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Pattern Analyzer

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Pattern Analyzer

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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:

`lowercase`	Should terms be lowercased or not. Defaults to `true`.
`pattern`	The regular expression pattern, defaults to `\W+`.
`flags`	The regular expression flags.
`stopwords`	A list of stopwords to initialize the stop filter with. Defaults to an empty stopword list Check Stop Analyzer for more details.

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

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

Whitespace tokenizer

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DELETE test

PUT /test
{
  "settings": {
    "analysis": {
      "analyzer": {
        "whitespace": {
          "type": "pattern",
          "pattern": "\\s+"
        }
      }
    }
  }
}

GET /test/_analyze?analyzer=whitespace&text=foo,bar baz

# "foo,bar", "baz"

Non-word character tokenizer

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DELETE test

PUT /test
{
  "settings": {
    "analysis": {
      "analyzer": {
        "nonword": {
          "type": "pattern",
          "pattern": "[^\\w]+" 
        }
      }
    }
  }
}

GET /test/_analyze?analyzer=nonword&text=foo,bar baz
# "foo,bar baz" becomes "foo", "bar", "baz"

GET /test/_analyze?analyzer=nonword&text=type_1-type_4
# "type_1","type_4"

CamelCase tokenizer

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DELETE test

PUT /test?pretty=1
{
  "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}]])"
        }
      }
    }
  }
}

GET /test/_analyze?analyzer=camel&text=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
  )

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