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我试图让这个查询运行得更快。似乎按质量字段排序是真正减慢速度的原因（表有大约 500 万行）-也许有一个索引我可以使用？

询问：

SELECT "connectr_twitterpassage"."id", "connectr_twitterpassage"."third_party_id", "connectr_twitterpassage"."third_party_created", "connectr_twitterpassage"."source", "connectr_twitterpassage"."text", "connectr_twitterpassage"."author", "connectr_twitterpassage"."raw_data", "connectr_twitterpassage"."retweet_count", "connectr_twitterpassage"."favorited_count", "connectr_twitterpassage"."lang", "connectr_twitterpassage"."location", "connectr_twitterpassage"."author_followers_count", "connectr_twitterpassage"."is_retweet", "connectr_twitterpassage"."url", "connectr_twitterpassage"."author_fk_id", "connectr_twitterpassage"."quality", "connectr_twitterpassage"."is_top_tweet", "connectr_twitterpassage"."created", "connectr_twitterpassage"."modified" 
FROM "connectr_twitterpassage" 
INNER JOIN "connectr_twitterpassage_words" ON ("connectr_twitterpassage"."id" = "connectr_twitterpassage_words"."twitterpassage_id") 
WHERE "connectr_twitterpassage_words"."word_id" = 18974807  
ORDER BY "connectr_twitterpassage"."quality" 
DESC LIMIT 100

这是解释分析：http: //explain.depesz.com/s/7zb

和表定义：

\d connectr_twitterpassage

             Column         |           Type           |                              Modifiers                               
    ------------------------+--------------------------+----------------------------------------------------------------------
     id           

      | integer                  | not null default nextval('connectr_twitterpassage_id_seq'::regclass)
 third_party_id         | character varying(10000) | not null
 source                 | character varying(10000) | not null
 text                   | character varying(10000) | not null
 author                 | character varying(10000) | not null
 raw_data               | character varying(10000) | not null
 created                | timestamp with time zone | not null
 modified               | timestamp with time zone | not null
 third_party_created    | timestamp with time zone | 
 retweet_count          | integer                  | not null
 favorited_count        | integer                  | not null
 lang                   | character varying(10000) | not null
 location               | character varying(10000) | not null
 author_followers_count | integer                  | not null
 is_retweet             | boolean                  | not null
 url                    | character varying(10000) | not null
 author_fk_id           | integer                  | 
 quality                | bigint                   | 
 is_top_tweet           | boolean                  | not null
Indexes:
    "connectr_passage_pkey" PRIMARY KEY, btree (id)
    "connectr_twitterpassage_third_party_id_uniq" UNIQUE CONSTRAINT, btree (third_party_id)
    "connectr_passage_author_followers_count" btree (author_followers_count)
    "connectr_passage_favorited_count" btree (favorited_count)
    "connectr_passage_retweet_count" btree (retweet_count)
    "connectr_passage_source" btree (source)
    "connectr_passage_source_like" btree (source varchar_pattern_ops)
    "connectr_passage_third_party_id" btree (third_party_id)
    "connectr_passage_third_party_id_like" btree (third_party_id varchar_pattern_ops)
    "connectr_twitterpassage_author_fk_id" btree (author_fk_id)
    "connectr_twitterpassage_created" btree (created)
    "connectr_twitterpassage_is_top_tweet" btree (is_top_tweet)
    "connectr_twitterpassage_quality" btree (quality)
    "connectr_twitterpassage_third_party_created" btree (third_party_created)
    "id_to_quality_sorted" btree (id, quality DESC NULLS LAST)
Foreign-key constraints:
    "author_fk_id_refs_id_074720a5" FOREIGN KEY (author_fk_id) REFERENCES connectr_twitteruser(id) DEFERRABLE INITIALLY DEFERRED
Referenced by:
    TABLE "connectr_passageviewevent" CONSTRAINT "passage_id_refs_id_892b36a6" FOREIGN KEY (passage_id) REFERENCES connectr_twitterpassage(id) DEFERRABLE INITIALLY DEFERRED
    TABLE "connectr_connection" CONSTRAINT "twitter_from_id_refs_id_8adbab24" FOREIGN KEY (twitter_from_id) REFERENCES connectr_twitterpassage(id) DEFERRABLE INITIALLY DEFERRED
    TABLE "connectr_connection" CONSTRAINT "twitter_to_id_refs_id_8adbab24" FOREIGN KEY (twitter_to_id) REFERENCES connectr_twitterpassage(id) DEFERRABLE INITIALLY DEFERRED
    TABLE "connectr_twitterpassage_words" CONSTRAINT "twitterpassage_id_refs_id_720f772f" FOREIGN KEY (twitterpassage_id) REFERENCES connectr_twitterpassage(id) DEFERRABLE INITIALLY DEFERRED


