Reduce or Transformers

[Krzysztof Pajak]

Hello Ayende

What is more efficient: Reduce or Transformers ?

When I use Transformers I had to put in my query "Take(int.Max)" and also change config file (<add key="Raven/MaxPageSize" value="2147483647"/>) 

- and it works slowly. 

My sample transformer looks like this:

                TransformResults = products => from prod in products

                                               from manuf in prod.ProductManufacturers

                                               group manuf by manuf.ManufacturerId into g

                                               select new

                                               {

                                                   Id = g.Key,

                                                   Count = g.Count()

                                               };

Thanks for the help.

Regards

Krzysztof

[Oren Eini (Ayende Rahien)]

Reduce is _far_ more efficient.

Please note that by explicitly configuring max page size, especially to such a high value, you are effectively force the system to do a LOT more work, none of which it was designed to do.

If you need to do aggregation, that is why we have map/reduce for.

Hibernating Rhinos Ltd  

Oren Eini l CEO l Mobile: + 972-52-548-6969

Office: +972-4-622-7811 l Fax: +972-153-4-622-7811

 

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[Krzysztof Pajak]

Great, thanks for quick response!

[Krzysztof Pajak]

If I can't use Transformers, how can I use reduce for query.

My sample object Product has field:

Id, Name, Published, Deleted, List<Categories>, List<Manufacturers>

My sample query:

var query = session.Query<Product>();

query = query.Where(x=>x.Deleted == false);

query = query.Where(x=>x.Categories.Any(new int[1,2]);

I need show List of manufacturers with count of products.

BTW my query has dynamic parameters.

Previously I was using the Transformers and resolved this.

 

Thanks for the help.

[Oren Eini (Ayende Rahien)]

Include the dynamic parameters in the reduce definition, or use dynamic aggregation.

http://ravendb.net/docs/article-page/2.5/Csharp/client-api/querying/dynamic-aggregation

Hibernating Rhinos Ltd  

Oren Eini l CEO l Mobile: + 972-52-548-6969

Office: +972-4-622-7811 l Fax: +972-153-4-622-7811

 

--

[Krzysztof Pajak]

Thanks,

But where can I find info about Include the dynamic parameters in the reduce definition ?

Regards

Krzysztof

[Oren Eini (Ayende Rahien)]

You don't, you include them in the group by, then you filter on them.