Menu
AWS Cloud9
User Guide

Amazon DynamoDB Sample for AWS Cloud9

This sample enables you to set up an AWS Cloud9 development environment to work with Amazon DynamoDB.

DynamoDB is a fully managed NoSQL database service. You can use DynamoDB to create a database table that can store and retrieve any amount of data, and serve any level of request traffic. DynamoDB automatically spreads the data and traffic for the table over a sufficient number of servers to handle the request capacity specified and the amount of data stored, while maintaining consistent and fast performance. For more information, see Amazon DynamoDB on the AWS website.

Note

This sample assumes you already have the AWS Cloud9 IDE for your AWS Cloud9 development environment open in your web browser, and that you're using an AWS Cloud9 EC2 development environment that is connected to an Amazon EC2 instance running Amazon Linux. In you're using a different operating system or using an AWS Cloud9 SSH development environment, you might need to adapt this sample's instructions to correctly install and configure this sample's required tools. To create an environment, see Creating an Environment.

When you're using this sample, be sure you're signed in to AWS with the AWS account ID and name and password of the user you created or identified in Team Setup.

Creating this sample may result in charges to your AWS account. These include possible charges for services such as Amazon EC2 and DynamoDB. For more information, see Amazon EC2 Pricing and Amazon DynamoDB Pricing.

For information about additional AWS database offerings, see Amazon Relational Database Service (RDS), Amazon ElastiCache, and Amazon Redshift on the AWS website. See also AWS Database Migration Service on the AWS website.

Step 1: Install and Configure the AWS CLI in Your Environment

In this step, you use the AWS Cloud9 IDE to install and configure the AWS CLI in your environment so you can run commands to interact with DynamoDB. Then you use the AWS CLI to run a basic DynamoDB command to test your installation and configuration.

  1. To set up credentials management for the AWS CLI and to install the AWS CLI in your environment, follow Steps 1 and 2 in the AWS CLI Sample, and then return to this topic. If you already installed and configured the AWS CLI in your environment, you don't need to do it again.

  2. Test your AWS CLI installation and configuration by running the DynamoDB list-tables command from a terminal session in your environment to list your existing DynamoDB tables, if there are any. To start a new terminal session, on the menu bar, choose Windows, New Terminal.

    aws dynamodb list-tables

    If this command succeeds, it outputs a TableNames array containing a list of existing DynamoDB tables that you may already have. If you have no DynamoDB tables yet, the TableNames array will be empty.

    { "TableNames": [] }

    If you do have any DynamoDB tables, the TableNames array contains a list of the table names.

Step 2: Create a Table

In this step, you create a table in DynamoDB and specify the table's name, layout, simple primary key, and data throughput settings.

This sample table, named Weather, contains information about weather forecasts for a few cities in the United States. The table holds the following types of information (in DynamoDB, each piece of information is known as an attribute):

  • Required unique city ID (CityID)

  • Required forecast date (Date)

  • City name (City)

  • State name (State)

  • Forecast weather conditions (Conditions)

  • Forecast temperatures (Temperatures)

    • Forecast high, in degrees Fahrenheit (HighF)

    • Forecast low, in degrees Fahrenheit (LowF)

To create the table, in a terminal session in the AWS Cloud9 IDE, run the DynamoDB create-table command.

aws dynamodb create-table \ --table-name Weather \ --attribute-definitions \ AttributeName=CityID,AttributeType=N AttributeName=Date,AttributeType=S \ --key-schema \ AttributeName=CityID,KeyType=HASH AttributeName=Date,KeyType=RANGE \ --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

In this command:

  • --table-name represents the table name (Weather in this sample). Table names must be unique within each AWS Region in your AWS account.

  • --attribute-definitions represents the attributes that are used to uniquely identify the table items. Each of this table's items are uniquely identified by a combination of a numerical ID attribute and a Date attribute represented as an ISO-8601 formatted string.

  • --key-schema represents the table's key schema. This table has a composite primary key of CityID and Date. This means that each of the table items must have a CityID attribute value and a Date attribute value, but no two items in the table can have both the same CityID attribute value and Date attribute value.

  • --provisioned-throughput represents the table's read-write capacity. DynamoDB allows up to 5 strongly consistent reads per second for items up to 4 KB in size, or up to 5 eventually consistent reads per second for items up to 4 KB in size. DynamoDB also allows up to 5 writes per second for items up to 1 KB in size.

