PostgreSQL复制树表中的数据 [英] Postgresql copy data within the tree table

问题描述

我的表具有树结构，列为 id ，类别， parent_id

I have table with tree structure, columns are id, category, parent_id

现在我需要将一个节点及其子节点复制到另一个节点，在复制时，类别必须相同，但是具有新的id和parent_id.

Now I need a copy a node and its child's to a another node, while copying, the category must be same, but with new id and parent_id..

我的输入将是要复制的节点&要复制的目标节点

My input will be node to copy & destination node to copy

我已经解释了图像文件中的树结构.

I have explained the tree structure in the image file..

我需要一个函数来做..，

i need a function to do so..,

PostgreSQL版本9.1.2

  Column   |  Type   |                    Modifiers                    
-----------+---------+-------------------------------------------------
 id        | integer | not null default nextval('t1_id_seq'::regclass)
 category  | text    | 
 parent_id | integer | 
Indexes:
    "t1_pkey" PRIMARY KEY, btree (id)
Foreign-key constraints:
    "fk_t1_1" FOREIGN KEY (parent_id) REFERENCES t1(id)
Referenced by:
    TABLE "t1" CONSTRAINT "fk_t1_1" FOREIGN KEY (parent_id) REFERENCES t1(id)

推荐答案

(在PostgreSQL 8.4.3下测试)

以下查询将新ID分配给节点4下的子树(请参见 nextval )，然后找到相应的新父母父母的ID(请参见左键).

The following query assigns new IDs to the sub-tree under node 4 (see the nextval) and then finds the corresponding new IDs of parents (see the LEFT JOIN).

WITH RECURSIVE CTE AS (
    SELECT *, nextval('t1_id_seq') new_id FROM t1 WHERE id = 4
    UNION ALL
    SELECT t1.*, nextval('t1_id_seq') new_id FROM CTE JOIN t1 ON CTE.id = t1.parent_id
)
SELECT C1.new_id, C1.category, C2.new_id new_parent_id
FROM CTE C1 LEFT JOIN CTE C2 ON C1.parent_id = C2.id

结果(关于您的测试数据):

Result (on your test data):

new_id  category    new_parent_id
------  --------    -------------
9       C4          
10      C5          9
11      C6          9
12      C7          10

一旦有了它，就很容易将其插入到表中，只需小心地将子树根与适当的父级重新连接(在这种情况下为8，请参见 COALESCE(new_parent_id，8)):

Once you have that, it's easy to insert it back to the table, you just have to be careful to reconnect the sub-tree root with the appropriate parent (8 in this case, see the COALESCE(new_parent_id, 8)):

INSERT INTO t1
SELECT new_id, category, COALESCE(new_parent_id, 8) FROM (
    WITH RECURSIVE CTE AS (
        SELECT *, nextval('t1_id_seq') new_id FROM t1 WHERE id = 4
        UNION ALL
        SELECT t1.*, nextval('t1_id_seq') new_id FROM CTE JOIN t1 ON CTE.id = t1.parent_id
    )
    SELECT C1.new_id, C1.category, C2.new_id new_parent_id
    FROM CTE C1 LEFT JOIN CTE C2 ON C1.parent_id = C2.id
) Q1

此后，该表包含以下数据:

After that, the table contains the following data:

new_id  category    new_parent_id
------  --------    -------------
1       C1
2       C2          1
3       C3          1
4       C4          2
5       C5          4
6       C6          4
7       C7          5
8       C8          3
9       C4          8
10      C5          9
11      C6          9
12      C7          10

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