PL/SQL Triggers with dynamic sql - oracle

Question

I want to create ddl trigger(on create) which will create a dml trigger
But i have error:
ORA-06512: на line 8
00604. 00000 - "error occurred at recursive SQL level %s"
*Cause: An error occurred while processing a recursive SQL statement
(a statement applying to internal dictionary tables).
*Action: If the situation described in the next error on the stack
can be corrected, do so; otherwise contact Oracle Support.
CREATE OR REPLACE TRIGGER test_ddl
after CREATE ON SCHEMA
DECLARE
user_col VARCHAR(5) := 'user_';
time_col VARCHAR(5) := 'time_';
BEGIN
IF ora_dict_obj_type = 'TABLE'
THEN
EXECUTE IMMEDIATE 'alter table ' || ora_dict_obj_name || ' add(' || user_col || ' varchar(20), '|| time_col ||' timestamp)'||'';
EXECUTE IMMEDIATE 'CREATE OR REPLACE TRIGGER add_user_time BEFORE INSERT OR UPDATE ON test_tab FOR EACH ROW BEGIN ' || ':' || 'new.time_ := sysdate; END';
END IF;
END;
/
DROP TABLE test_tab PURGE;
/
CREATE TABLE test_tab(ID NUMBER);

Answer 1

At the very least, I expect you want new.time_ to be :new.time_

Answer 2

You are missing a semicolon after the END.
Replace this
EXECUTE IMMEDIATE 'CREATE OR REPLACE TRIGGER add_user_time BEFORE INSERT OR UPDATE ON test_tab FOR EACH ROW BEGIN ' || ':' || 'new.time_ := sysdate; END';
with that
EXECUTE IMMEDIATE 'CREATE OR REPLACE TRIGGER add_user_time BEFORE INSERT OR UPDATE ON test_tab FOR EACH ROW BEGIN ' || ':' || 'new.time_ := sysdate; END;';
Full error messages are:
ORA-00604: error occurred at recursive SQL level 1
ORA-24344: success with compilation error
ORA-06512: at line 8
Important part was:
ORA-24344: success with compilation error
The source code should read:
CREATE OR REPLACE TRIGGER test_ddl
after CREATE ON SCHEMA
DECLARE
user_col VARCHAR(5) := 'user_';
time_col VARCHAR(5) := 'time_';
BEGIN
IF ora_dict_obj_type = 'TABLE'
THEN
EXECUTE IMMEDIATE 'alter table ' || ora_dict_obj_name || ' add(' || user_col || ' varchar(20), '|| time_col ||' timestamp)'||'';
EXECUTE IMMEDIATE 'CREATE OR REPLACE TRIGGER add_user_time BEFORE INSERT OR UPDATE ON test_tab FOR EACH ROW BEGIN ' || ':' || 'new.time_ := sysdate; END;';
END IF;
END;
/
DROP TABLE test_tab PURGE;
/
CREATE TABLE test_tab(ID NUMBER);
Just as an explanation: I have put some log messages to see where it exactly fails. Then you can see that the trigger is recursively called upon the CREATE OR REPLACE TRIGGER but with an ora_dict_obj_type = TRIGGER