RE: What stupid mistake am I making with this onlogin trigger?

From: Powell, Mark D <mark.powell_at_eds.com>
Date: Tue, 26 Feb 2008 09:09:10 -0500
Message-ID: <D1DC33E67722D54A93F05F702C99E2A90201BD12@usahm208.amer.corp.eds.com>

 

I have not tested it recently but the sys_context call used to be significantly slower than just issuing
select sid from v$mystat where rownum = 1

This form of the query will eliminate the need to read all 370 or so rows and then through away the duplicates.

• Mark D Powell -- Phone (313) 592-5148

-----Original Message-----

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Nigel Thomas Sent: Tuesday, February 26, 2008 7:14 AM To: Jay.Miller_at_tdameritrade.com; oracle-l_at_freelists.org Subject: Re: What stupid mistake am I making with this onlogin trigger?

Small extra point:

IMHO it's not best practice to use v$ views when you could use SYS_CONTEXT and DBMS_APPLICATION_INFO instead - so you don't have to have too many users with unrestricted read access to some or all of the v$ views. It's always a good idea to minimise the scope of any grants.

(select unique(sid) from v$mystat)

can be replaced with:
  SYS_CONTEXT('userenv','sessionid')

which has the added benefit of avoiding a hash(unique) on v$mystat (370 rows in my case).

To demonstrate:

declare

 l_module varchar2(48);
 l_action varchar2(32);
 l_username varchar2(30);
 l_sid integer;

begin
 dbms_application_info.read_module_info(l_module, l_action); l_username := sys_context('userenv','session_user');  l_sid := sys_context('userenv','sessionid');

 dbms_output.put_line('User:'||l_user||', SID:'||l_sid||', Module:'||l_module);

end;
/

Shame that DBMS_APPLICATION_INFO doesn't have usable GET_xxx functions, but forces the use of a procedure with output parameters. How 1960s is that? Also, in some circumstances it might be appropriate to cover DBMS_APPLICATION_INFO with a package that only allows gets, not sets.

NB I haven't compared the cost of these with accessing the views.

Regards Nigel

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http://www.freelists.org/webpage/oracle-l Received on Tue Feb 26 2008 - 08:09:10 CST