On 22/06/2007, at 11:10 PM, Michael Gentry wrote:
> Marcin, this thread might be of interest to you ...
>
> http://mail-archives.apache.org/mod_mbox/cayenne-dev/200705.mbox/
> browser
>
> Look at the "Paging and SQL queries" thread on May 25.
Yes, this is the same project we are working on. I started some
performance profiling and Marcin has been able now to take it much
further. What is it about:
> elements.add(it.nextObjectId(entity));
which is so slow? The code gets a little complex at that point and we
are having difficulty tracing it through to the exact performance
problem in the underlying code. Is it the speed of adding the object
id to the Collection or the speed of creating an object id itself?
0.5ms doesn't sound slow, but it doesn't scale well.
Andrus, I got the impression from the previous thread that you
suspected something slightly different. That the performance problem
might be in the fat query itself, but from our tests this isn't the
case. If I've got this right, the way it works is:
1. perform regular query to get all columns but return result in
iterator
2. iterate through first page and build full objects
3. iterate through other pages and build just objectids (this is the
slow part for us)
4. when another page is fetched perform another query and fetch those
objects from the DB
So, getting just primary keys from the DB may not be any faster if
the performance problem is simply in the construction of objectIds.
If the performance problem is in the numerous resizings of the
Collection (each time it runs out of space, then it is increased by
50% or 100% in size), then the solution could be as simple as
figuring out the size of the iterator and sizing the collection
appropriately from the beginning.
Any ideas on how to discover the exact cause of the performance hit?
Ari Maniatis
-------------------------->
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