox 映像中进行测试。现在我正在生产服务器上进行测试,它更好地反映了现实世界。问题现在应该完全清楚了。如果您以前帮助过我,请仔细阅读

目前我发现 PostgreSQL 中的查询非常慢,但我不明白它怎么会很慢。我把它缩小了一点,所以在这里发布要小得多(而且速度更快,但仍然很慢!)。

小背景:在这个项目中,我有属于用户的广告。用户是该国某个区域的一部分。一个区域可以有多个子区域,因此区域表是一棵树。一个网络被分配给一个区域。在网络上过滤时,它应该过滤该区域及其树中的所有区域子项。因为我无法查询一棵无休止的树,所以我有一张可以压平这棵完整树的表格。

因此,通过 1 个查询(SELECT area_id FROM network_area_flatdeep WHERE network_id = 1),我得到了属于网络 1 的所有区域: 63, 64, 65, 66, 67, 68, 69, 70

这使得查询非常容易。

慢查询(在测试所有内容之前都已进行 VACUUM ANALYZED):

EXPLAIN ANALYZE SELECT a0_.id  AS id0
FROM   advert a0_
       INNER JOIN member m6_
               ON a0_.user_id = m6_.id
       INNER JOIN area a7_
               ON m6_.area_id = a7_.id
WHERE  a0_.status IN ( 1 )
       AND m6_.status IN ( 1 )
       AND a7_.id IN (SELECT area_id FROM network_area_flatdeep WHERE network_id IN (1))
ORDER  BY a0_.created_date DESC
LIMIT  60;
                                                                                 QUERY PLAN                                                                                  
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=41.10..34695.53 rows=60 width=12) (actual time=9.327..134.581 rows=60 loops=1)
   ->  Nested Loop  (cost=41.10..2291276.69 rows=3967 width=12) (actual time=9.326..134.534 rows=60 loops=1)
         Join Filter: (a7_.id = m6_.area_id)
         Rows Removed by Join Filter: 22566
         ->  Nested Loop  (cost=41.10..821630.16 rows=317633 width=24) (actual time=0.049..39.638 rows=22666 loops=1)
               ->  Index Scan Backward using advert_created_date_idx on advert a0_  (cost=0.00..762000.64 rows=317633 width=16) (actual time=0.013..4.357 rows=2834 loops=1)
                     Filter: (status = 1)
                     Rows Removed by Filter: 21
               ->  Materialize  (cost=41.10..73.38 rows=15 width=8) (actual time=0.000..0.004 rows=8 loops=2834)
                     ->  Nested Loop  (cost=41.10..73.30 rows=15 width=8) (actual time=0.031..0.073 rows=8 loops=1)
                           ->  HashAggregate  (cost=41.10..41.18 rows=8 width=4) (actual time=0.023..0.026 rows=8 loops=1)
                                 ->  Bitmap Heap Scan on network_area_flatdeep  (cost=4.37..41.06 rows=15 width=4) (actual time=0.011..0.015 rows=8 loops=1)
                                       Recheck Cond: (network_id = 1)
                                       ->  Bitmap Index Scan on idx_c29e880034128b91  (cost=0.00..4.36 rows=15 width=0) (actual time=0.007..0.007 rows=8 loops=1)
                                             Index Cond: (network_id = 1)
                           ->  Index Only Scan using area_pkey on area a7_  (cost=0.00..4.01 rows=1 width=4) (actual time=0.002..0.003 rows=1 loops=8)
                                 Index Cond: (id = network_area_flatdeep.area_id)
                                 Heap Fetches: 8
         ->  Index Scan using member_pkey on member m6_  (cost=0.00..4.61 rows=1 width=8) (actual time=0.002..0.003 rows=1 loops=22666)
               Index Cond: (id = a0_.user_id)
               Filter: (status = 1)
               Rows Removed by Filter: 0
 Total runtime: 134.698 ms
(23 rows)

子查询本身是:

