Strange..!!! Can u tell me why this ?

Hello Friends,
I found very a strange thing about postgres Database. I am running
postgres under Linux operating system.

I am having a website in PHP and having one perl program which runs
every friday to generate a report. The size of thsi postgres DB is
near about 5-7 MB.

In the start when records were less in the DB the file too around 3 to
mins to generate a report we called as Friday report. The web pages
were also coming fast in the browser. So I was quite happy abt the
performanance.

But Later on as the DB size get increased the time was also get
increased. And at one point i noticed the time required to gererate
this report is very high near abt 10 to 15 hrs. So I checked for
performanance.

Site was also become very slow. A simple page which is fetching just
20 records, for that also I got the error page not displayed.I tried
my level best to find out the problem. But I couldn't...!!! :-((

So at last I decided to drop DB and recreate once more after taking
backup of data. And I did that. After that i was surprised that site
become very very fast. And the pages for which I got the error comes
in less than 10 seconds.

So can u tell me why this happens ? Why suddenly DB performanance get
increased so fastly ? Prev.ly I tried for vacuumdb also....

If anybody there knows the reason for this please reply me.

Thanx in advance.
Pandurang
pandurang(at)manas-solutions(dot)com
http://www.geocities.com/pandurang_g/