In this section, we will cover the basics of indexing data in Elasticsearch. Indexing is the process of adding data to Elasticsearch so that it can be searched and analyzed. We will explore how to create indices, add documents, and understand the structure of an indexed document.

1. Index: A collection of documents that have somewhat similar characteristics.
2. Document: A JSON object that is stored in an index.
3. Field: A key-value pair in a document.

To create an index in Elasticsearch, you can use the PUT request. Here is an example:

• PUT /my_first_index: This creates an index named my_first_index.
• settings: This section allows you to configure the index settings.
  • number_of_shards: The number of primary shards that the index should have.
  • number_of_replicas: The number of replica shards.

To add a document to an index, you use the POST or PUT request. Here is an example using POST:

• POST /my_first_index/_doc/: This adds a new document to the my_first_index index.
• The body of the request is the JSON document you want to index.

To retrieve a document, you use the GET request. Here is an example:

• GET /my_first_index/_doc/1: This retrieves the document with ID 1 from the my_first_index index.

Let's go through a practical example step-by-step:

1. Create an Index:

   PUT /blog
   {
     "settings": {
       "number_of_shards": 1,
       "number_of_replicas": 1
     }
   }
   

2. Add a Document:

   POST /blog/_doc/
   {
     "author": "Jane Doe",
     "title": "Elasticsearch Basics",
     "content": "This is an introductory post about Elasticsearch.",
     "publish_date": "2023-10-01"
   }
   

3. Retrieve the Document:

   GET /blog/_doc/1
   

1. Create an index named library.
2. Add a document to the library index with the following fields:
   • title: "Elasticsearch Guide"
   • author: "John Smith"
   • published_date: "2023-09-15"
   • content: "A comprehensive guide to Elasticsearch."

1. Create the Index:

   PUT /library
   {
     "settings": {
       "number_of_shards": 1,
       "number_of_replicas": 1
     }
   }
   

2. Add the Document:

   POST /library/_doc/
   {
     "title": "Elasticsearch Guide",
     "author": "John Smith",
     "published_date": "2023-09-15",
     "content": "A comprehensive guide to Elasticsearch."
   }
   

Retrieve the document you just added to the library index.

• Mistake: Forgetting to specify the index name in the URL.

  • Tip: Always ensure the index name is included in the URL when making requests.

• Mistake: Using incorrect HTTP methods (e.g., using GET instead of POST to add a document).

  • Tip: Familiarize yourself with the correct HTTP methods for each operation.

In this section, we learned how to create an index, add documents to it, and retrieve those documents. These are fundamental operations in Elasticsearch that form the basis for more advanced functionalities. In the next section, we will explore how to search for data within an index.