EXPLAIN ANALYZE SELECT area_id FROM network_area_flatdeep WHERE network_id IN (1);
                                                        QUERY PLAN                                                          
------------------------------------------------------------------------------------------------------------------------------
 Bitmap Heap Scan on network_area_flatdeep  (cost=4.37..41.06 rows=15 width=4) (actual time=0.020..0.024 rows=8 loops=1)
   Recheck Cond: (network_id = 1)
   ->  Bitmap Index Scan on idx_c29e880034128b91  (cost=0.00..4.36 rows=15 width=0) (actual time=0.012..0.012 rows=8 loops=1)
         Index Cond: (network_id = 1)
 Total runtime: 0.051 ms
(5 rows)

这导致:63, 64, 65, 66, 67, 68, 69, 70

因此,我尝试在 id 中进行硬编码。并期望它更快(但不是):

EXPLAIN ANALYZE SELECT a0_.id  AS id0
FROM   advert a0_
       INNER JOIN member m6_
               ON a0_.user_id = m6_.id
       INNER JOIN area a7_
                   ON m6_.area_id = a7_.id
WHERE  a0_.status IN ( 1 )
       AND m6_.status IN ( 1 )
       AND a7_.id IN (63, 64, 65, 66, 67, 68, 69, 70)
ORDER  BY a0_.created_date DESC
LIMIT  60;
                                                                           QUERY PLAN                                                                           
----------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=17558.82..17558.97 rows=60 width=12) (actual time=56.594..56.670 rows=60 loops=1)
   ->  Sort  (cost=17558.82..17560.07 rows=498 width=12) (actual time=56.593..56.621 rows=60 loops=1)
         Sort Key: a0_.created_date
         Sort Method: top-N heapsort  Memory: 27kB
         ->  Nested Loop  (cost=0.00..17541.62 rows=498 width=12) (actual time=0.047..53.808 rows=4478 loops=1)
               ->  Nested Loop  (cost=0.00..3903.99 rows=286 width=4) (actual time=0.027..17.492 rows=8004 loops=1)
                     ->  Seq Scan on area a7_  (cost=0.00..144.78 rows=8 width=4) (actual time=0.007..0.823 rows=8 loops=1)
                           Filter: (id = ANY ('{63,64,65,66,67,68,69,70}'::integer[]))
                           Rows Removed by Filter: 5081
                     ->  Index Scan using idx_70e4fa78bd0f409c on member m6_  (cost=0.00..468.38 rows=152 width=8) (actual time=0.011..1.208 rows=1000 loops=8)
                           Index Cond: (area_id = a7_.id)
                           Filter: (status = 1)
                           Rows Removed by Filter: 2
               ->  Index Scan using idx_54f1f40ba76ed395 on advert a0_  (cost=0.00..47.49 rows=19 width=16) (actual time=0.002..0.003 rows=1 loops=8004)
                     Index Cond: (user_id = m6_.id)
                     Filter: (status = 1)
                     Rows Removed by Filter: 1
 Total runtime: 56.744 ms
(18 rows)

Time: 57.995 ms

我试图将子查询放在 INNER JOIN 中:

