请问一个错误：ORA-03113: 通信通道的文件结束

CREATE OR REPLACE TYPE test_obj AS OBJECT(  c1 NUMBER,  c2 number);CREATE OR REPLACE TYPE test_type AS TABLE OF test_obj;--创建一个函数CREATE OR REPLACE FUNCTION testFuncRETURN test_type PIPELINEDASbegin    PIPE ROW(test_obj(1,2));      PIPE ROW(test_obj(3,4));    end;--测试该函数select * from table(testFunc());--创建一个表create table test_table(col_1 number);insert into test_table(col_1) values(1);insert into test_table(col_1) values(2);insert into test_table(col_1) values(3);--连接查询  ---------通过select * from test_table a,table(testFunc())b where a.col_1<=b.c1;----------下面这句查询报错"ORA-03113: 通信通道的文件结束"，并且把test_table清空--select * from test_table a,table(testFunc())b where a.col_1>=b.c1;