如何列出受级联删除影响的表

Question

我正在尝试对 15 个以上的表执行级联删除，但我不确定是否已正确配置所有必需的外键。我想在不手动检查每个约束的情况下检查是否缺少约束。

有没有办法获取将受级联删除查询影响的表的列表？

Answer 1

是的。您可以截断事务和回滚中的级联。注意 ROLLBACK 是保存数据的关键。 postgres 将 NOTICE 您将影响哪些其他引用表。

postgres=# begin;
BEGIN
postgres=# truncate table a cascade;
NOTICE:  truncate cascades to table "b"
TRUNCATE TABLE
postgres=# rollback;
ROLLBACK

Answer 2

使用pg_depend。示例：

create table master (id int primary key);
create table detail_1 (id int, master_id int references master(id) on delete restrict);
create table detail_2 (id int, master_id int references master(id) on delete cascade);

select pg_describe_object(classid, objid, objsubid)
from pg_depend 
where refobjid = 'master'::regclass and deptype = 'n';

                  pg_describe_object
------------------------------------------------------
 constraint detail_1_master_id_fkey on table detail_1
 constraint detail_2_master_id_fkey on table detail_2
(2 rows)

deptype = 'n' 表示：

DEPENDENCY NORMAL - A normal relationship between separately-created objects. The dependent object can be dropped without affecting the referenced object. The referenced object can only be dropped by specifying CASCADE, in which case the dependent object is dropped, too.

使用pg_get_constraintdef()获取约束定义：

select 
    pg_describe_object(classid, objid, objsubid), 
    pg_get_constraintdef(objid)
from pg_depend 
where refobjid = 'master'::regclass and deptype = 'n';


                  pg_describe_object                  |                       pg_get_constraintdef
------------------------------------------------------+------------------------------------------------------------------
 constraint detail_1_master_id_fkey on table detail_1 | FOREIGN KEY (master_id) REFERENCES master(id) ON DELETE RESTRICT
 constraint detail_2_master_id_fkey on table detail_2 | FOREIGN KEY (master_id) REFERENCES master(id) ON DELETE CASCADE
(2 rows)

要找到完整的级联依赖链，我们应该使用递归并查看目录 pg_constraint 以获得依赖 table.

的 id

with recursive chain as (
    select classid, objid, objsubid, conrelid
    from pg_depend d
    join pg_constraint c on c.oid = objid
    where refobjid = 'the_table'::regclass and deptype = 'n'
union all
    select d.classid, d.objid, d.objsubid, c.conrelid
    from pg_depend d
    join pg_constraint c on c.oid = objid
    join chain on d.refobjid = chain.conrelid and d.deptype = 'n'
    )
select pg_describe_object(classid, objid, objsubid), pg_get_constraintdef(objid)
from chain;

Answer 3

使用传递闭包，可以确定引用和被引用的 table。需要注意的是，这 query/view 依赖于外键的存在来确定依赖关系，并且不会如果 FK 丢失（并且后者似乎是 OP 所要求的）。

Table 通过外键的依赖关系

CREATE OR REPLACE VIEW table_dependencies AS (
WITH RECURSIVE t AS (
    SELECT
        c.oid AS origin_id,
        c.oid::regclass::text AS origin_table,
        c.oid AS referencing_id,
        c.oid::regclass::text AS referencing_table,
        c2.oid AS referenced_id,
        c2.oid::regclass::text AS referenced_table,
        ARRAY[c.oid::regclass,c2.oid::regclass] AS chain
    FROM pg_catalog.pg_constraint AS co
    INNER JOIN pg_catalog.pg_class AS c ON c.oid = co.conrelid
    INNER JOIN pg_catalog.pg_class AS c2 ON c2.oid = co.confrelid
--     Add this line as an input parameter if you want to make a one-off query
--     WHERE c.oid::regclass::text = 'YOUR TABLE'
    UNION ALL
    SELECT
        t.origin_id,
        t.origin_table,
        t.referenced_id AS referencing_id,
        t.referenced_table AS referencing_table,
        c3.oid AS referenced_id,
        c3.oid::regclass::text AS referenced_table,
        t.chain || c3.oid::regclass AS chain
    FROM pg_catalog.pg_constraint AS co
    INNER JOIN pg_catalog.pg_class AS c3 ON c3.oid = co.confrelid
    INNER JOIN t ON t.referenced_id = co.conrelid
    WHERE
        -- prevent infinite recursion by pruning paths where the last entry in
        -- the path already appears somewhere else in the path
        NOT (
            ARRAY[ t.chain[array_upper(t.chain, 1)] ] -- an array containing the last element
            <@                                        -- "is contained by"
            t.chain[1:array_upper(t.chain, 1) - 1]    -- a slice of the chain,
                                                      -- from element 1 to n-1
        )
)
SELECT  origin_table,
        referenced_table,
        array_upper(chain,1) AS "depth",
        array_to_string(chain,',') as chain
FROM t
);

Tables 引用特定的 table

SELECT * FROM table_dependencies WHERE origin_table = 'clients';

Table与"clients"table

直接相关

SELECT *
FROM table_dependencies
WHERE referenced_table = 'clients'
AND depth = 2
ORDER BY origin_table;

如何列出受级联删除影响的表

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Table 通过外键的依赖关系

Tables 引用特定的 table

Table与"clients"table