KingbaseES 如何实现Oracle pipelined 功能

管道函数即是可以返回行集合（可以使嵌套表nested table 或数组 varray）的函数，我们可以像查询物理表一样查询它或者将其赋值给集合变量。KingbaseES 数据库可以用 setof 实现类似 Oracle 的pipelined 功能，C5版本开始，也支持pipeline。

一、Oracle pipelined 使用例子

create or replace type varchar_type as table of varchar(100);

create or replace function func_pipeline_test return varchar_type
pipelined as
begin
  for i in 1..5 loop
    pipe row('Pipeline '||i||' '||systimestamp);
    dbms_lock.sleep(1);
  end loop;
  return;
end;
/

SQL> select * from table(func_pipeline_test);

COLUMN_VALUE
--------------------------------------------------------------------------------
Pipeline 1 01-JUL-21 07.22.21.630651000 PM +08:00
Pipeline 2 01-JUL-21 07.22.22.630975000 PM +08:00
Pipeline 3 01-JUL-21 07.22.23.631054000 PM +08:00
Pipeline 4 01-JUL-21 07.22.24.631381000 PM +08:00
Pipeline 5 01-JUL-21 07.22.25.631216000 PM +08:00

二、KingbaseES

1、pipelined

从V8R6C5 开始，KingbaseES 支持 pipeline，其使用与 Oracle 完全相同。

create or replace type varchar_type as table of varchar(100);

create or replace function func_pipeline_test return varchar_type
pipelined as
begin
  for i in 1..5 loop
    pipe row('Pipeline '||i||' '||systimestamp);
    perform pg_sleep(1);
  end loop;
  return;
end;
/

test=# select * from table(func_pipeline_test());
               column_value
------------------------------------------
 Pipeline 1 2021-12-22 15:26:45.572780+08
 Pipeline 2 2021-12-22 15:26:45.572780+08
 Pipeline 3 2021-12-22 15:26:45.572780+08
 Pipeline 4 2021-12-22 15:26:45.572780+08
 Pipeline 5 2021-12-22 15:26:45.572780+08
(5 rows)

2、setof 使用例子

create or replace function func_pipeline_test1 returns setof text as
declare
  v_text text;
begin
  for i in 1..5 loop
    return query select 'Pipeline '||i||' '||clock_timestamp() ;
    perform sys_sleep(1);
  end loop;
  return;
end
/

test=# select func_pipeline_test1();
           func_pipeline_test1
------------------------------------------
Pipeline 1 2021-09-13 17:36:55.571164+08
Pipeline 2 2021-09-13 17:36:56.572743+08
Pipeline 3 2021-09-13 17:36:57.574097+08
Pipeline 4 2021-09-13 17:36:58.575511+08
Pipeline 5 2021-09-13 17:36:59.577169+08

(5 rows)

create or replace function func_pipeline_test2 returns setof t1 as
declare
  v_t1 t1%rowtype;
begin
  for v_t1 in (select * from t1) loop
    return next v_t1;
  end loop;
  return;
end
/

test=# select * from func_pipeline_test2();
id | name
----+------
1 | abc
2 | abc
3 | abc
4 | abc
5 | abc
6 | abc
7 | abc
8 | abc
9 | abc
10 | abc
(10 rows)

3、table function

create or replace type int_set as table of integer;

create or replace function func1() return int_set as
  v_temp int_set := int_set(1,2,3);
begin
  return v_temp;
end;

test=# select func1();
     func1
----------------
 int_set(1,2,3)
(1 row)

test=# select * from table(func1());
 column_value
--------------
            1
            2
            3