    Note

    Setting higher provisioned throughput may result in additional charges to your AWS account.

    For more information about this and other DynamoDB commands, see dynamodb in the AWS CLI Reference.

If this command succeeds, it displays summary information about the new table that is being created. To confirm the table is successfully created, run the DynamoDB describe-table command, specifying the table's name (--table-name).

aws dynamodb describe-table --table-name Weather

When the table is successfully created, the TableStatus value changes from CREATING to ACTIVE. Do not proceed past this step until the table is successfully created.

Step 3: Add an Item to the Table

In this step, you add an item to the table you just created.

  1. Create a file named weather-item.json with the following content. To create a new file, on the menu bar, choose File, New File. To save the file, choose File, Save.

    { "CityID": { "N": "1" }, "Date": { "S": "2017-04-12" }, "City": { "S": "Seattle" }, "State": { "S": "WA" }, "Conditions": { "S": "Rain" }, "Temperatures": { "M": { "HighF": { "N": "59" }, "LowF": { "N": "46" } } } }

    In this code, N represents an attribute value that is a number. S is a string attribute value. M is a map attribute, which is a set of attribute-value pairs. You must specify an attribute's data type whenever you work with items. For additional available attribute data types, see Data Types in the Amazon DynamoDB Developer Guide.

  2. Run the DynamoDB put-item command, specifying the table's name (--table-name) and the path to the JSON-formatted item (--item).

    aws dynamodb put-item \ --table-name Weather \ --item file://weather-item.json

    If the command succeeds, it runs without error, and no confirmation message is displayed.

  3. To confirm the table's current contents, run the DynamoDB scan command, specifying the table's name (--table-name).

    aws dynamodb scan --table-name Weather

    If the command succeeds, summary information about the table and the item you just added is displayed.

Step 4: Add Multiple Items to the Table

In this step, you add several more items to the Customers table.

  1. Create a file named more-weather-items.json with the following content.

    { "Weather": [ { "PutRequest": { "Item": { "CityID": { "N": "1" }, "Date": { "S": "2017-04-13" }, "City": { "S": "Seattle" }, "State": { "S": "WA" }, "Conditions": { "S": "Rain" }, "Temperatures": { "M": { "HighF": { "N": "52" }, "LowF": { "N": "43" } } } } } }, { "PutRequest": { "Item": { "CityID": { "N": "1" }, "Date": { "S": "2017-04-14" }, "City": { "S": "Seattle" }, "State": { "S": "WA" }, "Conditions": { "S": "Rain" }, "Temperatures": { "M": { "HighF": { "N": "49" }, "LowF": { "N": "43" } } } } } }, { "PutRequest": { "Item": { "CityID": { "N": "2" }, "Date": { "S": "2017-04-12" }, "City": { "S": "Portland" }, "State": { "S": "OR" }, "Conditions": { "S": "Thunderstorms" }, "Temperatures": { "M": { "HighF": { "N": "59" }, "LowF": { "N": "43" } } } } } }, { "PutRequest": { "Item": { "CityID": { "N": "2" }, "Date": { "S": "2017-04-13" }, "City": { "S": "Portland" }, "State": { "S": "OR" }, "Conditions": { "S": "Rain" }, "Temperatures": { "M": { "HighF": { "N": "51" }, "LowF": { "N": "41" } } } } } }, { "PutRequest": { "Item": { "CityID": { "N": "2" }, "Date": { "S": "2017-04-14" }, "City": { "S": "Portland" }, "State": { "S": "OR" }, "Conditions": { "S": "Rain Showers" }, "Temperatures": { "M": { "HighF": { "N": "49" }, "LowF": { "N": "39" } } } } } }, { "PutRequest": { "Item": { "CityID": { "N": "3" }, "Date": { "S": "2017-04-12" }, "City": { "S": "Portland" }, "State": { "S": "ME" }, "Conditions": { "S": "Rain" }, "Temperatures": { "M": { "HighF": { "N": "59" }, "LowF": { "N": "40" } } } } } }, { "PutRequest": { "Item": { "CityID": { "N": "3" }, "Date": { "S": "2017-04-13" }, "City": { "S": "Portland" }, "State": { "S": "ME" }, "Conditions": { "S": "Partly Sunny" }, "Temperatures": { "M": { "HighF": { "N": "54" }, "LowF": { "N": "37" } } } } } }, { "PutRequest": { "Item": { "CityID": { "N": "3" }, "Date": { "S": "2017-04-14" }, "City": { "S": "Portland" }, "State": { "S": "ME" }, "Conditions": { "S": "Mostly Sunny" }, "Temperatures": { "M": { "HighF": { "N": "53" }, "LowF": { "N": "37" } } } } } } ] }