EXPLAIN ANALYZE SELECT a0_.id  AS id0
FROM   advert a0_
       INNER JOIN member m6_
               ON a0_.user_id = m6_.id
       INNER JOIN area a7_
               ON m6_.area_id = a7_.id 
               AND m6_.area_id IN (SELECT area_id FROM network_area_flatdeep WHERE network_id IN     (1))
WHERE  a0_.status IN ( 1 )
       AND m6_.status IN ( 1 )
ORDER  BY a0_.created_date DESC
LIMIT  60;
                                                                                QUERY PLAN                                                                                     
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=4.37..34966.73 rows=60 width=12) (actual time=2.957..42.443 rows=60 loops=1)
   ->  Nested Loop  (cost=4.37..2311599.10 rows=3967 width=12) (actual time=2.956..42.394 rows=60 loops=1)
         ->  Nested Loop Semi Join  (cost=4.37..2302173.51 rows=3967 width=20) (actual time=2.949..42.099 rows=60 loops=1)
               Join Filter: (m6_.area_id = network_area_flatdeep.area_id)
               Rows Removed by Join Filter: 22333
               ->  Nested Loop  (cost=0.00..2230853.09 rows=316797 width=16) (actual time=0.028..18.612 rows=2829 loops=1)
                     ->  Index Scan Backward using advert_created_date_idx on advert a0_  (cost=0.00..762000.64 rows=317633 width=16) (actual time=0.012..3.802 rows=2834 loops=1)
                           Filter: (status = 1)
                           Rows Removed by Filter: 21
                     ->  Index Scan using member_pkey on member m6_  (cost=0.00..4.61 rows=1 width=8) (actual time=0.003..0.003 rows=1 loops=2834)
                           Index Cond: (id = a0_.user_id)
                           Filter: (status = 1)
                           Rows Removed by Filter: 0
               ->  Materialize  (cost=4.37..41.14 rows=15 width=4) (actual time=0.000..0.004 rows=8 loops=2829)
                     ->  Bitmap Heap Scan on network_area_flatdeep  (cost=4.37..41.06 rows=15 width=4) (actual time=0.009..0.015 rows=8 loops=1)
                           Recheck Cond: (network_id = 1)
                           ->  Bitmap Index Scan on idx_c29e880034128b91  (cost=0.00..4.36 rows=15 width=0) (actual time=0.006..0.006 rows=8 loops=1)
                                 Index Cond: (network_id = 1)
         ->  Index Only Scan using area_pkey on area a7_  (cost=0.00..2.37 rows=1 width=4) (actual time=0.002..0.003 rows=1 loops=60)
               Index Cond: (id = m6_.area_id)
               Heap Fetches: 60
 Total runtime: 42.538 ms
(22 rows)

我试图摆脱子查询并做出正确的 JOIN 语句network_area_flatdeep(我非常喜欢这个版本):

EXPLAIN ANALYZE SELECT a0_.id  AS id0
FROM   advert a0_
       INNER JOIN member m6_
               ON a0_.user_id = m6_.id
       INNER JOIN area a7_
               ON m6_.area_id = a7_.id 
       INNER JOIN network_area_flatdeep n14_
               ON a7_.id = n14_.area_id
                  AND ( n14_.network_id IN ( 1 ) )
WHERE  a0_.status IN ( 1 )
       AND m6_.status IN ( 1 )
ORDER  BY a0_.created_date DESC
LIMIT  60;
                                                                                   QUERY PLAN                                                                                    
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=30031.18..30031.33 rows=60 width=12) (actual time=62.968..63.045 rows=60 loops=1)
   ->  Sort  (cost=30031.18..30033.51 rows=934 width=12) (actual time=62.967..62.991 rows=60 loops=1)
         Sort Key: a0_.created_date
         Sort Method: top-N heapsort  Memory: 27kB
         ->  Nested Loop  (cost=0.00..29998.92 rows=934 width=12) (actual time=0.157..60.280 rows=4478 loops=1)
               ->  Nested Loop  (cost=0.00..4401.66 rows=536 width=4) (actual time=0.029..20.488 rows=8004 loops=1)
                     ->  Nested Loop  (cost=0.00..120.69 rows=15 width=8) (actual time=0.015..0.084 rows=8 loops=1)
                           ->  Index Scan using idx_c29e880034128b91 on network_area_flatdeep n14_  (cost=0.00..60.47 rows=15 width=4) (actual time=0.009..0.019 rows=8 loops=1)
                                 Index Cond: (network_id = 1)
                           ->  Index Only Scan using area_pkey on area a7_  (cost=0.00..4.01 rows=1 width=4) (actual time=0.004..0.005 rows=1 loops=8)
                                 Index Cond: (id = n14_.area_id)
                                 Heap Fetches: 8
                     ->  Index Scan using idx_70e4fa78bd0f409c on member m6_  (cost=0.00..283.88 rows=152 width=8) (actual time=0.011..1.278 rows=1000 loops=8)
                           Index Cond: (area_id = a7_.id)
                           Filter: (status = 1)
                           Rows Removed by Filter: 2
               ->  Index Scan using idx_54f1f40ba76ed395 on advert a0_  (cost=0.00..47.57 rows=19 width=16) (actual time=0.003..0.003 rows=1 loops=8004)
                     Index Cond: (user_id = m6_.id)
                     Filter: (status = 1)
                     Rows Removed by Filter: 1
 Total runtime: 63.125 ms
(21 rows)

更改IN=也无济于事。

我尝试按照 wilderplasser 的建议使用 EXISTS,并在下面给出答案。

当我删除 ORDER BY 或网络条件时,查询速度很快(2 毫秒)。但是为什么他们不能一起玩得很好呢?

