Get distinct property values using Search Server?

Question

I want to get all content authors for the search query results. I'm using following query:

<QueryPacket xmlns="urn:Microsoft.Search.Query">
  <Query>
      <SupportedFormats>
        <Format>urn:Microsoft.Search.Response.Document.Document</Format>
      </SupportedFormats>
    <Context>
       <QueryText type="FQL">forsiden</QueryText>
    </Context>
    <Properties>
      <Property name="Author" />
    </Properties>
    <TrimDuplicates onproperty="Author">true</TrimDuplicates>
  </Query>
 </QueryPacket>

But search results still contain duplicate values for Author property. Query is valid according to schema and TrimDuplicates part. What am I doing wrong?

EDIT

According to Mikael Svenson I'm trying to use such query:

<QueryPacket xmlns="urn:Microsoft.Search.Query">
  <Query>
    <SupportedFormats>
      <Format>urn:Microsoft.Search.Response.Document.Document</Format>
    </SupportedFormats>
    <Context>
      <QueryText type="FQL">us</QueryText>
    </Context>
    <Properties>
      <Property name="Author" />
    </Properties>
    <EnableStemming>true</EnableStemming>
    <EnableSpellCheck>false</EnableSpellCheck>
    <IncludeRelevantResults>false</IncludeRelevantResults>
    <Range>
      <Count>20</Count>
    </Range>
    <IncludeRefinementResults>
      <Refiners>
        <Refiner>author</Refiner>
      </Refiners>
    </IncludeRefinementResults>
  </Query>
</QueryPacket>

But resulting data set has no tables at all. I cant set ResultProvider to FASTSearch because when I do so, it throws exception:

The search request was unable to connect to the Search Service.

Maybe refiners cant be used with search server? But in features it is listed.

Answer 1

According to the schema documentation:

Query.TrimDuplicates.onproperty: Specifies the name of a managed property to use for duplicate result removal. The managed property MUST be of type integer.

Answer 2

It's quite easy. You have to think a bit different about the problem. In a user interface refiners give you distinct values with count, so get the refiners for Authors instead. No need for trimming.

The following query was created using the query tool at http://fastforsharepoint.codeplex.com/.

<QueryPacket Revision="1000">
  <Query>
    <Context>
      <QueryText language="en-US" type="FQL">forsiden</QueryText>
    </Context>
    <SupportedFormats Format="urn:Microsoft.Search.Response.Document.Document" />
    <ResultProvider>FASTSearch</ResultProvider>
    <Range>
      <StartAt>1</StartAt>
      <Count>0</Count>
    </Range>
    <EnableStemming>true</EnableStemming>
    <EnableSpellCheck>Off</EnableSpellCheck>
    <IncludeSpecialTermsResults>false</IncludeSpecialTermsResults>
    <IncludeRelevantResults>false</IncludeRelevantResults>
    <ImplicitAndBehavior>true</ImplicitAndBehavior>
    <IncludeRefinementResults>
      <Refiners>
        <Refiner>author</Refiner>
      </Refiners>
    </IncludeRefinementResults>
  </Query>
</QueryPacket>