Pawel Barut

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My thoughts about developing software. Problems descriptions and solutions, tips, tricks, links to useful resources. Mostly on Oracle, but also PHP, Delphi and other languages & tools.
Updated: 3 hours 3 min ago

Spam, Spam filters, Being Spammer, Being Filtered-out ...

Sun, 2008-02-03 11:46
Written by Paweł Barut
My thoughts about Spam. Some time agou I wrote about spam in comments on my blog, but this time it will be about email spam. This is something that from time to time irritates me a lot. Spam is something that nobody wants to see in his mails. And to solve this problem there are many spam filters, IP Block lists and other solutions. But none of them is 100% accurate. And this is what causes problems. Spam filers should be solving problems, but many times creates new ones.
In ideal situation spam filter eliminates 100% of spam, and passes 100% of emails that are expected by users. But it's not true. I will now show example situations, that lead me to conclusion, that spam filter are useless.
Situation 1.
Spam filter did not recognized spam mail, and I have to manually figure out that this is spam. So I need to one more click to delete message.
Situation 2.
Spam filter deletes mail that was intended for me. This was false alarm as it wasn't spam.
Situation 3.
I've send email to customer/friend. His spam filter blocked it. I did not received any delivery failure message.

In my opinion situation 2 and 3 are very dangerous and I would like to avoid any of those situations. In my opinion those situations makes spam filters useless. It is especially dangerous if this block is done by service provider, and when you cannot see list of spam being filtered out. This is what really annoys my and makes me angry. In fact it makes whole email system unreliable (I do not want to say useless), as you never know if you recipient get your email or not.

I do not know what is solution for this. I can see few options, but none of them is perfect:
  1. Each and every email should be signed digitally by sender, and additionally by his service provider. Spam filers should be able to verify this and honor such signing, and not consider this to be spam. Of course spammers could find way to sign theirs mail too, and vanish this approach.
  2. Everybody should use "return receipt" to confirm mail delivery. Well, quite simple, but personally I never allow my mailer to send confirmations, as I do not want to reveal when I've read mail.
  3. Make mail system payable. So for every mail you send you have to pay small amount of money. $0.01 per email should not be problem for real email users, but could cost fortune for spammers. For this money service providers should ensure that your mail will reach recipient.
  4. Use captcha to validate that email is send by real user. I could work as this: when spam filter suspects spam, it sends back email to sender with link to web page on which user will have to provide answer to captcha to make his mail pass throu spam filter.

At the end I would like to ask you: How do you deal with spam?

Cheers Paweł

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Categories: Development

How to shrink Oracle Context Index

Wed, 2008-01-23 14:50
On of databases I've found that one of Context Indexes is getting bigger and bigger everyday. It was around 5-10% grow per day for table DR$MY_TEXT_I$I which contains tokens(word). No of records indexed was almost the same, but index grown was unexpectedly big. It was due fact, that quite many rows were modified every day, and it caused re-indexing those rows during index synchronization (CTX_DDL.SYNC_INDEX). So I've decided to reclaim this space.
Method 1.This was my first though:
  • Drop Index ... /Create Index ...
  • or Alter Index ... Rebuild
But those methods have some disadvantages:
  • Users cannot perform text searches during this operation,
  • It does not solve problem for longer time, as index will still grow ...
So I had to find root cause and eliminate it.
Method 2.While looking for root cause I've find out, that Index has never been optimized, so it kept old (obsolete) data. My solution was:
SQL> exec ctx_ddl.optimize_index('MY_TEXT_I', 'FULL', 120);
SQL> alter table DR$MY_TEXT_I$I enable row movement;
SQL> alter table DR$MY_TEXT_I$I shrink space cascade;

With this method table DR$MY_TEXT_I$I took 30% of its original size.
So let me explain why this worked. With ctx_ddl.optimize_index context index was internally optimized. It means information about old documents were completely deleted and index was internally minimized. Remember - third parameter limits time (in minutes) allowed for optimization. If it is really big index it can take hours. But you can run this optimization many times, until your index will be fully optimized.
Then I've just shrunk table (shrink space cascade). But this operation requires to enable row movement on table first.

But this was one time operation. To avoid this problem in future I've scheduled job to run ctx_ddl.optimize_index on regular basis. Now this table has grown a little, but is no longer growing so fast.

Foot note:
  • It was tested on Oracle EE 10gR2 (10.2.0.3),
  • I'm not sure if row movement is supported by Oracle for Context Index table DR$<index>$I. It worked for me and I did not experience any problems since turning it on.


Cheers, Paweł
Categories: Development

I've been tagged 3 times; 8 things about me

Sat, 2008-01-12 10:17
Few busy days without any blog reading and after I've gone through my feeds it occurred that I've been tagged 3 times:
  1. By Eddie Awad
  2. By H.Tonguç YILMAZ
  3. By Jorrit Nijssen (Jornica)
Thanks You for tagging.
Now I feel that I really need to write something about me:
  1. I was born and grow up in Krosno in south-east Poland (see satellite picture),
  2. I 15th when Communism fall down in Poland. At this moment Poland is member of Schengen Agreement, and I can travel around Europe without passport. Lot of changes in last 19 years,
  3. I'm Thawte Web of Trust Notary,
  4. In 1993 I took 2nd place in Nation Contest in Programming for College Students. Unfortunately I was 6 month too old to take part in international final :(
  5. In 1990 I've sold my first program; small DB written in Clipper. I did not think that this program will be used for so many years. In 1999 I had to do some changes to support year 2000,
  6. My first program was written in Basic and was run on PSP-80 (page in Polish)
  7. I'm married and we have 2 daughters (6 and 2 years old),
  8. My favourite TV show is Top Gear with Jeremy Clarkson , Richard Hammond and James May.
I will not invite anyone directly as I do not want to accused of spam. All my readers that have blogs are welcome to post 8 things about themselves.

Cheers,
Paweł
Categories: Development

Do not trust Google Maps

Wed, 2007-12-05 11:23
Ok, Might be title is too strong, but you should not trust Google Maps when searching for streets in Krosno, Poland (city where I was born). Here is sample, try to search for "Lwowska, 38-400 Krosno, Poland" and you get:
Search is working correctly, but names on street do not match reality. Instead of "Lwowska" street is "Jana Lenarta". Another example is "Platynowa" instead of "Podkarpacka". It seems that all street names are messed up on map. Hope they fix it soon.

Cheers, Paweł
Categories: Development

Rant: Great fun with Wii

Sun, 2007-12-02 04:48
I'm not a computer game player, but Nintendo Wii really impressed me. I was with a visit to my friend and he showed me his new gadget. We started to play for a while, and time passed by. It's really addictive. The best thing is that you do not seat at computer and use joystick or keyboard, but you stand up and move whole body to play. It really gives pleasure, and we have good time. If you do not know Wii yet check this Wii commercial.

Have fun
Paweł
Categories: Development

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