Keyword extraction in Elasticsearch can be achieved using various techniques, and one popular approach is using the ingest-attachment plugin along with the language processor to perform natural language processing (NLP) and extract keywords from text documents. This allows you to extract important terms and concepts from documents and index them separately for better search and analysis.

Here's a step-by-step guide on how to enable keyword extraction using the ingest-attachment plugin in Elasticsearch:

Step 1: Install the Ingest Attachment Plugin First, you need to install the ingest-attachment plugin in Elasticsearch. This plugin allows Elasticsearch to index and extract metadata from various types of attachments, including PDF, DOCX, PPTX, etc.

To install the plugin, you can use the Elasticsearch bin/elasticsearch-plugin command:

bash
bin/elasticsearch-plugin install ingest-attachment

Step 2: Create an Index with an Ingest Pipeline Next, you need to create an Elasticsearch index and define an ingest pipeline that uses the ingest-attachment processor for keyword extraction.

For example, using the Elasticsearch RESTful API, you can create an index and define the ingest pipeline:

json
PUT /my_index { "settings": { "number_of_shards": 1, "number_of_replicas": 0 }, "mappings": { "properties": { "content": { "type": "text" }, "keywords": { "type": "text" } } }, "pipelines": { "attachment": { "description": "Extract keywords from attachments", "processors": [ { "attachment": { "field": "content" } }, { "keyword": { "field": "attachment.content", "ignore_above": 256, "keywords": 10, "languages": ["English"] } } ] } } }

Step 3: Index Documents and Extract Keywords Now you can index your documents, and the ingest pipeline will automatically extract keywords from the document's content.

json
POST /my_index/_doc?pipeline=attachment { "content": "Your text content goes here. This is a sample document for keyword extraction." }

The extracted keywords will be stored in the keywords field of the indexed document.

Step 4: Search for Keywords You can now perform searches based on the extracted keywords to retrieve relevant documents.

For example, to search for documents containing a specific keyword, you can use a simple query like this:

json
GET /my_index/_search { "query": { "match": { "keywords": "sample" } } }

This will return documents that contain the keyword "sample" in their extracted keywords.

Keep in mind that the quality of keyword extraction heavily depends on the content and language of your documents. Additionally, you may need to fine-tune the ingest pipeline and use additional NLP techniques to improve keyword extraction accuracy for your specific use case.

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