    In this code, 8 Item objects define the 8 items to add to the table, similar to the single item defined in the previous step. However, when you run the DynamoDB batch-write-item command in the next step, you must provide a JSON-formatted object that includes each Item object in a containing PutRequest object. Then you must include those PutRequest objects in a parent array that has the same name as the table.

  2. Run the DynamoDB batch-write-item command, specifying the path to the JSON-formatted items to add (--request-items).

    aws dynamodb batch-write-item \ --request-items file://more-weather-items.json

    If the command succeeds, it displays the following message, confirming that the items were successfully added.

    { "UnprocessedItems": {} }
  3. To confirm the table's current contents, run the DynamoDB scan command again.

    aws dynamodb scan --table-name Weather

    If the command succeeds, 9 items are now displayed.

Step 5: Create a Global Secondary Index

Running the DynamoDB scan command to get information about items can be slow, especially as a table grows in size or if the type of information you want to get is complex. You can create one or more secondary indexes to speed things up and make getting information easier. In this step, you learn about two types of secondary indexes that DynamoDB supports to do just that. These are known as a local secondary index and a global secondary index. Then you create a global secondary index.

To understand these secondary index types, you first need to know about primary keys, which uniquely identify a table's items. DynamoDB supports a simple primary key or a composite primary key. A simple primary key has a single attribute, and that attribute value must be unique for each item in the table. This attribute is also known as a partition key (or a hash attribute), which DynamoDB can use to partition items for faster access. A table can also have a composite primary key, which contains two attributes. The first attribute is the partition key, and the second is a sort key (also known as a range attribute). In a table with a composite primary key, any two items can have the same partition key value, but they cannot also have the same sort key value. The Weather table has a composite primary key.

A local secondary index has the same partition key as the table itself, but this index type can have a different sort key. A global secondary index can have a partition key and a sort key that are both different from the table itself.

For example, you can already use the primary key to access Weather items by CityID. To access Weather items by State, you could create a local secondary index that has a partition key of CityID (it must be the same as the table itself) and a sort key of State. To access Weather items by City, you could create a global secondary index that has a partition key of City and a sort key of Date.

You can create local secondary indexes only while you are creating a table. Because the Weather table already exists, you cannot add any local secondary indexes to it. However, you can add global secondary indexes. Practice adding one now.

Note

Creating secondary indexes may result in additional charges to your AWS account.

  1. Create a file named weather-global-index.json with the following content.

    [ { "Create": { "IndexName": "weather-global-index", "KeySchema": [ { "AttributeName": "City", "KeyType": "HASH" }, { "AttributeName": "Date", "KeyType": "RANGE" } ], "Projection": { "ProjectionType": "INCLUDE", "NonKeyAttributes": [ "State", "Conditions", "Temperatures" ] }, "ProvisionedThroughput": { "ReadCapacityUnits": 5, "WriteCapacityUnits": 5 } } } ]

    In this code:

    • The name of the global secondary index is weather-global-index.

    • The City attribute is the partition key (hash attribute), and the Date attribute is the sort key (range attribute).

    • Projection defines the attributes to retrieve by default (in addition to the hash attribute and any range attribute) for every item matching a table search that uses this index. In this sample, the State, Conditions, HighF (part of Temperatures), and LowF (also part of Temperatures) attributes (as well as the City and Date attributes) are retrieved for every matching item.

    • Similar to tables, a global secondary index must define its provisioned throughput settings.

    • The IndexName, KeySchema, Projection, and ProvisionedThroughput settings must be contained in a Create object, which defines the global secondary index to create when you run the DynamoDB update-table command in the next step.

  2. Run the DynamoDB update-table command.

    aws dynamodb update-table \ --table-name Weather \ --attribute-definitions \ AttributeName=City,AttributeType=S AttributeName=Date,AttributeType=S \ --global-secondary-index-updates file://weather-global-index.json

    In this command:

    • --table-name is the name of the table to update.

