OpenSearch MinHash Plugin

Overview

MinHash Plugin provides b-bit MinHash algorithm for OpenSearch. Using a field type and a token filter provided by this plugin, you can add a minhash value to your document.

Version

Versions in Maven Repository

Issues/Questions

Please file an issue.

Installation

$ $OPENSEARCH_HOME/bin/opensearch-plugin install org.codelibs.opensearch:opensearch-minhash:1.1.0

Getting Started

Add MinHash Analyzer

First, you need to add a minhash analyzer when creating your index:

$ curl -XPUT 'localhost:9200/my_index' -d '{
  "index":{
    "analysis":{
      "analyzer":{
        "minhash_analyzer":{
          "type":"custom",
          "tokenizer":"standard",
          "filter":["minhash"]
        }
      }
    }
  }
}'

You are free to change tokenizer/char_filter/filter settings, but the minhash filter needs to be added as a last filter.

Add MinHash field

Put a minhash field into an index mapping:

$ curl -XPUT "localhost:9200/my_index/_mapping" -d '{
  "properties":{
    "message":{
      "type":"string",
      "copy_to":"minhash_value"
    },
    "minhash_value":{
      "type":"minhash",
      "store":true,
      "minhash_analyzer":"minhash_analyzer"
    }
  }
}'

The field type of minhash is of binary type. The above example calculates a minhash value of the message field and stores it in the minhash_value field.

Get MinHash Value

Add the following document:

$ curl -XPUT "localhost:9200/my_index/_doc/1" -d '{
  "message":"Fess is Java based full text search server provided as OSS product."
}'

The minhash value is calculated automatically when adding the document. You can check it as below:

$ curl -XGET "localhost:9200/my_index/_doc/1?pretty&stored_fields=minhash_value,_source"

The response is:

{
  "_index" : "my_index",
  "_type" : "_doc",
  "_id" : "1",
  "_version" : 1,
  "found" : true,
  "_source":{
      "message":"Fess is Java based full text search server provided as OSS product."
    },
  "fields" : {
    "minhash_value" : [ "KV5rsUfZpcZdVojpG8mHLA==" ]
  }
}

References

Change the number of bits and hashes

To change the number of bits and hashes, set them to a token filter setting:

$ curl -XPUT 'localhost:9200/my_index' -d '{
  "index":{
    "analysis":{
      "analyzer":{
        "minhash_analyzer":{
          "type":"custom",
          "tokenizer":"standard",
          "filter":["my_minhash"]
        }
      }
    },
    "filter":{
      "my_minhash":{
        "type":"minhash",
        "seed":100,
        "bit":2,
        "size":32
      }
    }
  }
}'

The above allows to set the number of bits to 2, the number of hashes to 32 and the seed of hash to 100.