现在……当我将 network_id 从“1”更改为“10”时。查询速度非常快,就像我想要的那样。10 是包含所有区域的根网络。因此,显然 JOIN 需要过滤掉的结果越少,查询就越快。

结构如下所示:

area (mapped to network 10 which contains 5089 areas in flat table and is FAST)
|    |---- area 1 (network 1 which contains 8 areas in flat table and is SLOW)
|        |--- more areas
|-- ALOT MORE areas
|-- etc

将网络 1 更改为 10 给出:3.265 ms

总结一下区别:

网络 1 有 8 个区域network_area_flatdeep 网络 10 有 5089 个区域network_area_flatdeep

所以使用网络 1 的 INNER JOIN 非常慢,使用网络 10 的 INNER JOIN 非常快。子查询的行为相同。

广告表

353804 rows
                                                                   Table "public.advert"
           Column            |              Type              |                      Modifiers                      | Storage  | Stats target | Description 
-----------------------------+--------------------------------+-----------------------------------------------------+----------+--------------+-------------
 id                          | integer                        | not null default nextval('advert_id_seq'::regclass) | plain    |              | 
 user_id                     | integer                        | not null                                            | plain    |              | 
 advert_category_id          | integer                        | not null                                            | plain    |              | 
 currency_id                 | integer                        | not null                                            | plain    |              | 
 advert_kind_id              | integer                        | not null                                            | plain    |              | 
 advert_price_id             | integer                        |                                                     | plain    |              | 
 external_source_id          | integer                        |                                                     | plain    |              | 
 status                      | integer                        | not null                                            | plain    |              | 
 type                        | integer                        | not null                                            | plain    |              | 
 title                       | character varying(60)          | not null                                            | extended |              | 
 description                 | text                           | not null                                            | extended |              | 
 price                       | numeric(19,2)                  | default NULL::numeric                               | main     |              | 
 accepting_bids              | boolean                        | not null                                            | plain    |              | 
 promoted                    | boolean                        | not null                                            | plain    |              | 
 edited_date                 | timestamp(0) without time zone | default NULL::timestamp without time zone           | plain    |              | 
 created_date                | timestamp(0) without time zone | not null                                            | plain    |              | 
 archived_date               | timestamp(0) without time zone | default NULL::timestamp without time zone           | plain    |              | 
 views                       | integer                        | not null                                            | plain    |              | 
 checked_date                | timestamp(0) without time zone | default NULL::timestamp without time zone           | plain    |              | 
 archived_by_cron            | boolean                        | not null                                            | plain    |              | 
 unarchived_by_cron          | boolean                        | not null                                            | plain    |              | 
 containting_forbidden_words | boolean                        | not null                                            | plain    |              | 
 external_id                 | character varying(255)         | default NULL::character varying                     | extended |              | 
 new_product                 | boolean                        | not null                                            | plain    |              | 
Indexes:
    "advert_pkey" PRIMARY KEY, btree (id)
    "advert_external_idx_uq" UNIQUE, btree (external_id, external_source_id)
    "advert_archived_date_idx" btree (archived_date)
    "advert_checked_date_idx" btree (checked_date)
    "advert_created_date_idx" btree (created_date)
    "advert_edited_date_idx" btree (edited_date)
    "advert_external_id_idx" btree (external_id)
    "advert_price_idx" btree (price)
    "advert_status_idx" btree (status)
    "advert_type_idx" btree (type)
    "advert_views_idx" btree (views)
    "idx_54f1f40b38248176" btree (currency_id)
    "idx_54f1f40b54b67d66" btree (advert_price_id)
    "idx_54f1f40b9a2e6cff" btree (advert_kind_id)
    "idx_54f1f40ba76ed395" btree (user_id)
    "idx_54f1f40bb167b375" btree (external_source_id)
    "idx_54f1f40bd4436821" btree (advert_category_id)
Foreign-key constraints:
    "fk_54f1f40b38248176" FOREIGN KEY (currency_id) REFERENCES currency(id) ON DELETE RESTRICT
    "fk_54f1f40b54b67d66" FOREIGN KEY (advert_price_id) REFERENCES advertprice(id) ON DELETE RESTRICT
    "fk_54f1f40b9a2e6cff" FOREIGN KEY (advert_kind_id) REFERENCES advertkind(id) ON DELETE RESTRICT
    "fk_54f1f40ba76ed395" FOREIGN KEY (user_id) REFERENCES member(id) ON DELETE CASCADE
    "fk_54f1f40bb167b375" FOREIGN KEY (external_source_id) REFERENCES externalsource(id) ON DELETE RESTRICT
    "fk_54f1f40bd4436821" FOREIGN KEY (advert_category_id) REFERENCES advertcategory(id) ON DELETE RESTRICT
Referenced by:
    TABLE "advert_photo" CONSTRAINT "fk_1c939974d07eccb6" FOREIGN KEY (advert_id) REFERENCES advert(id) ON DELETE CASCADE
    TABLE "banner" CONSTRAINT "fk_6f9db8e7d07eccb6" FOREIGN KEY (advert_id) REFERENCES advert(id) ON DELETE SET NULL
    TABLE "advertbid" CONSTRAINT "fk_fccdba75d07eccb6" FOREIGN KEY (advert_id) REFERENCES advert(id) ON DELETE CASCADE
Has OIDs: no

面积表:

5089 rows
                                               Table "public.area"
   Column   |  Type   |                     Modifiers                     | Storage | Stats target | Description 
------------+---------+---------------------------------------------------+---------+--------------+-------------
 id         | integer | not null default nextval('area_id_seq'::regclass) | plain   |              | 
 network_id | integer |                                                   | plain   |              | 
 parent_id  | integer |                                                   | plain   |              | 
 selectable | boolean | not null                                          | plain   |              | 
Indexes:
    "area_pkey" PRIMARY KEY, btree (id)
    "idx_d7943d6834128b91" btree (network_id)
    "idx_d7943d68727aca70" btree (parent_id)
Foreign-key constraints:
    "fk_d7943d6834128b91" FOREIGN KEY (network_id) REFERENCES network(id) ON DELETE RESTRICT
    "fk_d7943d68727aca70" FOREIGN KEY (parent_id) REFERENCES area(id) ON DELETE CASCADE
Referenced by:
    TABLE "network_area_flat" CONSTRAINT "fk_10aae5b2bd0f409c" FOREIGN KEY (area_id) REFERENCES area(id) ON DELETE CASCADE
    TABLE "area_language" CONSTRAINT "fk_17d42f7dbd0f409c" FOREIGN KEY (area_id) REFERENCES area(id) ON DELETE CASCADE
    TABLE "area_zip_code" CONSTRAINT "fk_62a3bf90bd0f409c" FOREIGN KEY (area_id) REFERENCES area(id) ON DELETE CASCADE
    TABLE "member" CONSTRAINT "fk_70e4fa78bd0f409c" FOREIGN KEY (area_id) REFERENCES area(id) ON DELETE RESTRICT
    TABLE "network_area_flatdeep" CONSTRAINT "fk_c29e8800bd0f409c" FOREIGN KEY (area_id) REFERENCES area(id) ON DELETE CASCADE
    TABLE "area" CONSTRAINT "fk_d7943d68727aca70" FOREIGN KEY (parent_id) REFERENCES area(id) ON DELETE CASCADE
Has OIDs: no

成员表:

