database - 依赖跟踪功能

Question

我只是想知道是否有人知道如何在运行后自动创建视图DROP ... CASCADE？现在我首先尝试使用经典DROP VIEW myview语句删除视图，如果我无法删除视图，因为其他对象仍然依赖它，然后检查 postgres 列出的所有对象名称并保存它们的创建，然后我使用级联运行 drop。有时它就像十几个物体。但也许你有一些想法以更自动化的方式处理这个问题？

也许有人有一些功能？

Answer 1

Next step... (continuation of my previous answer).

function save_views(objectname text) stores views depending on objectname (view or table) in table saved_views.

function restore_views() restores views from table saved_views.

create or replace function save_views_oid(objectid oid)
returns void language plpgsql as $$
declare
    r record;
begin
    for r in
        select distinct c.oid, c.relname, n.nspname
        from pg_depend d
        join pg_rewrite w on w.oid = d.objid
        join pg_class c on c.oid = w.ev_class
        join pg_namespace n on n.oid = c.relnamespace
        where d.refclassid = 'pg_class'::regclass 
        and d.classid = 'pg_rewrite'::regclass
        and d.refobjid = objectid
        and c.oid <> objectid
    loop
        insert into saved_views values (
            'CREATE VIEW ' || r.nspname || '.' || r.relname ||
            ' AS ' || pg_get_viewdef(r.oid, 'f'));
        perform save_views_oid(r.oid);
    end loop;
end; $$;

create or replace function save_views(objectname text)
returns void language plpgsql as $$
begin
    create table if not exists saved_views(viewbody text);
    truncate saved_views;
    perform save_views_oid(objectname::regclass);
end; $$;

create or replace function restore_views()
returns void language plpgsql as $$
declare
    viewtext text;
begin
    for viewtext in
        select viewbody from saved_views
    loop
        execute viewtext;
    end loop;
    drop table saved_views;
end; $$;

Test:

select save_views('my_view'); -- may be save_views('my_schema.my_view');
select * from saved_views;

Use:

select save_views('my_view'); 
drop view my_view cascade;
create view my_view as ...
select restore_views();

Answer 2

表pg_depend包含所有必要的信息，但解释它们并不容易。在这里，您有草图递归函数来检索文本格式的 pg_class 对象的依赖关系。您可以根据需要调整功能（并向我们展示结果：）。

create or replace function dependency
    (class_id regclass, obj_id regclass, obj_subid integer, dep_type "char")
returns setof text language plpgsql as $$
declare
    r record;
begin
    return query 
        select pg_describe_object(class_id, obj_id, obj_subid)
            || ' ('|| dep_type|| ')';
    for r in
        select classid, objid, objsubid, deptype
        from pg_depend
        where class_id = refclassid
        and obj_id = refobjid
        and (obj_subid = refobjsubid or obj_subid = 0)
    loop
        return query select dependency(r.classid, r.objid, r.objsubid, r.deptype);
    end loop;
end; $$;

use:

select dependency('pg_class'::regclass, 'my_view'::regclass, 0, ' ');
select dependency('pg_class'::regclass, 'my_table'::regclass, 0, ' ');