Is it possible to set user defined session/connection flag for use in trigger? - sql

Question

Consider a trigger that sets an id-column to an Oracle-sequence (next-)value on-insert. Now I want to extend it with some extra debugging actions. But they should be only active for certain connection/sessions (i.e. debugging ones).
Pseudo-Code on client side:
Open connection to oracle database
set mydebugflag=yes for that connection only
insert some stuff
close connection
Pseudo-Code on server-side (inside the trigger):
set id = someseq.next_val
if mydebugflag=yes then { do_some_extra_sanity_checks(); diagnostics();}
else: finished
How to implement such logic for an Oracle database?
Which Oracle features should I use for this?

Answer 1

There are a couple of ways to do this.
One is to create a package, create a package global variable (which will have session scope) in the package, and then have your client set the package variable and your trigger read it. Something like
CREATE OR REPLACE PACKAGE pkg_debug_mode
AS
PROCEDURE set_debug_mode( p_debug_mode IN NUMBER );
FUNCTION get_debug_mode
RETURN NUMBER;
DEBUG_MODE_ON constant number := 1;
DEBUG_MODE_OFF constant number := 2;
END;
CREATE OR REPLACE PACKAGE BODY pkg_debug_mode
AS
g_debug_mode NUMBER := DEBUG_MODE_ON;
PROCEDURE set_debug_mode( p_debug_mode IN NUMBER )
AS
BEGIN
g_debug_mode := p_debug_mode;
END;
FUNCTION get_debug_mode
RETURN NUMBER
IS
BEGIN
RETURN g_debug_mode;
END;
END;
The client calls pkg_debug_mode.set_debug_mode to set the debug mode and the trigger calls pkg_debug_mode.get_debug_mode to determine the current debug mode for the session.
create or replace context my_ctx using pkg_debug_mode;
CREATE OR REPLACE PACKAGE BODY pkg_debug_mode
AS
PROCEDURE set_debug_mode( p_debug_mode IN NUMBER )
AS
BEGIN
dbms_session.set_context( 'MY_CTX', 'DEBUG_MODE', p_debug_mode );
END;
FUNCTION get_debug_mode
RETURN NUMBER
IS
BEGIN
RETURN SYS_CONTEXT( 'MY_CTX', 'DEBUG_MODE' );
END;
END;
Your trigger can either call the get_debug_mode function or it can directly reference the context by putting the SYS_CONTEXT call in the trigger.