ruby-on-rails-3 - PostgreSQL 查询在本地 (9.x) 工作，但在 Heroku (8.x) 上给出语法错误

Question

我开发了我的网站，它在我的本地机器上运行得非常好。查询由一位 Stackoverflow 成员提供 in this thread .

schema.rb portion that is relevant

本地数据与 Heroku 上的数据相同。

select  *
from    (
        select  *
        ,       row_number() over (partition by odds_type order by odds_index desc) as rn2
        from    (
                select  *
                ,       row_number() over (partition by event_id, bookmaker_id, odds_type 
                                           order by created_at desc) as rn1
                from    Odds
                where   event_id = #{e.id}
                ) sub1
        where   rn1 = 1
        ) sub2
where   rn2 = 1

控制台报错

Odds Load (88.4ms)  select * from ( select *, row_number() over (partition by odds_type order by odds_index desc) as rn2 from (select *, row_number() over (partition by event_id, bookmaker_id, odds_type order by created_at desc) as rn1 from Odds where event_id = 21 ) sub1 where rn1 = 1 ) sub2where rn2 = 1
ActiveRecord::StatementInvalid: PG::Error: ERROR:  syntax error at or near "over"
LINE 1: select * from ( select *, row_number() over (partition by od...
                                           ^

Answer 1

row_number() 和 window functions通常在 PostgreSQL 8.4 或更高版本中可用。该错误表明您正在旧版本(8.3？)上尝试此查询，因此它无法工作。

更新:在使用 PG 9.x 研究了原始问题和答案之后，我相信您可以使用 PostgreSQL 特定的 DISTINCT ON 获得相同的结果。子句，非标准但在旧版本的 PG 中可用，并且在您的情况下非常方便。这是我的建议:

SELECT DISTINCT on (ot) bi,ot,oi FROM
  (select distinct on (bi,ot) bi,ot,oi from odds
    where ei=1 order by bi,ot,created_at desc) subq
 ORDER BY ot,oi DESC;