A unhandled exception in a "after create" trigger preventing create - oracle

Question

I have an AFTER CREATE trigger on my schema that raises an exception; I'm trying to create a table. I understand that an unhandled exception could cause the query/operation/transaction (I couldn't find suitable word for this case) to terminate. But, when the exception is raised after creating the table, shouldn't the table already be created by then?
When creating a table after successful triggering it throws error an error:
create table test(testcol number);
Error:
SQL Error: ORA-00604: error occurred at recursive SQL level 1
ORA-06510: PL/SQL: unhandled user-defined exception
ORA-06512: at line 4
Trigger:
create or replace trigger ddl_trig_2812
after create
on schema
declare
eirit exception;
begin
raise eirit;
end;
/

Answer 1

From the documentation:
In most cases, if a trigger runs a statement that raises an exception, and the exception is not handled by an exception handler, then the database rolls back the effects of both the trigger and its triggering statement.
It doesn't just cause it to terminate, as your question suggests. Your unhandled exception is causing the triggering statement - i.e. the create table - to be rolled back. When talking about DDL statements:
An implicit COMMIT occurs immediately before the database executes a DDL statement and a COMMIT or ROLLBACK occurs immediately afterward. In the preceding example, ... [if] the ALTER TABLE statement succeeds, then the database commits this statement; otherwise, the database rolls back this statement. ...
So this is expected behaviour.

Answer 2

The transaction begins with CREATE TABLE; then the AFTER CREATE trigger fires and raises an exception, i.e. table definition isn't "committed" into data dictionary tables (such as USER_TABLES, USER_TAB_COLUMNS, ...) but "rolled-back".
So - no, CREATE TABLE process hasn't been finished properly and you can't use that table as it isn't created because its creation was prevented by a trigger.

Answer 3

One good illustration to verify this would be to check if the table actually exists within the trigger.
Lets say you RAISE from the EXCEPTION block and query DBA_OBJECTS to see if object exists.
SQL> create or replace trigger ddl_trig_2812
2 after create
3 on schema
4 declare
5 v_table_name DBA_OBJECTS.OBJECT_NAME%TYPE;
6 eirit exception;
7 begin
8 select object_name into v_table_name from DBA_OBJECTS where object_name = 'ATEST';
9 raise eirit;
10 EXCEPTION
11 WHEN OTHERS THEN
12 DBMS_OUTPUT.PUT_LINE( 'TABLE CREATED '|| v_table_name );
13 RAISE;
14 END;
15
16 /
Trigger created.
Now, Lets create the table.
SQL> set serveroutput on;
SQL> create table atest ( a number);
TABLE CREATED ATEST
create table atest ( a number)
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-06510: PL/SQL: unhandled user-defined exception
ORA-06512: at line 10
Although exception was raised, the table exists in the data dictionary as you can see above the message displayed from dbms_output.
Now, if we check whether the table exists,
SQL> select * from atest;
select * from atest
*
ERROR at line 1:
ORA-00942: table or view does not exist
SQL> select object_name from DBA_OBJECTS where object_name = 'ATEST'
2 ;
no rows selected
It means, Oracle changes the data dictionary in the DDL triggers but rollbacks the transaction if error occurs in the trigger.