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elasticsearch - guide - Pattern Analyzer

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Original source (www.elasticsearch.org)
Tags: elasticsearch pattern-analyzer analysis
Clipped on: 2012-11-01

An analyzer of type pattern that can flexibly separate text into terms via a regular expression. Accepts the following settings:

The following are settings that can be set for a pattern analyzer type:

Setting Description
lowercaseShould terms be lowercased or not. Defaults to true.
patternThe regular expression pattern, defaults to \W+.
flagsThe regular expression flags.

IMPORTANT: The regular expression should match the token separators, not the tokens themselves.

Flags should be pipe-separated, eg "CASE_INSENSITIVE|COMMENTS". Check Java Pattern API for more details about flags options.

Pattern Analyzer Examples

In order to try out these examples, you should delete the test index before running each example:

    curl -XDELETE localhost:9200/test

Whitespace tokenizer

    curl -XPUT 'localhost:9200/test' -d '
    {
        "settings":{
            "analysis": {
                "analyzer": {
                    "whitespace":{
                        "type": "pattern",
                        "pattern":"\\s+"
                    }
                }
            }
        }
    }'


    curl
'localhost:9200/test/_analyze?pretty=1&analyzer=whitespace' -d 'foo,bar baz'
   
# "foo,bar", "baz"

Non-word character tokenizer


    curl
-XPUT 'localhost:9200/test' -d '
    {
        "settings":{
            "analysis": {
                "analyzer": {
                    "nonword":{
                        "type": "pattern",
                        "pattern":"[^\\w]+"
                    }
                }
            }
        }
    }'


    curl
'localhost:9200/test/_analyze?pretty=1&analyzer=nonword' -d 'foo,bar baz'
   
# "foo,bar baz" becomes "foo", "bar", "baz"

    curl
'localhost:9200/test/_analyze?pretty=1&analyzer=nonword' -d 'type_1-type_4'
   
# "type_1","type_4"

CamelCase tokenizer


    curl
-XPUT 'localhost:9200/test?pretty=1' -d '
    {
        "settings":{
            "analysis": {
                "analyzer": {
                    "camel":{
                        "type": "pattern",
                        "pattern":"([^\\p{L}\\d]+)|(?<=\\D)(?=\\d)|(?<=\\d)(?=\\D)|(?<=[\\p{L}&&[^\\p{Lu}]])(?=\\p{Lu})|(?<=\\p{Lu})(?=\\p{Lu}[\\p{L}&&[^\\p{Lu}]])"
                    }
                }
            }
        }
    }'


    curl
'localhost:9200/test/_analyze?pretty=1&analyzer=camel' -d '
        MooseX::FTPClass2_beta
    '

   
# "moose","x","ftp","class","2","beta"

The regex above is easier to understand as:


     
([^\\p{L}\\d]+)                 # swallow non letters and numbers,
   
| (?<=\\D)(?=\\d)                 # or non-number followed by number,
   
| (?<=\\d)(?=\\D)                 # or number followed by non-number,
   
| (?<=[ \\p{L} && [^\\p{Lu}]])    # or lower case
     
(?=\\p{Lu})                     #   followed by upper case,
   
| (?<=\\p{Lu})                    # or upper case
     
(?=\\p{Lu}                      #   followed by upper case
       
[\\p{L}&&[^\\p{Lu}]]          #   then lower case
     
)