Question

我目前正在尝试管理postgreSql数据库中数据集的修订。我想使用的表具有以下结构：

CREATE TABLE dataset (
   id BIGSERIAL PRIMARY KEY,
   revision INTEGER NOT NULL,
   object_id BIGINT NOT NULL
);

id字段是唯一的自动增量标识符。 object_id应该是对象的标识符，而revision会跟踪修订：

id | object_id | revision
-------------------------
 1 |         1 |        1
 2 |         2 |        1
 3 |         1 |        2
 4 |         1 |        3
 5 |         3 |        1
 6 |         4 |        1

我现在需要的是一个功能，即：

如果未提供object_id，则设置自动增量object_id并将版本设置为1.
如果提供了object_id，则为此object_id设置自动增量修订。

我已经找到了this answer，但这并没有真正解决为object_id创建连续修订的问题，也没有解决自动创建连续object_id的问题。

修改

我会做类似以下的事情，但这感觉不太舒服：

CREATE OR REPLACE FUNCTION update_revision() RETURNS TRIGGER LANGUAGE plpgsql AS
$$
BEGIN
    IF tg_op='INSERT' THEN
        IF NEW.object_id != NULL THEN
            NEW.object_id = SELECT nextval(object_id_seq_id);
            NEW.revision = 1;
        ELSE
            NEW.revision = SELECT MAX(revision)+1 FROM dataset WHERE spot_id = NEW.spot_id;
        END IF;
    END IF;

    RETURN NEW;
END;
$$;

CREATE TRIGGER update_revision BEFORE INSERT OR UPDATE ON dataset
    FOR EACH ROW EXECUTE PROCEDURE update_revision();

Answer 1

制作(object_id, revision) unique。 BTW为什么他们不是primary key？

create table dataset (
    id bigserial primary key,
    object_id bigint not null,
    revision integer not null,
    unique (object_id, revision)
);

create or replace function include_revision (_object_id integer)
returns dataset as $$
    with object_id as (
        select coalesce(max(object_id), 0) + 1 as object_id
        from dataset
    ), revision as (
        select coalesce(max(revision), 0) + 1 as revision
        from dataset
        where object_id = _object_id
    )
    insert into dataset (object_id, revision)
    select
        coalesce(_object_id, (select object_id from object_id)),
        (select revision from revision)
    returning *
    ;
$$ language sql;

object_id设置为coalesce(_object_id, (select object_id from object_id))，也就是说，只有当_object_id为空时才会使用计算出的max(object_id)

测试：

select include_revision(null);
 include_revision 
------------------
 (1,1,1)

select include_revision(1);
 include_revision 
------------------
 (2,1,2)

select include_revision(null);
 include_revision 
------------------
 (3,2,1)

管理postgresql中的修订

1 个答案: