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From Abdullah Kauchali <abdullah.kauch...@isanusi.com>
Subject Re: R: What is N+1
Date Wed, 09 Feb 2005 15:32:36 GMT

I can see the point when friendlyVU (???) spoke about getting details of 
the appropriate parent. 
"Appropriate" being the operative word.  (Lazy loading)

In all our database applications, we have *seldom* required the need to 
work off a list of
Categories then require to display (use) all the children of the 
different Categories viz. all the
different products of the *different* Categories.  We never needed it 

What we have required, however, is the proces the other way round.  
Where we work off a list of Products
and while busy with them we require the details of their Categories.  
So, it is n+1 the other way

Currently we are using a second select with a IN statement containing a 
comma delimited entries
of the unique parents.  We then do the "mapping" in code.

What are your thoughts on this?

Kind regards


Clinton Begin wrote:

>I'm not sure what you're point was, but N+1 selects is THE most common
>relational databases performance problem caused by application
>developers today.
>Understanding it is critical if you want to avoid making this mistake.
> Not every application will have the luxury of simply being 1:1
>Table:Screen.  In fact, I've almost never seen this to be the case in
>enterprise applications.
>Consider a 3 tier hierarchy like in JPetStore:  Categories -1---M-
>Products -1----M- Items.
>For illustration purposes, the number of queries to load this data
>with an immediate or lazy load strategy is:
>1 * count(categories) * count(Products)

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