Postgres級聯刪除與觸發器

Question

我有以下數據庫結構：

table a (
    id     bigint primary key,
    del    timestamp
);
table b (
    id     bigint primary key,
    a_id   bigint references a(id) on delete cascade,
    del    timestamp
);

從表a刪除記錄時，我想在當前時間設置del標志，並將表b的相應標志用小寫（但實際上不從數據庫中刪除記錄）。

為此，我編寫了一個觸發器：

create or replace function a_delete_trigger()
    returns trigger as
$$
begin
    update a
    set del = now()
    where id = old.id; -- mark row

    return null; -- return null, so that the record is not removed from database
end;
$$
language plpgsql;
create trigger a_delete
    before delete
    on a
    for each row
execute procedure a_delete_trigger();

和表b的觸發器：

create or replace function b_delete_trigger()
    returns trigger as
$$
begin
    update b
    set del = now()
    where id = old.id;

    return null;
end;
$$
language plpgsql;
create trigger b_delete
    before delete
    on b
    for each row
execute procedure b_delete_trigger();

當我從表a刪除一條記錄（ delete from a where id = ? ）時，該記錄被標記為已刪除（標志del包含時間戳記），但是未標記表b中的適當記錄（我猜這是級聯刪除）不起作用，因為我從觸發器a_delete_trigger返回null）

我該如何做，當我從表a刪除一條記錄時，該記錄標記為已刪除，而b相應記錄也將標記為已刪除？

Answer 1

將刪除b添加到a_delete_trigger。

create or replace function a_delete_trigger()
    returns trigger as
$$
begin
    update a
    set del = now()
    where id = old.id; -- mark row

    delete from b where a_id = a.id;

    return null; -- return null, so that the record is not removed from database
end;
$$
language plpgsql;
create trigger a_delete
    before delete
    on a
    for each row
execute procedure a_delete_trigger();