如何优化这个缓慢的 PostgreSQL 查询

Question

我已经跟踪到 SQL 查询的 API 端点速度慢的原因，但我终生无法对其进行优化。

查询如下：

SELECT "Views".*, "Show".*, "Episode".*, "User".* FROM "Views"
LEFT OUTER JOIN "Shows" AS "Show" ON "Show"."id" = "Views"."ShowId"
LEFT OUTER JOIN "Episodes" AS "Episode" ON "Episode"."id" = "Views"."EpisodeId"
LEFT OUTER JOIN "Users" AS "User" ON "User"."id" = "Views"."UserId"
WHERE "Show"."tvdb_id" IN (259063,82066,258823,265766,261742,82283,205281,182061,121361)
AND "User"."id"=29;

完成需要 3000-4200 毫秒。查询的 EXPLAIN ANALYZE 的结果可以在这里找到：http://explain.depesz.com/s/J9R

编辑：我也尝试将 IN() 分成 OR：

SELECT "Views".*, "Show".*, "Episode".*, "User".* FROM "Views"
LEFT OUTER JOIN "Shows" AS "Show" ON "Show"."id" = "Views"."ShowId"
LEFT OUTER JOIN "Episodes" AS "Episode" ON "Episode"."id" = "Views"."EpisodeId"
LEFT OUTER JOIN "Users" AS "User" ON "User"."id" = "Views"."UserId"
WHERE
    "Show"."tvdb_id"=259063 OR
    "Show"."tvdb_id"=82066 OR
    "Show"."tvdb_id"=258823 OR
    "Show"."tvdb_id"=265766 OR
    "Show"."tvdb_id"=261742 OR
    "Show"."tvdb_id"=82283 OR
    "Show"."tvdb_id"=205281 OR
    "Show"."tvdb_id"=182061 OR
    "Show"."tvdb_id"=121361 
AND "User"."id"=29; 

我曾尝试在LEFT OUTER JOIN 中引用的列上创建索引，但这导致了边际收益（如果有的话）。有趣的是，我还尝试将WHERE x IN 减少为单个WHERE x = y，这立即改善了情况，而是在 200-300 毫秒内响应。那么我该如何优化 IN 语句呢？

谢谢！

Answer 1

尝试对 ShowId、EpisodeId、UserId 字段的表 Views 进行组合索引。

CREATE INDEX Views_idx ON Views
  USING btree (ShowId, EpisodeId, UserId);

ps。解释链接错误，是为了其他查询

最好的问候，

内尔