Interacting with Elasticsearch via REST API

Elasticsearch is a powerful tool for managing and analyzing data, offering a RESTful API that allows developers to interact with it using simple HTTP requests.

This API is built on the principles of Representational State Transfer (REST) making it accessible and intuitive for developers of all levels of expertise. In this article, We will learn about the How to Interacting with Elasticsearch via REST API with the help of examples in detail.

Understanding Elasticsearch REST API

• The Elasticsearch REST API is based on the principles of Representational State Transfer (REST) and allows us to perform CRUD (Create, Read, Update, Delete) operations on our Elasticsearch cluster using HTTP methods such as GET, POST, PUT, and DELETE.
  
• The REST API provides a simple and intuitive interface for interacting with Elasticsearch and making it accessible to developers of all skill levels.

Basic Concepts of Elasticsearch REST API

Before we perform the examples of interacting with Elasticsearch via its REST API, let's cover some basic concepts:

• Index: In Elasticsearch an index is like a big container or folder where we store similar types of information. Just like we might have a folder for photos another for documents and so on but in Elasticsearch, we have an index for different kinds of data.
  
• Document: In Elasticsearch the document is like a single piece of information. suppose we have a file on our computer that contains details about a specific thing like a customer's name, address and phone number. In Elasticsearch, this file would be called a document. It is a way to store and organize information so that we can easily find and retrieve it later.
  
• Query: In Elasticsearch a query is like asking a question to find specific information. We can use a query in Elasticsearch to find documents that match certain criteria. For example, we could ask Elasticsearch to find all products with a price less than $50 or all customers who live in a certain city.
  
• Mapping: Mapping as the instruction manual for Elasticsearch. It tells Elasticsearch how to understand and organize the data within each document. It specifies things like what type of data each field contains (like text, numbers, dates), and how it should be stored and searched.

How it Works

• When we want to do something with Elasticsearch, like search for information or add new data, we send it a request using the appropriate HTTP method (GET, POST, PUT, DELETE) along with the URL that specifies what we want to do.
  
• For example, if we want to search for all documents containing the word "apple" in the "Product Catalog" index, we would send a GET request to something like http://your-elasticsearch-server/product-catalog/_search?q=apple.

Examples of Interacting with Elasticsearch

To understand the Interacting with Elasticsearch in well manner. We will consider below sample documents to perform operations and queries for better understanding.

[
 {
 "_id": 1,
 "name": "Elasticsearch Beginner's Guide",
 "price": 29.99,
 "category": "Books"
 },
 {
 "_id": 2,
 "name": "Learning Elasticsearch",
 "price": 39.99,
 "category": "Books"
 },
 {
 "_id": 3,
 "name": "Mastering Elasticsearch",
 "price": 49.99,
 "category": "Books"
 },
 {
 "_id": 4,
 "name": "Elasticsearch in Action",
 "price": 34.99,
 "category": "Books"
 },
 {
 "_id": 5,
 "name": "Advanced Elasticsearch Techniques",
 "price": 44.99,
 "category": "Books"
 },
 {
 "_id": 6,
 "name": "The Definitive Guide to Elasticsearch",
 "price": 59.99,
 "category": "Books"
 }
]

1. Indexing Documents

Suppose we have to Add a new book to the library.

POST /products/_doc/1
{
 "name": "Elasticsearch Beginner's Guide",
 "price": 29.99,
 "category": "Books"
}

Response:

{
 "result": "created",
 "_index": "products",
 "_id": "1",
 "_version": 1,
 "_shards": {
 "total": 2,
 "successful": 1,
 "failed": 0
 },
 "_seq_no": 0,
 "_primary_term": 1
}

Use the POST method to send the new book's details to Elasticsearch, specifying the index name and unique ID for the document.

2. Searching Documents

Suppose we have to Find all books in the library with "Elasticsearch" in their title.

GET /products/_search
{
 "query": {
 "match": {
 "name": "Elasticsearch"
 }
 }
}

Response:

{
 "took": 5,
 "timed_out": false,
 "_shards": {
 "total": 5,
 "successful": 5,
 "skipped": 0,
 "failed": 0
 },
 "hits": {
 "total": {
 "value": 1,
 "relation": "eq"
 },
 "max_score": 0.15342641,
 "hits": [
 {
 "_index": "products",
 "_id": "1",
 "_score": 0.15342641,
 "_source": {
 "name": "Elasticsearch Beginner's Guide",
 "price": 29.99,
 "category": "Books"
 }
 }
 ]
 }
 }

Use the GET method to search the index for documents where the "name" field matches the term "Elasticsearch".

3. Updating Documents

Suppose we have to update the price of a book in the library.

POST /products/_update/1
{
 "doc": {
 "price": 39.99
 }
}

Response:

{
 "_index": "products",
 "_id": "1",
 "_version": 2,
 "_shards": {
 "total": 2,
 "successful": 1,
 "failed": 0
 },
 "_seq_no": 1,
 "_primary_term": 1
}

Use the POST method to update the price of the book by specifying its ID and the new price

4. Deleting Documents

Suppose we have to Remove a book from the library.

DELETE /products/_doc/1

Response:

{
 "_index": "products",
 "_id": "1",
 "_version": 3,
 "result": "deleted",
 "_shards": {
 "total": 2,
 "successful": 1,
 "failed": 0
 },
 "_seq_no": 2,
 "_primary_term": 1
}

Use the DELETE method to delete the document by specifying its ID.

Conclusion

Overall, the Elasticsearch REST API provides a straightforward and effective means of interacting with Elasticsearch and allowing developers to manage data with ease. By understanding the fundamental concepts of indexes, documents, queries, and mappings, developers can take help from the full potential of Elasticsearch for their projects. With examples defining common operations like indexing, searching, updating, and deleting documents, this guide has provided a solid foundation for working with Elasticsearch's REST API