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Date: Wed, 23 Jan 2013 01:33:03 +1100
Subject: Re: Using filepath method to identify an .html page
From: Chris Angelico <rosuav@gmail.com>
To: python-list@python.org
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On Wed, Jan 23, 2013 at 12:57 AM, Ferrous Cranus <nikos.gr33k@gmail.com> wr=
ote:
> =D4=E7 =D4=F1=DF=F4=E7, 22 =C9=E1=ED=EF=F5=E1=F1=DF=EF=F5 2013 3:04:41 =
=EC.=EC. UTC+2, =EF =F7=F1=DE=F3=F4=E7=F2 Steven D'Aprano =DD=E3=F1=E1=F8=
=E5:
>
>> What do you expect int("my-web-page.html") to return? Should it return 2=
3
>> or 794 or 109432985462940911485 or 42?
>
> I expected a unique number from the given string to be produced so i coul=
d have a (number <=3D> string) relation. What does int( somestring ) is ret=
urning really? i don;t have IDLE to test.

Just run python without any args, and you'll get interactive mode. You
can try things out there.

> This counter.py will work on a shared hosting enviroment, so absolutes pa=
ths are BIG and expected like this:
>
> /home/nikos/public_html/varsa.gr/articles/html/files/index.html

That's not big. Trust me, modern databases work just fine with unique
indexes like that. The most common way to organize the index is with a
binary tree, so the database has to look through log(N) entries.
That's like figuring out if the two numbers 142857 and 857142 are the
same; you don't need to look through 1,000,000 possibilities, you just
need to look through the six digits each number has.

> 'pin' has to be a number because if i used the column 'page' instead, jus=
t imagine the database's capacity withholding detailed information for each=
 and every .html requested by visitors!!!

Not that bad actually. I've happily used keys easily that long, and
expected the database to ensure uniqueness without costing
performance.

> So i really - really need to associate a (4-digit integer <=3D> htmlpage'=
s absolute path)

Is there any chance that you'll have more than 10,000 pages? If so, a
four-digit number is *guaranteed* to have duplicates. And if you
research the Birthday Paradox, you'll find that any sort of hashing
algorithm is likely to produce collisions a lot sooner than that.

> Maybe it can be done by creating a MySQL association between the two colu=
mns, but i dont know how such a thing can be done(if it can).
>
> So, that why i need to get a "unique" number out of a string. please help=
.

Ultimately, that unique number would end up being a foreign key into a
table of URLs and IDs. So just skip that table and use the URLs
directly - much easier. In this instance, there's no value in
normalizing.

ChrisA