elasticsearch-concatenate-token-filter

Elasticsearch plugin which only provides a TokenFilter that merges tokens in a token stream back into one. Taken from http://elasticsearch-users.115913.n3.nabble.com/Is-there-a-concatenation-filter-td3711094.html

ElasticSearch version support

This plugin is compatible with ES 5.6.5.

Build

To build .zip or .jar for this plugin, run following command and you should see generated files in /target

mvn clean install

Install

To install on your current ES node, use the plugin binary provided in the bin folder (on Ubuntu it should be under /usr/share/elasticsearch/bin)

bin/elasticsearch-plugin  install file:<path to generated zip>/elasticsearch-concatenate-5.6.5.zip

Usage

The plugin provides a token filter of type concatenate which has one parameter token_separator. Use it in your custom analyzers to merge tokenized strings back into one single token (usually after applying stemming or other token filters).

Arrays

When saving arrays of strings to a field, these are handled in elasticsearch as separate tokens, so this filter would collapse all the elements of the array into one, and usually you don't want that to happen. As a workaround you can set position_offset_gap on the field to a high number and pass the same number as the increment_gap parameter to the filter, which then only concatenates all tokens closer than this value.

Example

Given the custom analyzer (see https://www.elastic.co/guide/en/elasticsearch/guide/current/custom-analyzers.html):

{
  "analysis" : {
    "filter" : {
      "concatenate" : {
        "type" : "concatenate",
        "token_separator" : "_"
      },
      "custom_stop" : {
        "type": "stop",
        "stopwords": ["and", "is", "the"]
      }
    },
    "analyzer" : {
      "stop_concatenate" : {
        "filter" : [
          "custom_stop",
          "concatenate"
        ],
        "tokenizer" : "standard"
      }
    }
  }
}

the string:

"the fox jumped over the fence"

would be analyzed as:

"fox_jumped_over_fence"