disqus comments, part 2

I have decided to remove disqus comments. What I considered to be a bonus, that is CODE POSTING, appears to be worst than before, because the PRE tag does not work.

The main reason I switched back to last week behavior is that the COMMENT FEED does not work any longer. And I hate changes that annoy my readers.

I will keep looking for a comment plugins that allow posting of code

alert log in xml format

The alert log is in xml format in Oracle 11g. If you want to parse the content of the file and use the XML functions to retrieve the data, you can use this way :

SQL> create or replace directory alert as
  2    '/app/oracle/diag/rdbms/lsc01/lsc01/alert';

Directory created.

SQL> var c clob
SQL> declare
  2     b bfile := bfilename('ALERT','log.xml');
  3  begin
  4     dbms_lob.open(b,dbms_lob.file_readonly);
  5     dbms_lob.createtemporary(:c,true);
  6     dbms_lob.loadfromfile(:c,b,dbms_lob.lobmaxsize);
  7  end;
  8  /

PL/SQL procedure successfully completed.

SQL> select extractvalue(xmlparse(content :c),
  2    '/msg[@time="2008-03-30T01:01:13.704+01:00"]/txt/text()')
  3  from dual;

Starting ORACLE instance (normal)

Disqus comments

I just replaced the default wordpress comments by Disqus comments. Disqus enable you to track your comments add picture and other fancy staff.

I have been looking for such a plugin for a very long time (and was too foul to develop it myself).

The amazing bonus with Disqus is that you can post code! Your x<1 will be code in code, not a pseudo html tag annoying more than one of my fellow reader.

Feel free to test it on this post.

Thanks to Yas for making me discover this on : Oracle Today

I hope I will not have have to many issues with this new plugin! Feedback welcome

oradebug tracefile_name

I have enabled tracing in a session and now I want to retrieve the name of the tracefile.

Ex: my session has sid 335.

How do I retrieve trace file name from sqlplus ?

select pid from v$process where addr in 
(select paddr from v$session where sid=335);


Now I can use oradebug to reveal tracefile name

SQL> oradebug setorapid 47
Unix process pid: 1372408, image: oracle@dbsrv01 (TNS V1-V3)
SQL> oradebug tracefile_name

Read valuable information about oradebug on this site, amoung others

To RR or to YY ?

What is worst? To use DD-MON-RR or to use DD-MON-YY? When entering the birthday of my grandfather, I will write it as 31-JUL-1912, so both formats will be fine. If I enter it 31-JUL-12, both formats will be wrong. Ok, which date will I enter now and in the future? For short-time contracts I will enter dates like 01-AUG-08 or 31-DEC-11, both formats will be fine. For long time contracts like retirement saving plan I will enter 31-MAR-36, which is still fine, because I am old enough :mrgreen: Juniors in my company will enter dates like 30-JUN-52, which will be fine with YY and wrong with RR or RRRR.

Ok, what is the recommended format then?

DD-MM-FXYYYY is probably fine. FX forces you to enter 4-digits years.

SQL> select
  2    to_date('31-JUL-1912','DD-MON-YY') YY1912,
  3    to_date('31-JUL-12','DD-MON-YY') YY12,
  4    to_date('31-JUL-12','DD-MON-RR') RR12
  5  from dual;

YY1912     YY12       RR12
---------- ---------- ----------
1912-07-31 2012-07-31 2012-07-31

SQL> select
  2    to_date('31-MAR-2036','DD-MON-YY') YY2036,
  3    to_date('31-MAR-36','DD-MON-YY') YY36,
  4    to_date('31-MAR-36','DD-MON-RR') RR36
  5  from dual;

YY2036     YY36       RR36
---------- ---------- ----------
2036-03-31 2036-03-31 2036-03-31

SQL> select
  2    to_date('30-JUN-2052','DD-MON-YY') YY2052,
  3    to_date('30-JUN-52','DD-MON-YY') YY52,
  4    to_date('30-JUN-52','DD-MON-RR') RR52
  5  from dual;

