NGram with Elasticsearch

Setup a sandbox

Note: Even without the video, you can learn all the crucial details from the steps that are documented below

https://youtu.be/vinrUb8vab8youtu.be

1. Login to your cloud-box over ssh

2. Create a directory for running an elasticsearch sandbox:

   mkdir -p ~/dev/elasticsearch-sandbox

3. Step into the working directory:

   cd ~/dev/elasticsearch-sandbox

4. Create a docker-compose.yml file to install and run elasticsearch:

   ## Version Selection for compose file
   # https://docs.docker.com/compose/compose-file/#/versioning
   version: '2'
   services:
      es_v2:
       image: elasticsearch:2
       ports:
        - "9202:9200"
       volumes:
        - ./docker-entrypoint-es2-plugins.sh:/apps/docker-entrypoint-es2-plugins.sh
       entrypoint: /apps/docker-entrypoint-es2-plugins.sh

5. Create an entrypoint file named docker-entrypoint-es2-plugins.sh to install useful plugins:

   #!/bin/bash
   # setting up prerequisites
   
   # re-runs will give an error that is harmless:
   #   > ERROR: plugin directory /usr/share/elasticsearch/plugins/delete-by-query already exists.
   #   > To update the plugin, uninstall it first using 'remove delete-by-query' command
   #plugin install delete-by-query
   
   # https://github.com/mobz/elasticsearch-head/#running-as-a-plugin-of-elasticsearch
   plugin install mobz/elasticsearch-head
   
   # access it at /_plugin/elasticsearch-inquisitor/
   plugin install polyfractal/elasticsearch-inquisitor
   
   #exec /docker-entrypoint.sh elasticsearch
   exec elasticsearch -Des.insecure.allow.root=true

6. Make sure to change the permissions to execute sh files:

   chmod 744 *.sh

7. Start the service: docker-compose up

8. Open a browser to view the two plugins running on ES:

   1. esHead - http://your-cloud-box-ip:9202/_plugin/head/

   2. esInq - http://your-cloud-box-ip:9202/_plugin/elasticsearch-inquisitor/

Play Around

1. Use the Any Request tab in /_plugin/head/ to create an index with a custom analyzer for a 3 by 3 ngram:

   PUT testing_ngram_3_by_3
   {
     "settings": {
       "analysis": {
         "analyzer": {
           "ngram_3_by_3": {
             "tokenizer": "ngram_3_by_3"
           }
         },
         "tokenizer": {
             "ngram_3_by_3": {
             "type": "ngram",
             "min_gram": 3,
             "max_gram": 3,
             "token_chars": [
               "letter",
               "digit"
             ]
           }
         }
       }
     }
   }

2. Go to /_plugin/elasticsearch-inquisitor/#/analyzers to see the ngram_3_by_3 analyzer at the bottom of the page.

   • click the checkbox and then use the top most input field to see how the analyzer breaks down the input into tokens