sql - 编写 PostgreSQl 函数的更好方法

Question

这是我从 MS SQLServer 转换到 PostgreSQL 的存储过程。有没有更好的方法在 Postgres 中编写它。还有什么应该是最佳实践？任何帮助将不胜感激。

create or replace function GenSerialNo_SP1(tname character varying) returns AS $$

--declare @PK bigint
declare totalRec bigint;
declare getRec bigint;
Begin

    --set @PK = 1
    set totalRec=-1;

    for getRec inselect coalesce(primary_key,0) from STD_SERIAL_NOS 
   where table_name = tname
    loop
    open  getRec;
    fetch next from getRec into totalRec;
    close getRec;
    deallocate getRec;
    end loop;
    if totalRec = -1 then

        insert into STD_SERIAL_NOS (TABLE_NAME, PRIMARY_KEY) values (tname, 1);

    else

        update STD_SERIAL_NOS set primary_key = primary_key +1 
           where table_name = tname;

    end if;

end;
$$ language plpgsql;

Answer 1

它看起来像一个 UPSERT ，但您不需要任何游标即可实现。

假设 STD_SERIAL_NOS.table_name 上有一个唯一索引，一个(希望如此)正确的版本(包括处理插入时的竞争条件)将是:

create or replace function GenSerialNo_SP1(tname character varying) returns void
as $$
begin
  loop
   begin
     update STD_SERIAL_NOS set primary_key = primary_key +1 
        where table_name = tname;
     exit when found; -- exit loop if the row exists, otherwise insert it
     insert into STD_SERIAL_NOS (TABLE_NAME, PRIMARY_KEY)
        values(tname,1);
   exception  WHEN unique_violation THEN
     -- the insert conflicts, let's go back to the update in the next loop iteration
   end;
  end loop;

end;
$$ language plpgsql;