182450 rows
                                                               Table "public.member"
        Column         |              Type              |                      Modifiers                      | Storage  | Stats target | Description 
-----------------------+--------------------------------+-----------------------------------------------------+----------+--------------+-------------
 id                    | integer                        | not null default nextval('member_id_seq'::regclass) | plain    |              | 
 language_id           | integer                        | not null                                            | plain    |              | 
 area_id               | integer                        | not null                                            | plain    |              | 
 company_id            | integer                        |                                                     | plain    |              | 
 external_source_id    | integer                        |                                                     | plain    |              | 
 email                 | character varying(255)         | not null                                            | extended |              | 
 password              | character varying(40)          | not null                                            | extended |              | 
 status                | integer                        | not null                                            | plain    |              | 
 name                  | character varying(150)         | not null                                            | extended |              | 
 zip_code              | character varying(20)          |                                                     | extended |              | 
 phone_number          | character varying(120)         | default NULL::character varying                     | extended |              | 
 using_email_service   | boolean                        | not null                                            | plain    |              | 
 edited_date           | timestamp(0) without time zone | default NULL::timestamp without time zone           | plain    |              | 
 created_date          | timestamp(0) without time zone | not null                                            | plain    |              | 
 hiding_on_own_network | boolean                        | not null                                            | plain    |              | 
 staff                 | boolean                        | not null                                            | plain    |              | 
 superuser             | boolean                        | not null                                            | plain    |              | 
 external_id           | character varying(255)         | default NULL::character varying                     | extended |              | 
 last_login_date       | timestamp(0) without time zone | default NULL::timestamp without time zone           | plain    |              | 
 deleted_adverts       | integer                        | not null                                            | plain    |              | 
Indexes:
    "member_pkey" PRIMARY KEY, btree (id)
    "user_email_idx_uq" UNIQUE, btree (email)
    "user_external_idx_uq" UNIQUE, btree (external_id, external_source_id)
    "idx_70e4fa7882f1baf4" btree (language_id)
    "idx_70e4fa78979b1ad6" btree (company_id)
    "idx_70e4fa78b167b375" btree (external_source_id)
    "idx_70e4fa78bd0f409c" btree (area_id)
    "user_external_id_idx" btree (external_id)
    "user_name_idx" btree (name)
    "user_status_idx" btree (status)
Foreign-key constraints:
    "fk_70e4fa7882f1baf4" FOREIGN KEY (language_id) REFERENCES language(id) ON DELETE RESTRICT
    "fk_70e4fa78979b1ad6" FOREIGN KEY (company_id) REFERENCES company(id) ON DELETE SET NULL
    "fk_70e4fa78b167b375" FOREIGN KEY (external_source_id) REFERENCES externalsource(id) ON DELETE RESTRICT
    "fk_70e4fa78bd0f409c" FOREIGN KEY (area_id) REFERENCES area(id) ON DELETE RESTRICT
Referenced by:
    TABLE "user_link" CONSTRAINT "fk_4c2dd538a76ed395" FOREIGN KEY (user_id) REFERENCES member(id) ON DELETE CASCADE
    TABLE "advert" CONSTRAINT "fk_54f1f40ba76ed395" FOREIGN KEY (user_id) REFERENCES member(id) ON DELETE CASCADE
    TABLE "banner" CONSTRAINT "fk_6f9db8e7a76ed395" FOREIGN KEY (user_id) REFERENCES member(id) ON DELETE SET NULL
    TABLE "user_admin_module_permission" CONSTRAINT "fk_74fee7cea76ed395" FOREIGN KEY (user_id) REFERENCES member(id) ON DELETE CASCADE
    TABLE "user_admin_resource_permission" CONSTRAINT "fk_c9fcf279a76ed395" FOREIGN KEY (user_id) REFERENCES member(id) ON DELETE CASCADE
Has OIDs: no

Network_area_flatdeep 表:

10177 rows
                                                           Table "public.network_area_flatdeep"
    Column    |              Type              |                             Modifiers                              | Storage | Stats target | Description 
--------------+--------------------------------+--------------------------------------------------------------------+---------+--------------+-------------
 id           | integer                        | not null default nextval('network_area_flatdeep_id_seq'::regclass) | plain   |              | 
 network_id   | integer                        | not null                                                           | plain   |              | 
 area_id      | integer                        | not null                                                           | plain   |              | 
 created_date | timestamp(0) without time zone | not null                                                           | plain   |              | 
Indexes:
    "network_area_flatdeep_pkey" PRIMARY KEY, btree (id)
    "area_flatdeep_idx_uq" UNIQUE, btree (area_id, network_id, created_date)
    "idx_c29e880034128b91" btree (network_id)
    "idx_c29e8800bd0f409c" btree (area_id)
Foreign-key constraints:
    "fk_c29e880034128b91" FOREIGN KEY (network_id) REFERENCES network(id) ON DELETE CASCADE
    "fk_c29e8800bd0f409c" FOREIGN KEY (area_id) REFERENCES area(id) ON DELETE CASCADE
Has OIDs: no

