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Reverse token filter

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Reverse token filter

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Reverses each token in a stream. For example, you can use the reverse filter to change cat to tac.

Reversed tokens are useful for suffix-based searches, such as finding words that end in -ion or searching file names by their extension.

This filter uses Lucene’s ReverseStringFilter.

Example

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The following analyze API request uses the reverse filter to reverse each token in quick fox jumps:

response = client.indices.analyze(
  body: {
    tokenizer: 'standard',
    filter: [
      'reverse'
    ],
    text: 'quick fox jumps'
  }
)
puts response

GET _analyze
{
  "tokenizer" : "standard",
  "filter" : ["reverse"],
  "text" : "quick fox jumps"
}

The filter produces the following tokens:

[ kciuq, xof, spmuj ]

Add to an analyzer

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The following create index API request uses the reverse filter to configure a new custom analyzer.

response = client.indices.create(
  index: 'reverse_example',
  body: {
    settings: {
      analysis: {
        analyzer: {
          whitespace_reverse: {
            tokenizer: 'whitespace',
            filter: [
              'reverse'
            ]
          }
        }
      }
    }
  }
)
puts response

PUT reverse_example
{
  "settings" : {
    "analysis" : {
      "analyzer" : {
        "whitespace_reverse" : {
          "tokenizer" : "whitespace",
          "filter" : ["reverse"]
        }
      }
    }
  }
}

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