如何在 PostgreSQL 中对递归查询进行排序

Question

我有 sql 查询来查找来自原始评论的所有回复：

WITH RECURSIVE children AS (
        SELECT blog_comments_comment.*, 0 AS relative_depth
        FROM blog_comments_comment
        WHERE id in %s

        UNION ALL

        SELECT blog_comments_comment.*, children.relative_depth + 1
        FROM blog_comments_comment,children
        WHERE blog_comments_comment.reply_to_id = children.id
    )
    SELECT id,post_id, name,body, reply_to_id, relative_depth
    FROM children
    ORDER BY children;

我怎样才能对它进行排序以使其成为这样？

-main comment
---reply to main comment
------reply to reply
----------etc
---2nd reply to main comment
------reply to 2nd reply
----------etc

Answer 1

维护路径并排序：

WITH RECURSIVE children AS (
        SELECT bcc.*, 0 AS relative_depth,
               array[bcc.id] as path
        FROM blog_comments_comment bcc
        WHERE id in %s    
        UNION ALL    
        SELECT bcc.*, c.relative_depth + 1,
               path || c.id
        FROM children c JOIN
             blog_comments_comment bcc
             ON bcc.reply_to_id = bcc.id
    )
SELECT id,post_id, name,body, reply_to_id, relative_depth
FROM children
ORDER BY path;

这是一个 db<>fiddle。