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He is a versatile software engineer with experience in a wide variety of applications/services.He is enthusiastic about new projects, embracing new technologies, and getting to know people in the field of software.

Create DynamoDB tables with Node.js

On this post we will create Tables on a DynamoDB Database using node.js

Before getting started we need to have local dynamodb installed since we want to avoid any costs for dynamodb usage. There was a previous post on local dynamodb. In case you use docker you can find a local dynamodb image or you can create one on you own as described here.

Using local DynamoDB and node.js is extremely handy for debugging. Local dynamodb provides as with an web user interface on http://localhost:8000/shell. The local dynamodb shell is a javascript shell, therefore the actions for node.js can be issued straight to the DynamoDB shell.

The actions would be the same as described on the corresponding java tutorial. First step is to create a table with a hash key. In this case the email of the user would be the hash key.

var createUsers = function(callback) {

	var dynamodb = new AWS.DynamoDB();

	var params = {
	    TableName : "Users",
	    KeySchema: [       
	        { AttributeName: "email", KeyType: "HASH"}
	    ],
	    AttributeDefinitions: [       
	        { AttributeName: "email", AttributeType: "S" }
	    ],
	    ProvisionedThroughput: {       
	        ReadCapacityUnits: 5, 
	        WriteCapacityUnits: 5
		   }
		};

	dynamodb.createTable(params, callback);	
};

The next table will be called Logins. Logins should keep track each time the user logged in. To do so apart from using a hash key we will also use a range key for the date it occurred.

var createLogins = function(callback) {

	var dynamodb = new AWS.DynamoDB();

	var params = {
	    TableName : "Logins",
	    KeySchema: [       
	        { AttributeName: "email", KeyType: "HASH"},
	        { AttributeName: "timestamp", KeyType: "RANGE"}
		],
	    AttributeDefinitions: [       
	        { AttributeName: "email", AttributeType: "S" },
	        { AttributeName: "timestamp", AttributeType: "N" }
	    ],
	    ProvisionedThroughput: {       
	        ReadCapacityUnits: 5, 
	        WriteCapacityUnits: 5
		   }
		};

	dynamodb.createTable(params, callback);	
};

Next table is Supervisors. The hash key of Supervisor would be his name. A supervisor will work for a company. The company will be our global secondary index. Since the companies own more than one factories the field factory would be the range key.

var createSupervisors = function(callback) {

	var dynamodb = new AWS.DynamoDB();

	var params = {
	    TableName : "Supervisors",
	    KeySchema: [       
	        { AttributeName: "name", KeyType: "HASH"}
		],
	    AttributeDefinitions: [       
	        { AttributeName: "name", AttributeType: "S" },
	        { AttributeName: "company", AttributeType: "S" },
	        { AttributeName: "factory", AttributeType: "S" }    
	    ],
	    ProvisionedThroughput: {       
	        ReadCapacityUnits: 5, 
	        WriteCapacityUnits: 5
		   },
		GlobalSecondaryIndexes: [{
				IndexName: "FactoryIndex",
				KeySchema: [
				    {
				    	AttributeName: "company",
				    	KeyType: "HASH"
				    },
					{
						AttributeName: "factory",
						KeyType: "RANGE"
					}
				],
				Projection: {
					ProjectionType: "ALL"
				},
				ProvisionedThroughput: {
					ReadCapacityUnits: 1,
					WriteCapacityUnits: 1
				}
		    }]
	};

	dynamodb.createTable(params, callback);	
};

Next table would be the table Companies. The hash key would be the parent company and the range key the subsidiary company. Each company has a CEO. The CEO would be the range key for the local secondary index.

var createCompanies = function(callback) {

	var dynamodb = new AWS.DynamoDB();

	var params = {
	    TableName : "Companies",
	    KeySchema: [       
	        { AttributeName: "name", KeyType: "HASH"},
	        { AttributeName: "subsidiary", KeyType: "RANGE"}
		],
	    AttributeDefinitions: [       
	        { AttributeName: "name", AttributeType: "S" },
	        { AttributeName: "subsidiary", AttributeType: "S" },
	        { AttributeName: "ceo", AttributeType: "S" }    
	    ],
	    ProvisionedThroughput: {       
	        ReadCapacityUnits: 5, 
	        WriteCapacityUnits: 5
		   },
		LocalSecondaryIndexes: [{
				IndexName: "CeoIndex",
				KeySchema: [
				    {
				    	AttributeName: "name",
				    	KeyType: "HASH"
				    },
					{
						AttributeName: "ceo",
						KeyType: "RANGE"
					}
				],
				Projection: {
					ProjectionType: "ALL"
				}
		    }]
	};

	dynamodb.createTable(params, callback);	
};

You can find the source code on github.

Reference: Create DynamoDB tables with Node.js from our WCG partner Emmanouil Gkatziouras at the gkatzioura blog.

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