How to speed up Facet count (Big index) ??!!!!

[Aeroox Aeroox]

Hi folks,

I have a solr index with up to 50M documents. A document contain 62 fields
(docid, name, location....).

The facet count took 1 to 2 minutes with this params :

http://XXXX.../select/?q=solr&;
version=2.2&start=0&rows=0&facet=true&facet.limit=6&facet.mincount=1&mm=3<-1&facet.field=schoolname_hl&facet.method=fc

and here is how look my schoolname_hl in solr schema :

<field name="schoolname_hl" type="text_hl" indexed="true" stored="false"
multiValued="true"/>

text_hl is defined like this:

<fieldType name="text_hl" class="solr.TextField" sortMissingLast="true"
omitNorms="true">
      <analyzer type="index">
        <tokenizer class="solr.KeywordTokenizerFactory"/>
        <filter class="solr.ASCIIFoldingFilterFactory"/>
        <filter class="solr.StandardFilterFactory"/>
        <filter class="solr.SynonymFilterFactory" synonyms="synonyms.txt"
ignoreCase="true" expand="true"/>
        <filter class="solr.StopFilterFactory"
                ignoreCase="true"
                words="stopwords.txt"
                enablePositionIncrements="true"
                />
        <filter class="solr.TrimFilterFactory"/>
        <filter class="solr.LowerCaseFilterFactory"/>
        <filter class="solr.RemoveDuplicatesTokenFilterFactory"/>
      </analyzer>
      <analyzer type="query">
        <tokenizer class="solr.KeywordTokenizerFactory"/>
        <filter class="solr.ASCIIFoldingFilterFactory"/>
        <filter class="solr.StandardFilterFactory"/>
        <filter class="solr.SynonymFilterFactory" synonyms="synonyms.txt"
ignoreCase="true" expand="true"/>
        <filter class="solr.StopFilterFactory"
                ignoreCase="true"
                words="stopwords.txt"
                enablePositionIncrements="true"
        />
        <filter class="solr.TrimFilterFactory"/>
        <filter class="solr.LowerCaseFilterFactory"/>
        <filter class="solr.RemoveDuplicatesTokenFilterFactory"/>
      </analyzer>
</fieldType>


And my cache policy :

<filterCache class="solr.FastLRUCache"
                 size="4096"
                 initialSize="4096"
                 autowarmCount="4096"/>

    <queryResultCache class="solr.LRUCache"
                     size="5000"
                     initialSize="5000"
                     autowarmCount="5000"/>

    <documentCache class="solr.LRUCache"
                   size="512"
                   initialSize="512"
                   autowarmCount="0"/>


I'm doing something wrong?

How i can speed up the facet count process in my case ?

for the record :

* i'm using solr 1.4 (LUCENE_36)
* 64GB Ram (with 60GB allocated to java/tomcat6)

Thanks in advance.

With love from Paris