简短的服务器配置:

                                                   version                                                    
--------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.2.4 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-3), 64-bit

            name            |  current_setting   |        source        
----------------------------+--------------------+----------------------
 shared_buffers             | 1800MB             | configuration file
 work_mem                   | 4MB                | configuration file

结论:

数据越多(过滤掉的越少),查询速度就越快。我现在有点不知所措。PostgreSQL 怎么会这么慢?再说一遍:40ms 看起来并不是特别慢,但是对于带有大 SELECT 语句的实际查询,查询大部分时间是 1.5 秒,最多可能需要 3 秒。

所有过滤都是在索引上完成的。排序也是在索引上完成的。

有谁知道如何改进这个我显然需要分离数据的简单过滤器?

4

4 回答 4

2

尝试用IN(subquery)相应的替换EXISTS(correlated subquery)

SELECT a0_.id  AS id0
FROM   advert a0_
INNER JOIN member m6_
               ON a0_.user_id = m6_.id
INNER JOIN area a7_
               ON m6_.area_id = a7_.id 
WHERE a0_.status IN ( 1 )
AND m6_.status IN ( 1 )
AND EXISTS (
     SELECT*
     FROM network_area_flatdeep xx
     WHERE xx.area_id = m6_.area_id
     AND xx.network_id IN  (2)
     )
ORDER  BY a0_.created_date DESC
LIMIT  60
   ;

你当然需要主键和相关的外键。我不知道network_area_flatdeep.area_id,如果它不是 PK 或 FK,您可能需要一个索引(或使其成为复合 PK 的一部分)

更新:带有合成数据的测试平台:

DROP SCHEMA tmp CASCADE;
CREATE SCHEMA tmp ;
SET search_path=tmp;

CREATE Table area
 ( id   SERIAL  not null PRIMARY KEY
 , zzzz varchar
        );

CREATE Table member
 ( id   SERIAL  not null PRIMARY KEY
 , language_id  integer not null DEFAULT 0
 , area_id      integer not null REFERENCES area(id)
 , company_id   integer
 , external_source_id   integer
 , status       integer not null  DEFAULT 0
 , name varchar not null
 , zip_code     varchar not null
 , phone_number varchar default NULL
 , using_email_service  boolean not null DEFAULT False
 , edited_date  timestamp(0) without time zone  default NULL
 , created_date timestamp(0) without time zone  not null
 , hiding_on_own_network        boolean not null DEFAULT False
 , staff        boolean not null DEFAULT False
 , superuser    boolean not null DEFAULT False
 , external_id  varchar default NULL
        );

CREATE TABLE advert
 ( id   SERIAL NOT NULL PRIMARY KEY
 , user_id      integer NOT NULL  REFERENCES member(id)
 , advert_category_id   integer NOT NULL DEFAULT 0
 , currency_id  integer NOT NULL DEFAULT 0
 , advert_kind_id       integer NOT NULL DEFAULT 0
 , advert_price_id      integer
 , external_source_id   integer
 , status       integer NOT NULL DEFAULT 0
 , type integer NOT NULL DEFAULT 0
 , title        varchar NOT NULL
 , description  text NOT NULL
 , price        numeric(10,2) default NULL
 , accepting_bids       boolean NOT NULL DEFAULT False
 , promoted     boolean NOT NULL  DEFAULT False
 , edited_date  timestamp(0) without time zone default NULL
 , created_date timestamp(0) without time zone NOT NULL
 , archived_date        timestamp(0) without time zone  default NULL
 , views        integer NOT NULL  DEFAULT 0
 , checked_date timestamp(0) without time zone default NULL
 , archived_by_cron     boolean NOT NULL  DEFAULT False
 , unarchived_by_cron   boolean NOT NULL  DEFAULT False
 , containting_forbidden_words  boolean NOT NULL  DEFAULT False
 , external_id  varchar default NULL
        );

CREATE INDEX advert_created_date_idx ON advert (created_date);

