Solr spellcheck suggestions never returns german umlauts

Question

I am implementing the solr spellcheck for a german page, but I am not able to receive german umlauts from there.

/spell?spellcheck=on&spellcheck.count=1&spellcheck.collate=true&spellcheck.q=wärme" it never returns umlauts:

How can I achieve this? Here is my solrconfig.xml snippet for the spellcheck:

<searchComponent name="spellcheck" class="solr.SpellCheckComponent">

    <str name="queryAnalyzerFieldType">text_general</str>

    <!-- Multiple "Spell Checkers" can be declared and used by this
         component
      -->

    <!-- a spellchecker built from a field of the main index -->
    <lst name="spellchecker">
      <str name="name">default</str>
      <str name="field">autocomplete</str>
      <str name="classname">solr.DirectSolrSpellChecker</str>
      <!-- the spellcheck distance measure used, the default is the internal levenshtein -->
      <str name="distanceMeasure">internal</str>
      <!-- minimum accuracy needed to be considered a valid spellcheck suggestion -->
      <float name="accuracy">0.25</float>
      <!-- the maximum #edits we consider when enumerating terms: can be 1 or 2 -->
      <int name="maxEdits">2</int>
      <!-- the minimum shared prefix when enumerating terms -->
      <int name="minPrefix">1</int>
      <!-- maximum number of inspections per result. -->
      <int name="maxInspections">10</int>
      <!-- minimum length of a query term to be considered for correction -->
      <int name="minQueryLength">1</int>
      <!-- maximum threshold of documents a query term can appear to be considered for correction -->
      <float name="maxQueryFrequency">0.01</float>
      <!-- uncomment this to require suggestions to occur in 1% of the documents
        <float name="thresholdTokenFrequency">.01</float>
      -->
    </lst>

    <!-- a spellchecker that can break or combine words.  See "/spell" handler below for usage -->
    <!--
    <lst name="spellchecker">
      <str name="name">wordbreak</str>
      <str name="classname">solr.WordBreakSolrSpellChecker</str>
      <str name="field">name</str>
      <str name="combineWords">true</str>
      <str name="breakWords">true</str>
      <int name="maxChanges">10</int>
    </lst>
    -->
  </searchComponent>

  <!-- A request handler for demonstrating the spellcheck component.

       NOTE: This is purely as an example.  The whole purpose of the
       SpellCheckComponent is to hook it into the request handler that
       handles your normal user queries so that a separate request is
       not needed to get suggestions.

       IN OTHER WORDS, THERE IS REALLY GOOD CHANCE THE SETUP BELOW IS
       NOT WHAT YOU WANT FOR YOUR PRODUCTION SYSTEM!

       See http://wiki.apache.org/solr/SpellCheckComponent for details
       on the request parameters.
    -->
  <requestHandler name="/spell" class="solr.SearchHandler" startup="lazy">
    <lst name="defaults">
      <!-- Solr will use suggestions from both the 'default' spellchecker
           and from the 'wordbreak' spellchecker and combine them.
           collations (re-written queries) can include a combination of
           corrections from both spellcheckers -->
      <str name="spellcheck.dictionary">default</str>
      <str name="spellcheck">on</str>
      <str name="spellcheck.extendedResults">true</str>
      <str name="spellcheck.count">10</str>
      <str name="spellcheck.alternativeTermCount">5</str>
      <str name="spellcheck.maxResultsForSuggest">5</str>
      <str name="spellcheck.collate">false</str>
      <str name="spellcheck.collateExtendedResults">true</str>
      <str name="spellcheck.maxCollationTries">10</str>
      <str name="spellcheck.maxCollations">5</str>
      <str name="spellcheck.alternativeTermCount">5</str>
    </lst>
    <arr name="last-components">
      <str>spellch<searchComponent name="spellcheck" class="solr.SpellCheckComponent">

    <str name="queryAnalyzerFieldType">text_general</str>

    <!-- Multiple "Spell Checkers" can be declared and used by this
         component
      -->

    <!-- a spellchecker built from a field of the main index -->
    <lst name="spellchecker">
      <str name="name">default</str>
      <str name="field">autocomplete</str>
      <str name="classname">solr.DirectSolrSpellChecker</str>
      <!-- the spellcheck distance measure used, the default is the internal levenshtein -->
      <str name="distanceMeasure">internal</str>
      <!-- minimum accuracy needed to be considered a valid spellcheck suggestion -->
      <float name="accuracy">0.25</float>
      <!-- the maximum #edits we consider when enumerating terms: can be 1 or 2 -->
      <int name="maxEdits">2</int>
      <!-- the minimum shared prefix when enumerating terms -->
      <int name="minPrefix">1</int>
      <!-- maximum number of inspections per result. -->
      <int name="maxInspections">10</int>
      <!-- minimum length of a query term to be considered for correction -->
      <int name="minQueryLength">1</int>
      <!-- maximum threshold of documents a query term can appear to be considered for correction -->
      <float name="maxQueryFrequency">0.01</float>
      <!-- uncomment this to require suggestions to occur in 1% of the documents
        <float name="thresholdTokenFrequency">.01</float>
      -->
    </lst>

    <!-- a spellchecker that can break or combine words.  See "/spell" handler below for usage -->
    <!--
    <lst name="spellchecker">
      <str name="name">wordbreak</str>
      <str name="classname">solr.WordBreakSolrSpellChecker</str>
      <str name="field">name</str>
      <str name="combineWords">true</str>
      <str name="breakWords">true</str>
      <int name="maxChanges">10</int>
    </lst>
    -->
  </searchComponent>

  <!-- A request handler for demonstrating the spellcheck component.

       NOTE: This is purely as an example.  The whole purpose of the
       SpellCheckComponent is to hook it into the request handler that
       handles your normal user queries so that a separate request is
       not needed to get suggestions.

       IN OTHER WORDS, THERE IS REALLY GOOD CHANCE THE SETUP BELOW IS
       NOT WHAT YOU WANT FOR YOUR PRODUCTION SYSTEM!

       See http://wiki.apache.org/solr/SpellCheckComponent for details
       on the request parameters.
    -->
  <requestHandler name="/spell" class="solr.SearchHandler" startup="lazy">
    <lst name="defaults">
      <!-- Solr will use suggestions from both the 'default' spellchecker
           and from the 'wordbreak' spellchecker and combine them.
           collations (re-written queries) can include a combination of
           corrections from both spellcheckers -->
      <str name="spellcheck.dictionary">default</str>
      <str name="spellcheck">on</str>
      <str name="spellcheck.extendedResults">true</str>
      <str name="spellcheck.count">10</str>
      <str name="spellcheck.alternativeTermCount">5</str>
      <str name="spellcheck.maxResultsForSuggest">5</str>
      <str name="spellcheck.collate">false</str>
      <str name="spellcheck.collateExtendedResults">true</str>
      <str name="spellcheck.maxCollationTries">10</str>
      <str name="spellcheck.maxCollations">5</str>
      <str name="spellcheck.alternativeTermCount">5</str>
    </lst>
    <arr name="last-components">
      <str>spellcheck</str>
    </arr>
  </requestHandler>

Answer 1

The DirectSolrSpellChecker uses the terms directly from the index - which means that any analysis happening to the terms before they're stored will be reflected in the suggestions returned.

Your field type replaces umlauts with their non-umlauted version, and that's the tokens being returned. You want as little analysis as possible to take place for suggestion fields, depending in your requirement for how the suggestions should work.

When choosing a field to query for this spell checker, you want one which has relatively little analysis performed on it (particularly analysis such as stemming).