Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Mailing Lists -> Oracle-L -> Re: Find an unprintable character inside a column....

Re: Find an unprintable character inside a column....

From: <Jared.Still_at_radisys.com>
Date: Fri, 10 Oct 2003 14:29:24 -0800
Message-ID: <F001.005D2B9E.20031010142924@fatcity.com>


Always glad to be of service.

It works with translate(), about 53% faster.

Stephane Faroult <sfaroult_at_oriole.com>
Sent by: ml-errors_at_fatcity.com
 10/10/2003 02:54 PM
 Please respond to ORACLE-L  

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
        cc: 
        Subject:        Re: Find an unprintable character inside a column....


Jared.Still_at_radisys.com wrote:
>
> I played with this a bit.
>
> First, I created some test data with one column corrupted with a
> single random character
> of 0-31 replacing a random char in that column 20% of the rows of the
> table.
>
> Peter's function correctly found all of the rows in 7.5 seconds.
>
> Stephane's function ran in 3.5 seconds, but didn't find any of
> the rows. I didn't attempt to correct the code.
>
> Then I tried a function based on owa_pattern.regex. My initial
> attempts
> didn't return the correct rows, as the regex pattern needed some
> tuning.
>
> I didn't attempt to fix it, as it was woefully slow, about 30 seconds.
>
> Regex in the WHERE clause in 10g will be nice.
>
> Jared
>
> "Stephane Faroult"
> <sfaroult_at_oriolecorp.com> To: Multiple
> Sent by: ml-errors_at_fatcity.com recipients of list ORACLE-L
> <ORACLE-L_at_fatcity.com>
> 10/10/2003 07:09 AM cc:
> Please respond to ORACLE-L Subject: RE: RE:
> RE: Find an unprintable character
> inside a column....
>
> >Some people have requested this code, so I thought
> >you might as well all
> >have the chance to pick it to bits... Its a
> >function called BAD_ASCII, and
> >it hunts out for any ascii characters with an ascii
> >value of less than 32 in
> >a specified field. (Acknowledgments to my colleague
> >Keith Holmes for help
> >with this code.)
> >
> >Use it as follows:
> >
> >Where a field called DATA in a table TABLE_1 may
> >contain an ascci character
> >with a value less than 32 (ie a non-printing
> >character), the following SQL
> >will find the row in question:
> >
> >select rowid,DATA,dump(DATA) from TABLE_1
> >where BAD_ASCII(DATA) > 0;
> >
> >You could use the PK of the table instead of rowid,
> >of course. You will also
> >note that I select the DATA field in both normal
> >and ascii 'dump' mode, the
> >better to locate where the corruption is located.
> >
> >peter
> >edinburgh
> >...................................
> >
> >Source as follows:
> >
> >
> >Function BAD_ASCII
> > (V_Text in char)
> > return number
> >is
> > V_Int number;
> > V_Count number;
> >begin
> >--
> >V_Int := 0;
> >V_Count := 1;
> >while V_Count<=length(rtrim(V_Text)) and V_Int=0
> > loop
> > if ascii(substr(V_Text, V_Count, 1))<32 then
> > V_Int := V_Count;
> > end if;
> > V_Count := V_Count + 1;
> >end loop;
> >return V_Int;
> >--
> >exception
> > when others then
> > return -1;
> >end BAD_ASCII;
> >/
> >
>
> Peter,
>
> I think that you can make this code 25% faster when the data is
> clean (which hopefully is the general case) by using 'replace', more
> efficient than a PL/SQL loop, to check whether you have some rubbish
> (sort of). It will not tell you where the bad character is, however -
> which means that then you can loop to look for it.
>
> Here is what I would suggest :
>
> create or replace Function BAD_ASCII (V_Text in char)
> return number
> is
> V_Int number;
> V_Count number;
> begin
> if (replace(V_text, chr(0)||chr(1)||chr(2)||chr(3)||
> chr(4)||chr(5)||chr(6)||chr(7)||
> chr(8)||chr(9)||chr(10)||chr(11)||
> chr(12)||chr(13)||chr(14)||chr(15)||
> chr(16)||chr(17)||chr(18)||chr(19)||
> chr(20)||chr(21)||chr(22)||chr(23)||
> chr(24)||chr(25)||chr(26)||chr(27)||
> chr(28)||chr(29)||chr(30)||chr(31),
> '--------------------------------')
> = V_text)
> then
> return 0;
> else
> V_Int := 0;
> V_Count := 1;
> while V_Count<=length(rtrim(V_Text)) and V_Int=0
> loop
> if ascii(substr(V_Text, V_Count, 1))<32 then
> V_Int := V_Count;
> end if;
> V_Count := V_Count + 1;
> end loop;
> return V_Int;
> end if;
> --
> exception
> when others then
> return -1;
> end BAD_ASCII;
> /

Jared, you're the scourge of people who just write things out of the top of their head and don't test them thoroughly :-). I had made my usual mistake of using REPLACE instead of TRANSLATE. Just tried it with 'regular' data, since this is the only case where it can be faster that Peter's routine.
Works like Peter's routine with TRANSLATE, only somewhat faster.

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: 
  INET: Jared.Still_at_radisys.com

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).
Received on Fri Oct 10 2003 - 17:29:24 CDT

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US