Develop By Example – Creating schemas and collections using Node.js

In a previous post we explained how to connect to a MySQL server configured as a document store using the new MySQL Connector/Node.js. In this post we are going to explain how to create a schema, create a collection and add documents to the collection.

Creating a new schema is very easy; the following code demonstrates how to do it:

In the previous code example we created a connection and then used the XSession object to create a schema, finally we closed the connection.

The first line of code loads the Connector/Node.js client module, mysqlx. We then call its getSession() method to get the object that we are going to use to create the schema. We then call the createSchema method to create our schema; once the schema is created we call the session object’s close method to close our connection.

But, what will happen if we try to create a schema that already exists? An error will be thrown.

To avoid that situation we can verify if the schema exists before trying to create it.

In the previous code, before trying to create the schema we call the session object’s getSchema method. The object (schema) returned represents the schema we want to create, we then call its existsInDatabase method which will return false if the schema does not exist in the server or true otherwise. The following lines of code attempt to create the schema. The program notifies the user if the schema is created successfully, or if the schema already exists. Then it closes the session.

Now that we know how to create a schema and verify if it already exists in the database, it is time to work with collections. When creating a collection, we need to know which schema object it will belong to. This can be a new schema, or an existing one. If we try to create the collection in a schema where that collection is already present, the program returns an error. The following example demonstrates how to check if a collection already exists before creating it.

In the previous code, the first lines are the same for the code to verify if a schema exists if not it is created. Then we call the schema object’s getCollection method which returns an object that represents the collection (coll) we want to create. As we did for the schema object, we call the coll object’s existsInDatabase method. If the collection does not exist, it is created by calling the schema object’s createCollection method and we receive a confirmation message. If the collection already exists we are notified of the fact. Finally, the session is closed.

To add new documents to a collection we need to use a JSON notation for the document to create. In the following code, we are going to demonstrate how to add a document to a collection, bear in mind that in the code we assume that a schema and a collection already exist in the server.

In the previous code to add a new document, first, we get the objects that represent the schema (schema) and the collection (coll) that we want to work with. Then we created an object using JSON (newDoc). To add the document to the collection we call the coll object’s add method followed by the execute method, once the execute method has finished we receive an object (added) that contains information about the document added. By calling the added object’s getAffectedItemsCount method we know if the document was added.

In the next blog post, we are going to explain in more detail how to work with collections.
See you then.

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