C# (CSharp) Lucene.Net.Analysis.Pattern Namespace

 <fieldType name="text_ptncapturegroup" class="solr.TextField" positionIncrementGap="100"> <analyzer> <tokenizer class="solr.KeywordTokenizerFactory"/> <filter class="solr.PatternCaptureGroupFilterFactory" pattern="([^a-z])" preserve_original="true"/> </analyzer> </fieldType>

For example, a pattern like:

"(https?://([a-zA-Z\-_0-9.]+))"

when matched against the string "http://www.foo.com/index" would return the tokens "https://www.foo.com" and "www.foo.com".

If none of the patterns match, or if preserveOriginal is true, the original token will be preserved.

Each pattern is matched as often as it can be, so the pattern "(...)", when matched against "abcdefghi" would produce ["abc","def","ghi"]

A camelCaseFilter could be written as:

"([A-Z]{2,})",
"(?<![A-Z])([A-Z][a-z]+)",
"(?:^|\\b|(?<=[0-9_])|(?<=[A-Z]{2}))([a-z]+)",
"([0-9]+)"

plus if #preserveOriginal is true, it would also return "camelCaseFilter

ex1) source="aa  bb aa bb", pattern="(aa)\\s+(bb)" replacement="$1#$2"
output="aa#bb aa#bb"

ex2) source="aa123bb", pattern="(aa)\\d+(bb)" replacement="$1 $2"
output="aa bb"
and you want to search bb and highlight it, you will get
highlight snippet="aa1<em>23bb</em>"

 <fieldType name="text_ptnreplace" class="solr.TextField" positionIncrementGap="100"> <analyzer> <charFilter class="solr.PatternReplaceCharFilterFactory"  pattern="([^a-z])" replacement=""/> <tokenizer class="solr.KeywordTokenizerFactory"/> </analyzer> </fieldType>

Note: Depending on the input and the pattern used and the input TokenStream, this TokenFilter may produce Tokens whose text is the empty string.

 <fieldType name="text_ptnreplace" class="solr.TextField" positionIncrementGap="100"> <analyzer> <tokenizer class="solr.KeywordTokenizerFactory"/> <filter class="solr.PatternReplaceFilterFactory" pattern="([^a-z])" replacement="" replace="all"/> </analyzer> </fieldType>

• "pattern" is the regular expression.
• "group" says which group to extract into tokens.

group=-1 (the default) is equivalent to "split". In this case, the tokens will be equivalent to the output from (without empty tokens): String#split(java.lang.String)

Using group >= 0 selects the matching group as the token. For example, if you have:

 pattern = \'([^\']+)\' group = 0 input = aaa 'bbb' 'ccc' 

NOTE: This Tokenizer does not output tokens that are of zero length.

• "pattern" is the regular expression.
• "group" says which group to extract into tokens.

group=-1 (the default) is equivalent to "split". In this case, the tokens will be equivalent to the output from (without empty tokens): String#split(java.lang.String)

Using group >= 0 selects the matching group as the token. For example, if you have:

 pattern = \'([^\']+)\' group = 0 input = aaa 'bbb' 'ccc' 

NOTE: This Tokenizer does not output tokens that are of zero length.

 <fieldType name="text_ptn" class="solr.TextField" positionIncrementGap="100"> <analyzer> <tokenizer class="solr.PatternTokenizerFactory" pattern="\'([^\']+)\'" group="1"/> </analyzer> </fieldType>