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Stemmer override token filter

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Stemmer override token filter

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Overrides stemming algorithms, by applying a custom mapping, then protecting these terms from being modified by stemmers. Must be placed before any stemming filters.

Rules are mappings in the form of token1[, ..., tokenN] => override.

Setting	Description
`rules`	A list of mapping rules to use.
`rules_path`	A path (either relative to `config` location, or absolute) to a list of mappings.

Here is an example:

response = client.indices.create(
  index: 'my-index-000001',
  body: {
    settings: {
      analysis: {
        analyzer: {
          my_analyzer: {
            tokenizer: 'standard',
            filter: [
              'lowercase',
              'custom_stems',
              'porter_stem'
            ]
          }
        },
        filter: {
          custom_stems: {
            type: 'stemmer_override',
            rules_path: 'analysis/stemmer_override.txt'
          }
        }
      }
    }
  }
)
puts response

PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "standard",
          "filter": [ "lowercase", "custom_stems", "porter_stem" ]
        }
      },
      "filter": {
        "custom_stems": {
          "type": "stemmer_override",
          "rules_path": "analysis/stemmer_override.txt"
        }
      }
    }
  }
}

Where the file looks like:

running, runs => run

stemmer => stemmer

You can also define the overrides rules inline:

response = client.indices.create(
  index: 'my-index-000001',
  body: {
    settings: {
      analysis: {
        analyzer: {
          my_analyzer: {
            tokenizer: 'standard',
            filter: [
              'lowercase',
              'custom_stems',
              'porter_stem'
            ]
          }
        },
        filter: {
          custom_stems: {
            type: 'stemmer_override',
            rules: [
              'running, runs => run',
              'stemmer => stemmer'
            ]
          }
        }
      }
    }
  }
)
puts response

PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "standard",
          "filter": [ "lowercase", "custom_stems", "porter_stem" ]
        }
      },
      "filter": {
        "custom_stems": {
          "type": "stemmer_override",
          "rules": [
            "running, runs => run",
            "stemmer => stemmer"
          ]
        }
      }
    }
  }
}

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