ドキュメントによるCRUD操作

In the world of data, CRUD is a fundamental concept. It stands for Create, Read, Update, and Delete.

These are the four basic operations you perform on data in any system, including Elasticsearch. Mastering them is key to managing your search documents effectively.

Adding a new document to Elasticsearch is called indexing. You can index documents:

• By letting Elasticsearch generate a unique ID (using POST).
• By providing your own custom ID (using PUT).

The document content is sent as a JSON body.

Let's index a book document. We'll use PUT and specify books/_doc/101 to give it a custom ID of 101.

To fetch a document, you use the Get API. You just need to know its unique ID (_id) and the index it's in.

Elasticsearch will return the document's source (_source) along with metadata like its _index, _id, and _version.

Now, let's retrieve the book we just indexed using its ID.

One way to update a document is to completely replace it. You use the PUT method with the same document ID.

Be careful! Any fields missing from your new PUT request will be deleted from the original document.

Let's add a genre field to our book. Notice how we provide the full document again, including existing fields.

For small changes, fully replacing a document is inefficient. Elasticsearch provides the _update API for partial updates.

This allows you to send only the fields you want to change, making the operation faster and using less bandwidth. You use the POST method.

Let's update just the year field of our book using the _update API and the "doc" parameter. This merges the changes.

To permanently remove a document from your index, you use the Delete API. Simply specify the index and the document's ID.

Once deleted, the document is gone and cannot be retrieved.

You have a document with fields name, age, and city. You want to change only the city field to a new value. Which is the most efficient and recommended way to do this in Elasticsearch?

Great job! You've learned the essential CRUD operations for managing documents in Elasticsearch:

• Create (Index): Add new documents with PUT (custom ID) or POST (auto ID).
• Read (Get): Retrieve documents by ID using GET.
• Update: Replace documents entirely with PUT or perform efficient partial updates with POST /_update.
• Delete: Remove documents by ID using DELETE.

These operations form the backbone of interacting with your Elasticsearch data.