[Dovecot] solr substring schema.xml

[Daniel Miller]

I'm trying a modified schema.xml with solr - it appears I now have 
substring searches!

I took the schema.xml file shipped with Dovecot, and modified the text 
field definition to be:

<fieldType name="text" class="solr.TextField" positionIncrementGap="100">
<analyzer type="index">
<tokenizer class="solr.WhitespaceTokenizerFactory"/>
<filter class="solr.StopFilterFactory" ignoreCase="true" 
words="stopwords.txt"/>
<filter class="solr.WordDelimiterFilterFactory" generateWordParts="1" 
generateNumberParts="1" catenateWords="1" catenateNumbers="1" 
catenateAll="0"/>
<filter class="solr.LowerCaseFilterFactory"/>
<filter class="solr.SnowballPorterFilterFactory" protected="protwords.txt"/>
<filter class="solr.NGramFilterFactory" minGramSize="3" maxGramSize="15"/>
<filter class="solr.RemoveDuplicatesTokenFilterFactory"/>
</analyzer>
<analyzer type="query">
<tokenizer class="solr.WhitespaceTokenizerFactory"/>
<filter class="solr.SynonymFilterFactory" synonyms="synonyms.txt" 
ignoreCase="true" expand="true"/>
<filter class="solr.StopFilterFactory" ignoreCase="true" 
words="stopwords.txt"/>
<filter class="solr.WordDelimiterFilterFactory" generateWordParts="1" 
generateNumberParts="1" catenateWords="0" catenateNumbers="0" 
catenateAll="0"/>
<filter class="solr.LowerCaseFilterFactory"/>
<filter class="solr.SnowballPorterFilterFactory" protected="protwords.txt"/>
<filter class="solr.RemoveDuplicatesTokenFilterFactory"/>
</analyzer>
</fieldType>

Changing to the new "SnowballPorter" instead of the deprecated 
"EnglishPorter" filters is probably minor - the magic is the 
"NGramFilterFactory".  3 & 15 seemed reasonable defaults for the min/max 
size to search on.
-- 
Daniel