racle的PL/SQL提供了Pipelined Table Functions特性用于把多行数据返回到调用者，可以有效的提升性能。
在PostgreSQL中，可以通过在函数中利用SETOF或者RETURN NEXT来实现。
Oracle
创建数据表，插入数据
TEST-orcl@DESKTOP-V430TU3>drop table t_piperow;drop table t_piperow *ERROR at line 1:ORA-00942: table or view does not existTEST-orcl@DESKTOP-V430TU3>create table t_piperow(id int,c1 timestamp ,c2 varchar2(20),c3 number);Table created.TEST-orcl@DESKTOP-V430TU3>TEST-orcl@DESKTOP-V430TU3>insert into t_piperow(id,c1,c2,c3) 2 select rownum,sysdate,'test'||rownum,123455.55 from dba_objects where rownum <= 500;500 rows created.TEST-orcl@DESKTOP-V430TU3>commit;Commit complete.TEST-orcl@DESKTOP-V430TU3>创建Type
TEST-orcl@DESKTOP-V430TU3>CREATE OR REPLACE TYPE rec_t_piperow AS OBJECT(id int,c1 timestamp ,c2 varchar2(20),c3 number); 2 /Type created.TEST-orcl@DESKTOP-V430TU3>CREATE OR REPLACE TYPE type_t_piperow AS TABLE OF rec_t_piperow; 2 /Type created.函数实现
TEST-orcl@DESKTOP-V430TU3>CREATE OR REPLACE FUNCTION func_piperow_demo1 RETURN type_t_piperow PIPELINED IS 2 BEGIN 3 FOR rec in (select * from t_piperow) LOOP 4 PIPE ROW (rec_t_piperow(rec.id,rec.c1,rec.c2,rec.c3)); 5 END LOOP; 6 RETURN; 7 END; 8 /Function created.查询数据
TEST-orcl@DESKTOP-V430TU3>column c3 format 9999999999999.9999TEST-orcl@DESKTOP-V430TU3>select * from table(func_piperow_demo1()) where rownum < 5; ID C1 C2 C3---------- -------------------- -------------------- ------------------- 1 31-OCT-19 10.50.38.0 test1 123455.5500 00000 AM 2 31-OCT-19 10.50.38.0 test2 123455.5500 00000 AM 3 31-OCT-19 10.50.38.0 test3 123455.5500 00000 AM 4 31-OCT-19 10.50.38.0 test4 123455.5500 00000 AMPostgreSQL
下面来看看PG的实现，创建表，插入数据
[local]:5432 pg12@testdb=# drop table if exists t_piperow;DROP TABLETime: 5.255 ms[local]:5432 pg12@testdb=# create table t_piperow(id int,c1 timestamp ,c2 varchar(20),c3 float);CREATE TABLETime: 4.711 ms[local]:5432 pg12@testdb=# [local]:5432 pg12@testdb=# insert into t_piperow(id,c1,c2,c3) pg12@testdb-# select x,now(),'test'||x,123455.55 from generate_series(1,500) x;INSERT 0 500Time: 10.183 ms[local]:5432 pg12@testdb=# [local]:5432 pg12@testdb=#函数实现
第一种方式，使用SQL：
[local]:5432 pg12@testdb=# CREATE OR REPLACE FUNCTION func_piperow_demo1() RETURNS SETOF PUBLIC.t_piperowpg12@testdb-# ASpg12@testdb-# $$pg12@testdb$# SELECT * FROM t_piperow;pg12@testdb$# $$pg12@testdb-# LANGUAGE SQL;CREATE FUNCTIONTime: 1.341 ms[local]:5432 pg12@testdb=# [local]:5432 pg12@testdb=# select func_piperow_demo1() limit 5; func_piperow_demo1 -------------------------------------------------- (1,"2019-10-31 11:09:27.222996",test1,123455.55) (2,"2019-10-31 11:09:27.222996",test2,123455.55) (3,"2019-10-31 11:09:27.222996",test3,123455.55) (4,"2019-10-31 11:09:27.222996",test4,123455.55) (5,"2019-10-31 11:09:27.222996",test5,123455.55)(5 rows)Time: 1.038 ms[local]:5432 pg12@testdb=#第二种方式，使用PL/pgSQL，RETURN QUERY
[local]:5432 pg12@testdb=# CREATE OR REPLACE FUNCTION func_piperow_demo2() RETURNS SETOF PUBLIC.t_piperowpg12@testdb-# ASpg12@testdb-# $$pg12@testdb$# BEGINpg12@testdb$# RETURN QUERY SELECT * FROM t_piperow;pg12@testdb$# END;pg12@testdb$# $$pg12@testdb-# LANGUAGE PLPGSQL;CREATE FUNCTIONTime: 3.850 ms[local]:5432 pg12@testdb=# select func_piperow_demo2() limit 5; func_piperow_demo2 -------------------------------------------------- (1,"2019-10-31 11:09:27.222996",test1,123455.55) (2,"2019-10-31 11:09:27.222996",test2,123455.55) (3,"2019-10-31 11:09:27.222996",test3,123455.55) (4,"2019-10-31 11:09:27.222996",test4,123455.55) (5,"2019-10-31 11:09:27.222996",test5,123455.55)(5 rows)Time: 5.645 ms[local]:5432 pg12@testdb=#第三种方式，使用PL/pgSQL，RETURN NEXT
[local]:5432 pg12@testdb=# select func_piperow_demo3() limit 5; func_piperow_demo3 -------------------------------------------------- (1,"2019-10-31 11:09:27.222996",test1,123455.55) (2,"2019-10-31 11:09:27.222996",test2,123455.55) (3,"2019-10-31 11:09:27.222996",test3,123455.55) (4,"2019-10-31 11:09:27.222996",test4,123455.55) (5,"2019-10-31 11:09:27.222996",test5,123455.55)(5 rows)Time: 5.588 ms[local]:5432 pg12@testdb=#
