Stop SQL statements without schema qualifiers - oracle

Question

How can I stop a SQL statement from running if it's missing a schema qualifier? Most of these issues are caught by a development process, but is there a way to stop the ones that slip through the cracks?
For example, this statement should work:
create table jheller.test_table(a number);
This statement should fail:
create table test_table(a number);
Most of these problems are easily caught during development. Usually a lack of privileges will cause an error like ORA-00942: table or view does not exist. Or if the statement runs successfully on the wrong schema it will cause an obvious error that will be caught during testing.
But inevitably some bad statements still make it into deployments that are promoted to the upper environments. This leads to broken deployments and invalid objects created in schemas like SYS. (We shouldn't be running so many deployments as SYS but that's beyond our control.)
It's not necessary to catch 100% of these issues. But catching 99.9% instead of 99% would make a significant difference.

Answer 1

SQL statements without schema qualifiers can be prevented by:
Creating a fake, empty schema on all databases.
Creating a database trigger to prevent creating objects in that schema.
Setting the session variable CURRENT_SCHEMA to that schema at the beginning of deployment scripts.
Installation - run once per database.
--Create a user. It won't be used so lock it and don't grant it any privileges.
create user schema_qualifier_required identified by "[SOME RANDOM PASSWORD HERE]";
alter user schema_qualifier_required account lock;
--Create trigger to prevent any other user from creating objects on it.
create or replace trigger schema_qualifier_required.no_objects_on_schema_qualifier
before ddl on database
/*
Purpose: SCHEMA_QUALIFIER_REQUIRED exists only to help prevent statements
without schema qualifiers. This trigger ensures no objects can be created in
the schema.
Run this command in a session to help ensure schema qualifiers are used:
alter session set current_schema=schema_qualifier_required;
To drop or modify the schema this trigger must be dropped like this:
alter system set "_system_trig_enabled"=false;
drop trigger schema_qualifier_required.no_objects_on_schema_qualifier
alter system set "_system_trig_enabled"=true;
*/
begin
if ora_dict_obj_owner = 'SCHEMA_QUALIFIER_REQUIRED' then
raise_application_error(-20000, 'You cannot create objects in this schema. '||
'Did you forget to use a schema qualifier in your statement?');
end if;
end;
/
Non-qualified statements initially work.
SQL> create table test1(a number);
Table created.
SQL> select * from test1;
no rows selected
ALTER SESSION to prevent future non-qualified statements from running.
SQL> alter session set current_schema=schema_qualifier_required;
Session altered.
Non-qualified statements no longer work.
SQL> create table test2(a number);
create table test2(a number)
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-20000: You cannot create objects in this schema. Did you forget to use a
schema qualifier in your statement?
ORA-06512: at line 3
SQL> select * from test1;
select * from test1
*
ERROR at line 1:
ORA-00942: table or view does not exist
I have not used this method in production yet. If anyone sees problems with this approach or knows of a better way please edit, comment, or add another answer.