connectr=# \d connectr_twitterpassage_words
                               Table "public.connectr_twitterpassage_words"
      Column       |  Type   |                                 Modifiers                                  
-------------------+---------+----------------------------------------------------------------------------
 id                | integer | not null default nextval('connectr_twitterpassage_words_id_seq'::regclass)
 twitterpassage_id | integer | not null
 word_id           | integer | not null
Indexes:
    "connectr_twitterpassage_words_pkey" PRIMARY KEY, btree (id)
    "connectr_twitterpassage_twitterpassage_id_613c80271f09fba8_uniq" UNIQUE CONSTRAINT, btree (twitterpassage_id, word_id)
    "connectr_twitterpassage_words_twitterpassage_id" btree (twitterpassage_id)
    "connectr_twitterpassage_words_word_id" btree (word_id)
    "word_to_twitterpassage_id" btree (word_id, twitterpassage_id)
Foreign-key constraints:
    "twitterpassage_id_refs_id_720f772f" FOREIGN KEY (twitterpassage_id) REFERENCES connectr_twitterpassage(id) DEFERRABLE INITIALLY DEFERRED
    "word_id_refs_id_64f49629" FOREIGN KEY (word_id) REFERENCES connectr_word(id) DEFERRABLE INITIALLY DEFERRED

connectr=# \d connectr_word
                                        Table "public.connectr_word"
       Column        |           Type           |                         Modifiers                          
---------------------+--------------------------+------------------------------------------------------------
 id                  | integer                  | not null default nextval('connectr_word_id_seq'::regclass)
 word                | character varying(10000) | not null
 created             | timestamp with time zone | not null
 modified            | timestamp with time zone | not null
 frequency           | double precision         | 
 is_username         | boolean                  | not null
 is_hashtag          | boolean                  | not null
 cloud_eligible      | boolean                  | not null
 passage_count       | integer                  | 
 avg_quality         | double precision         | 
 last_twitter_search | timestamp with time zone | 
 cloud_approved      | boolean                  | not null
 display_word        | character varying(10000) | not null
 is_trend            | boolean                  | not null
Indexes:
    "connectr_word_pkey" PRIMARY KEY, btree (id)
    "connectr_word_word_uniq" UNIQUE CONSTRAINT, btree (word)
    "connectr_word_avg_quality" btree (avg_quality)
    "connectr_word_cloud_eligible" btree (cloud_eligible)
    "connectr_word_last_twitter_search" btree (last_twitter_search)
    "connectr_word_passage_count" btree (passage_count)
    "connectr_word_word" btree (word)
Referenced by:
    TABLE "connectr_passageviewevent" CONSTRAINT "source_word_id_refs_id_178d46eb" FOREIGN KEY (source_word_id) REFERENCES connectr_word(id) DEFERRABLE INITIALLY DEFERRED
    TABLE "connectr_wordmatchrewardevent" CONSTRAINT "tapped_word_id_refs_id_c2ffb369" FOREIGN KEY (tapped_word_id) REFERENCES connectr_word(id) DEFERRABLE INITIALLY DEFERRED
    TABLE "connectr_connection" CONSTRAINT "word_id_refs_id_00cccde2" FOREIGN KEY (word_id) REFERENCES connectr_word(id) DEFERRABLE INITIALLY DEFERRED
    TABLE "connectr_twitterpassage_words" CONSTRAINT "word_id_refs_id_64f49629" FOREIGN KEY (word_id) REFERENCES connectr_word(id) DEFERRABLE INITIALLY DEFERRED
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1 回答 1

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查看解释输出，排序所花费的时间很少。它正在收集需要进行排序的数据，这需要时间。

您必须花费一些时间来访问磁盘。如果您可以更好地缓存数据，那么使用相同的查询应该会大大加快速度。

否则，您最好的选择可能是通过将 quality 字段添加到 connectr_twitterpassage_words 表并在 (word_id, quality,...)

于 2013-10-11T18:17:24.463 回答