YY2052     YY52       RR52
---------- ---------- ----------
2052-06-30 2052-06-30 1952-06-30

SQL> select
  2    to_date('8/4/2008','DD-MM-FXYYYY') FXYYYY2008
  3  from dual;


SQL> select
  2    to_date('08-04-08','DD-MM-FXYYYY') FXYYYY08
  3  from dual;
  to_date('08-04-08','DD-MM-FXYYYY') FXYYYY08
ERROR at line 2:
ORA-01862: the numeric value does not match the length 
of the format item


Obfuscation contest

I have been challenged to participated (my script : lsc2.sql) and now challenged to explain my query by Chen
Chen Shapira

Ok, I give a try.

To make the query unreadable and unformatable I used no space, no new line, and I started by q’<'>‘ to confuses sqlinform.

Ok, I added undocumented constructs like

connect by .1 < 1.
connect by .25 > rownum/100.

with 2 connect by, the first is ignored. The second is buggy in 10gR1 and returns 25 rows in 10gR1 (but 24 rows in 9i, 10gR2, 11g).

and group by () which means only one group. Note this clause is mandatory, you cannot remove it when using an aggregate function and a scalar subquery like in
select (select 1 from dual), count(*) from dual group by ();

The utl_raw and to_char converts a number to the string Oracle Community. I will keep terse on the formula.
The scalar subquery inside TAN returns 1. The regexp removes some characters out of the extract tag. _x0032_ is the alias of the column “2”. The v$reservedwords use UNIQUE to sort the rows (UNIQUE was sorting in 10gR1 for UNIQUE/DISTINCT) and the MAX(rownum) retrieve the 316th row (FROM) and 845th row (SELECT). Remember ROWNUM is evaluated BEFORE aggregation, therefore ROWNUM 845 exists! Note the “+” is an alias and not a string!

With the SELECT and FROM keyword I build a new query that I dynamically evaluates with dbms_xmlgen.getxml. Rest of the first part is fancy calculation.

The dburi is also dynamic.


Well, I could have obfuscated the text a bit more but I was short of time… This simply return the name of the package that have a procedure called GETKEY. Which is DBMS_OBFUSCATION_TOOLKIT_FFI. This is not very clean as the query would fail if you have a PROC.GETKEY in your schema. Well, I wanted to add this not very well know mechanism to query the database.

Last part is in dict, I select the pattern ‘[COTTON+XE]{4,}’ in dict and return the Mode (or modal score), which is CONTEXT.

A bit formatting and I get

Oracle Community_Obfuscation_Contest

Side effect of cursor sharing

Cursor sharing transform strings in bind variable.

So if you do SELECT * FROM EMP WHERE ENAME='SCOTT'; it will be transformed in SELECT * FROM EMP WHERE ENAME=:sys_b0;

This sometimes improved performance of application that do not use binds, for instance.

Now let’s imagine your application generates trace files. The application generates a SELECT 'LSC-11.1011.000.1110.1.0100.000.110' FROM DUAL;
. Ok, let’s look for the string in trace files :

$ cd udump
$ grep LSC-11 *.trc
$ grep DUAL$ *.trc
LSC01_ora_8630490.trc:SELECT :"SYS_B_0" FROM DUAL
LSC01_ora_8630490.trc:SELECT :"SYS_B_0" FROM DUAL
LSC01_ora_8839288.trc:SELECT :"SYS_B_0" FROM DUAL
LSC01_ora_8839288.trc:SELECT :"SYS_B_0" FROM DUAL
LSC01_ora_8933560.trc:SELECT :"SYS_B_0" FROM DUAL
LSC01_ora_8933560.trc:SELECT :"SYS_B_0" FROM DUAL

WTF! The tracing mechanism of the application is no longer usable 😈

Another side effect is the length of the column and is described there : http://asktom…P11_QUESTION_ID:3696883368520