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Postgres级联删除与触发器

[英]Postgres cascade delete with trigger

我有以下数据库结构:

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
);

从表a删除记录时,我想在当前时间设置del标志,并将表b的相应标志用小写(但实际上不从数据库中删除记录)。

为此,我编写了一个触发器:

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的触发器:

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();

当我从表a删除一条记录( delete from a where id = ? )时,该记录被标记为已删除(标志del包含时间戳记),但是未标记表b中的适当记录(我猜这是级联删除)不起作用,因为我从触发器a_delete_trigger返回null)

我该如何做,当我从表a删除一条记录时,该记录标记为已删除,而b相应记录也将标记为已删除?

将删除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();

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