MinHash Plugin provides b-bit MinHash algorithm for Elasticsearch. Using a field type and a token filter provided by this plugin, you can add a minhash value to your document.
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$ $ES_HOME/bin/elasticsearch-plugin install org.codelibs:elasticsearch-minhash:7.14.0
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.
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.
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==" ]
}
}
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.