解决方案

Question

我的PostgreSQL users数据库中有9.3.6个表，有两列：id和another_id。 id是主键，another_id只是另一个具有唯一约束的整数列。

还有其他表按主键引用用户。

这是users表格描述：

Table "public.users"
        Column        |              Type              |               Modifiers                | Storage | Stats target | Description 
----------------------+--------------------------------+----------------------------------------+---------+--------------+-------------
 id                   | integer                        | not null                               | plain   |              | 
 another_id           | integer                        | not null                               | plain   |              | 

Indexes:
    "users_pkey" PRIMARY KEY, btree (id)
    "uniq_1483a5e93414710b" UNIQUE, btree (another_id)

Referenced by:
    TABLE "foo_table" CONSTRAINT "fk_4affc6e5a76ed395" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
    TABLE "bar_table" CONSTRAINT "fk_72936b1da76ed395" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
    TABLE "baz_table" CONSTRAINT "fk_83adbaf0a76ed395" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE

以下是foo_table说明：

Table "public.foo_table"
    Column    |              Type              |                   Modifiers                   | Storage  | Stats target | Description 
--------------+--------------------------------+-----------------------------------------------+----------+--------------+-------------
 id           | integer                        | not null                                      | plain    |              | 
 user_id      | integer                        |                                               | plain    |              | 

Indexes:
    "foo_table_pkey" PRIMARY KEY, btree (id)
    "idx_e52ffdeea76ed395" btree (user_id)
Foreign-key constraints:
    "fk_e52ffdeea76ed395" FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE

如何将PostgreSQL表中的主键从id列替换为another_id列并保持数据完整性？

Answer 1

我花了一些时间，最后想出了一个有效的解决方案。

我将在此发布以供将来参考。

解决方案

首先，您有三个表（foo_table，bar_table，baz_table），它们通过外键指向您的users表（称为{{ 1}}在所有情况下）。您需要将user_id到id中存储的ID替换为another_id。以下是如何做到的：

-- We are dropping the foreign key constraint on dependant table (in other case it will prevent us from updating the values)
ALTER TABLE foo_table DROP CONSTRAINT fk_e52ffdeea76ed395;

-- Then, we're swapping values in foreign key column from id to another_id
UPDATE foo_table T SET user_id = (SELECT another_id FROM users WHERE id = T.user_id);

-- And finally we're creating new foreign key constraint pointing to the another_id instead of id
ALTER TABLE foo_table ADD CONSTRAINT fk_e52ffdeea76ed395 FOREIGN KEY (user_id) REFERENCES users (another_id) ON DELETE CASCADE;

您需要为每个从属表重复上述查询。

之后，所有相关表格都会指向您的新another_id列。

最后我们只需要替换主键：

-- 1. Dropping the original primary key
ALTER TABLE users DROP CONSTRAINT users_pkey

-- 2. Renaming existing index for another_id (optional)
ALTER INDEX uniq_1483a5e93414710b RENAME TO users_pkey

-- 3. Creating new primary key using existing index for another_id
ALTER TABLE users ADD PRIMARY KEY USING INDEX users_pkey

-- 4. Creating index for old id column (optional)
CREATE UNIQUE INDEX users_id ON users (id)

-- 5. You can drop the original sequence generator if you won't need it
DROP SEQUENCE users_id_seq

如果您愿意，甚至可以删除原始id列。

我希望它会帮助别人。

更改PostgreSQL表中的主键

1 个答案:

解决方案