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Persian analyzer

The built-in persian analyzer can be applied to a text field using the following command:

PUT /persian-index
{
  "mappings": {
    "properties": {
      "content": {
        "type": "text",
        "analyzer": "persian"
      }
    }
  }
}

Stem exclusion

You can use stem_exclusion with this language analyzer using the following command:

PUT index_with_stem_exclusion_persian_analyzer
{
  "settings": {
    "analysis": {
      "analyzer": {
        "stem_exclusion_persian_analyzer": {
          "type": "persian",
          "stem_exclusion": ["حکومت", "تأیید"]
        }
      }
    }
  }
}

Persian analyzer internals

The persian analyzer is built using the following components:

  • Tokenizer: standard

  • Char filter: mapping

  • Token filters:

    • lowercase
    • decimal_digit
    • normalization (Arabic)
    • normalization (Persian)
    • keyword
    • stemmer (Norwegian)

Custom Persian analyzer

You can create a custom Persian analyzer using the following command:

PUT /persian-index
{
  "settings": {
    "analysis": {
      "filter": {
        "persian_stop": {
          "type": "stop",
          "stopwords": "_persian_"
        },
        "persian_keywords": {
          "type": "keyword_marker",
          "keywords": []
        }
      },
      "char_filter": {
        "null_width_replace_with_space": {
            "type":       "mapping",
            "mappings": [ "\\u200C=>\\u0020"] 
        }
      },
      "analyzer": {
        "persian_analyzer": {
          "type": "custom",
          "tokenizer": "standard",
          "char_filter": [ "null_width_replace_with_space" ],
          "filter": [
            "lowercase",
            "decimal_digit",
            "arabic_normalization",
            "persian_normalization",
            "persian_stop"
          ]
        }
      }
    }
  },
  "mappings": {
    "properties": {
      "content": {
        "type": "text",
        "analyzer": "persian_analyzer"
      }
    }
  }
}

Generated tokens

Use the following request to examine the tokens generated using the analyzer:

POST /persian-index/_analyze
{
  "field": "content",
  "text": "دانشجویان در دانشگاه‌های ایرانی تحصیل می‌کنند. شماره‌های آن‌ها ۱۲۳۴۵۶ است."
}

The response contains the generated tokens:

{
  "tokens": [
    {"token": "دانشجويان","start_offset": 0,"end_offset": 9,"type": "<ALPHANUM>","position": 0},
    {"token": "دانشگاه","start_offset": 13,"end_offset": 20,"type": "<ALPHANUM>","position": 2},
    {"token": "ايراني","start_offset": 25,"end_offset": 31,"type": "<ALPHANUM>","position": 4},
    {"token": "تحصيل","start_offset": 32,"end_offset": 37,"type": "<ALPHANUM>","position": 5},
    {"token": "شماره","start_offset": 47,"end_offset": 52,"type": "<ALPHANUM>","position": 8},
    {"token": "123456","start_offset": 63,"end_offset": 69,"type": "<NUM>","position": 12}
  ]
}
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