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From Nurullah Akkaya <nurullah_akk...@yahoo.com>
Subject Re: keeping the table ordered
Date Tue, 06 Feb 2007 17:14:02 GMT
> It is not quite clear to me what you are trying to achieve.  Why do  
> you want a sequential read?  Scanning the entire table of 100  
> million records should take longer time than looking up a record  
> using a index on wordid.  Have you retrieved the query plan and  
> made sure the index on wordid is used?  Or are you talking about  
> doing a lookup of many different wordids in sorted order?
>

i did not meant sequential scanning of the whole table i meant disk i/ 
o( bottom paragraph explains it )
yes i checked the query plan and derby uses index to lookup records  
and index look up checks only two index pages. so i came to the  
conclusion that most of the time is lost making random i/o request  
for the data thats why i am trying to keep the table sorted. since  
sequential hard disk access is much faster than random i/o .



On Feb 6, 2007, at 8:09 AM, Michael Segel wrote:


>>
>>
>
> What exactly are you trying to do?
> Based on the little snippet, it looks like this is an exercise to  
> create a
> "google like" search on a series of documents.
>
> The problem is that your wordID, while an integer, is not going to  
> be unique
> enough.
>

wordId isn't unique at all each word in a document gets a  
corresponding posting entry i look up wordId for the word the then  
select all docId's containg the wordId. that posting list is basicly  
a big inverted list. what i am trying to do is keep the table sorted  
by wordId so insted of keeping values randomly on disk they are being  
written sequentialy to the file so that instead of doing random i/o i  
just do a sequential read from the hard drive. i don't want   
sequential scanning of the whole table.


>
> For example, search your documents where the wordID is the integer  
> look up for
> the word "the".
>
> Do you see the problem?
>
> -- 
> --
> Michael Segel
> Principal
> Michael Segel Consulting Corp.
> derby -=-@segel.com
> (312) 952-8175 [mobile]
>






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