与postgres的Sqlalchemy。尝试让“ DISTINCT ON”代替“ DISTINCT” [英] Sqlalchemy with postgres. Try to get 'DISTINCT ON' instead of 'DISTINCT'

问题描述

我需要生成这样的查询：

I need to generate query like this:

SELECT **DISTINCT ON** (article.code) article.code, article.title

首先，我尝试通过ORM独特的方法进行创建，并向其发送包含字段的列表。但它不会工作。其次，我尝试通过sqlalchemy.sql.select进行创建-并且还会生成如下这样的sql查询：

First I try to make it via ORM distinct method and send it a list with fields. But it wont work. Second, I try to make it via sqlalchemy.sql.select - and it also generate sql query like this:

SELECT DISTINCT article.code, article.title

我需要 SELECT ** DISTINCT ON ** （文章代码） ...

我查看源代码并在 sqlalchemy.dialects.postgresql中找到。 base.PGCompiler.get_select_precolumns 代码，用于生成以下结构：'DISTINCT ON'
但是未调用此方法。代替此方法的是另一种方法- sqlalchemy.sql.compiler.get_select_precolumns -它没有用于生成 DISTINCT ON 的代码仅用于 DISTINCT 也许我应该将会话配置为正确调用的方法？

I look at source code and found in sqlalchemy.dialects.postgresql.base.PGCompiler.get_select_precolumns code for generating constructions like: 'DISTINCT ON' But this method do not called. Instead of this called another method - sqlalchemy.sql.compiler.get_select_precolumns - it hasn't code for generating DISTINCT ON only for DISTINCT Maybe I should configure my session to called properly method?

推荐答案

此错误报告表明 DISTINCT ON 在SQLAlchemy 0.7+中可以正常工作。我认为升级是有序的，除非您发现0.7中的错误。

This bug report suggests that DISTINCT ON works correctly in SQLAlchemy 0.7+. I think an upgrade is in order, unless you've uncovered a bug in 0.7.

解决方法。 。

• 志愿者帮助为Ubuntu准备好0.7软件包
  。


• < a href = http://www.sqlalchemy.org/download.html rel = nofollow>下载并从
  源安装。


• 重写避免 DISTINCT
ON 的查询。我不确定在最一般的情况下是否有可能
  。

• Volunteer to help get the 0.7 package ready for Ubuntu.
• Download and install from source.
• Rewrite queries to avoid DISTINCT ON. I'm not sure whether that's possible in the most general case.

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