CREATE Table network_area_flatdeep
        -- the surrogate key in a junction table is questionable
 ( id   SERIAL not null PRIMARY KEY
 , network_id   integer not null -- REFERENCES network(id) ON DELETE CASCADE
 , area_id      integer not null REFERENCES area(id) ON DELETE CASCADE
 , created_date timestamp(0) without time zone not null
        -- the date in the below constraint is questionable
 , CONSTRAINT area_flatdeep_idx_uq UNIQUE (area_id, network_id, created_date)
        );
CREATE INDEX idx_c29e880034128b91 ON network_area_flatdeep(network_id);
CREATE INDEX idx_c29e8800bd0f409c ON network_area_flatdeep(area_id);
INSERT INTO area ( zzzz)
SELECT 'Zzzz_' || gs::text
FROM generate_series(1,39) gs
        ;

INSERT INTO network_area_flatdeep
        -- the surrogate key in a junction table is questionable
 ( network_id , area_id , created_date)
SELECT gs % 7 , aa.id, now()
FROM generate_series(1,76) gs
JOIN area aa ON aa.id = 1+gs % 39
        ;


INSERT INTO member
 ( area_id , name , zip_code, created_date)
SELECT aa.id
        , 'Member_'|| gs::text
        , 'Code_'|| gs::text
        , now()
FROM generate_series(1, 10086) gs
JOIN area aa ON aa.id = 1 + gs % 39
        ;
INSERT INTO advert( user_id , title, description, edited_date , created_date)
SELECT 1+ (gs* 321) % 10086
        , 'Tit_'|| gs::text
        , 'Desc_'|| gs::text
        , now()
        , now() - (random() * 10000 * '1 sec'::interval)
 from generate_series(1,47569 ) gs
        ;

UPDATE member SET status = 1 WHERE random() < .3;
UPDATE advert SET status = 1 WHERE random() < .3;

VACUUM ANALYZE member;
VACUUM ANALYZE advert;
VACUUM ANALYZE area;
VACUUM ANALYZE network_area_flatdeep;

我的查询在 12 毫秒 (PG-9.1) 内执行,计划与 OP 相同。(所以这一定是配置问题)

于 2013-04-10T14:52:59.447 回答
1

当您删除明显不必要的(并因此分散注意力的)加入区域时,您会得到什么样的计划?

SELECT a0_.id  AS id0
FROM   advert a0_
       INNER JOIN member m6_
               ON a0_.user_id = m6_.id
WHERE  a0_.status IN ( 1 )
       AND m6_.status IN ( 1 )
       AND m6_.area_id IN (SELECT area_id FROM network_area_flatdeep WHERE network_id IN (1))
ORDER  BY a0_.created_date DESC
LIMIT  60;
于 2013-05-30T00:03:31.153 回答
0

如果你把查询转过来会发生什么?因此,首先您选择区域,然后加入成员并在该区域上投放广告。您还可以通过JOIN直接添加 WHERE 部分来限制连接。

SELECT a0_.id  AS id0

FROM    area a7_
        LEFT JOIN member m6_
            ON a7_.id = m6_.area_id AND m6_.status IN ( 1 )
        LEFT JOIN advert a0_
            ON m6_.id = a0_.user_id

WHERE   a7_.id IN (SELECT area_id FROM network_area_flatdeep WHERE network_id IN (1))
        AND a0_.status IN ( 1 )

ORDER  BY a0_.created_date DESC
LIMIT  60;
于 2013-05-29T14:35:43.553 回答
0

您的一个查询的一个小变化

SELECT a0_.id  AS id0
FROM   advert a0_
       INNER JOIN member m6_
               ON a0_.user_id = m6_.id
       INNER JOIN area a7_
               ON m6_.area_id = a7_.id 
       INNER JOIN (
                SELECT area_id
                FROM network_area_flatdeep
                WHERE network_id IN (2)
                ) network_area_flatdeep n14_
               ON a7_.id = n14_.area_id
WHERE  a0_.status IN ( 1 )
       AND m6_.status IN ( 1 )
ORDER  BY a0_.created_date DESC
LIMIT  60;
于 2013-05-29T11:35:05.457 回答