postgresql - Postgres : Best way to query hierarchy structures by name

Question

假设我有一个类别层次结构，如下所示:

id |     name   | parent_id
---+------------+-----------
 1 | Computers  |  
---+------------+-----------
 2 | Laptops    | 1
---+------------+-----------
 3 | Desktops   | 1
---+------------+-----------
 4 | Big        | 2
---+------------+-----------
 5 | Small      | 2
 ---+------------+-----------
 4 | Big        | 3
---+------------+-----------
 5 | Small      | 3

现在，假设有人给我输入 ['Computers', 'Laptops', 'Small']。在 Postgres 中查询层次结构并到达正确的结束类别(例如 id 5)的最佳方法是什么？

我知道您可以使用递归 CTE 遍历树，但是将输入数组参数化到查询中的最佳方法是什么？

以下或多或少可行，但感觉真的低于标准，因为您必须拆分参数数组:

WITH RECURSIVE path(n, id, name, parent_id) AS (
  SELECT 
    1, c.id, c.name, c.parent_id
  FROM 
    categories c
  WHERE c.name = 'Computers' AND parent_id IS NULL
  UNION ALL
  SELECT n+1, c.id, c.name, c.parent_id 
  FROM categories c,
    (SELECT * FROM unnest(ARRAY['Laptops', 'Small']) WITH ORDINALITY np(name, m)) np,
    path p
    WHERE c.parent_id = p.id AND np.m = n AND np.name = c.name
)
SELECT * FROM path;

Answer 1

CTE 应如下所示:

WITH RECURSIVE search AS (
  SELECT ARRAY['Computers', 'Laptops', 'Small'] AS terms
), path (n, id, name, parent_id) AS (
  SELECT 1, id, name, parent_id
  FROM categories, search
  WHERE name = terms[1]
  UNION
  SELECT p.n+1, c.id, c.name, c.parent_id
  FROM categories c, path p, search s
  WHERE c.parent_id = p.id
    AND c.name = (s.terms)[p.n+1]
)
SELECT * FROM path;

巧妙的是，您只需指定一次数组，然后 CTE 的其他项就可以简单地遍历数组，无论路径有多长。不需要取消嵌套。请注意，这也适用于部分树:['Desktop', 'Big'] 将很好地生成正确的路径(显然不包括 'Computer')。

SQLFiddle here