Re: What is N+1

[Vic Cekvenich]

Which I could do with a join on SQL side. I can't see how this is 
something I'd use or how it' scale, but.... I guess somone uses it.
THANKS for the education.
.V

Kris Jenkins wrote:

The N+1 selects problem is when you query for n parents, and you need 
one extra query for the children.  Internally, this happens:

   List parents = sqlMap.queryForList( "getParents", parameter );
   for ( Iterator i = parents.iterator(); i.hasNext(); ) {
      Parent p = (Parent) i.next();
      List children = sqlMap.queryForList( "getChild", p.getId() );
      p.setChildren( children );
   }
So you end up with 1 query for the parent list, plus one extra for 
each parent to get the children = n + 1.  Rather inefficient.
This is the problem that 2.0.9 fixes.

Sorry for the confusion.
Kris

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