From: Michael Neumann <neumann@...>
Date: 2001-10-09T21:44:37+09:00
Subject: [ruby-talk:22302] Re: What's wrong with these Arrays?

Jens Rohde wrote:
> Hi ruby-hackers
> 
> I'm working on a script that are supposed to analyse the logfiles from my
> cisco PIX firewall.
> 
> One of the tasks is to find the first and the last date a given ip-address
> has done a violation. For that I've produced the following code:
> 
> theIP.each do |plof| # Traverse the list with violating IP's
>   sql = "select date from pixlog where srcIP = \"#{plof}\" order by date"
>   getData = @dbHandle.prepare(sql); getData.execute
>   tempArray = Array.new
>   while tempVar = getData.fetch do
>     tempArray.push(tempVar)

replace above line with:

     tempArray.push(tempVar.dup)

>   end
>   firstDate = tempArray[0].to_s
>   lastDate = tempArray.last.to_s
>   @report.push("From "+firstDate+" to "+lastDate+" "+plof+" ...
> end
> 
> For some reason tempArray alwas seems to be filled with the last value
> delivered by the getData-fetch command.

It seems that you use Ruby/DBI for DB access.
StatementHandle#fetch (and all the other similar methods) return
a reference to an internal array where the columns of each requested row 
are stored in => DBI only creates one Array instead of one for each row.
If you want to store one row completely elsewhere you have to duplicate it
using method "dup"; if you just use some fields of a row, you don't have to do so.

I'd rewrite you're piece of code as follows:

   sql = "select date from pixlog where srcIP = ? order by date"
   getData = @dbHandle.prepare(sql)

   theIP.each do |plof| # Traverse the list with violating IP's
     getData.execute(plof)
     dates = getData.collect {|row| row['date']}   # store only the dates not the whole rows

     @report.push("From "+dates.first+" to "+dates.last+" "+plof+" ...
   end


And if you're database supports "fetch_scroll", I'd use this instead for increasing
performance.


Regards,

  Michael

-- 
Michael Neumann
merlin.zwo InfoDesign GmbH
http://www.merlin-zwo.de