    • --attribute-definitions are the attributes to include in the index. The partition key is always listed first, and any sort key is always listed second.

    • --global-secondary-index-updates is the path to the file that defines the global secondary index.

    If this command succeeds, it displays summary information about the new global secondary index that is being created. To confirm the global secondary index is successfully created, run the DynamoDB describe-table command, specifying the table's name (--table-name).

    aws dynamodb describe-table --table-name Weather

    When the global secondary index is successfully created, the TableStatus value changes from UPDATING to ACTIVE, and the IndexStatus value changes from CREATING to ACTIVE. Do not proceed past this step until the global secondary index is successfully created. This can take several minutes.

Step 6: Get Items from the Table

There are many ways to get items from tables. In this step, you get items by using the table's primary key, by using the table's other attributes, and by using the global secondary index.

To get a single item from a table based on the item's primary key value

If you know an item's primary key value, you can get the matching item by running the DynamoDB command get-item , scan , or query . The following are the main differences in these commands:

  • get-item returns a set of attributes for the item with the given primary key.

  • scan returns one or more items and item attributes by accessing every item in a table or a secondary index.

  • query finds items based on primary key values. You can query any table or secondary index that has a composite primary key (a partition key and a sort key).

In this sample, here's how to use each of these commands to get the item that contains the CityID attribute value of 1 and the Date attribute value of 2017-04-12.

  1. To run the DynamoDB get-item command, specify the name of the table (--table-name), the primary key value (--key), and the attribute values for the item to display (--projection-expression). Because Date is a reserved keyword in DynamoDB, you must also provide an alias for the Date attribute value (--expression-attribute-names). (State is also a reserved keyword, and so you will see an alias provided for it in later steps.)

    aws dynamodb get-item \ --table-name Weather \ --key '{ "CityID": { "N": "1" }, "Date": { "S": "2017-04-12" } }' \ --projection-expression \ "City, #D, Conditions, Temperatures.HighF, Temperatures.LowF" \ --expression-attribute-names '{ "#D": "Date" }'

    In this and the other commands, to display all of the item's attributes, don't include --projection-expression. In this example, because you are not including --projection-expression, you also don't need to include --expression-attribute-names.

    aws dynamodb get-item \ --table-name Weather \ --key '{ "CityID": { "N": "1" }, "Date": { "S": "2017-04-12" } }'
  2. To run the DynamoDB scan command, specify:

    • The name of the table (--table-name).

    • The search to run (--filter-expression).

    • The search criteria to use (--expression-attribute-values).

    • The kinds of attributes to display for the matching item (--select).

    • The attribute values for the item to display (--projection-expression).

    • If any of your attributes are using reserved keywords in DynamoDB, aliases for those attributes (--expression-attribute-names).

    aws dynamodb scan \ --table-name Weather \ --filter-expression "(CityID = :cityID) and (#D = :date)" \ --expression-attribute-values \ '{ ":cityID": { "N": "1" }, ":date": { "S": "2017-04-12" } }' \ --select SPECIFIC_ATTRIBUTES \ --projection-expression \ "City, #D, Conditions, Temperatures.HighF, Temperatures.LowF" \ --expression-attribute-names '{ "#D": "Date" }'
  3. To run the DynamoDB query command, specify:

    • The name of the table (--table-name).

    • The search to run (--key-condition-expression).

    • The attribute values to use in the search (--expression-attribute-values).

    • The kinds of attributes to display for the matching item (--select).

    • The attribute values for the item to display (--projection-expression).

    • If any of your attributes are using reserved keywords in DynamoDB, aliases for those attributes (--expression-attribute-names).

    aws dynamodb query \ --table-name Weather \ --key-condition-expression "(CityID = :cityID) and (#D = :date)" \ --expression-attribute-values \ '{ ":cityID": { "N": "1" }, ":date": { "S": "2017-04-12" } }' \ --select SPECIFIC_ATTRIBUTES \ --projection-expression \ "City, #D, Conditions, Temperatures.HighF, Temperatures.LowF" \ --expression-attribute-names '{ "#D": "Date" }'

    Notice that the scan command needed to scan all 9 items to get the result, while the query command only needed to scan for 1 item.

To get multiple items from a table based on the items' primary key values

If you know the items' primary key values, you can get the matching items by running the DynamoDB batch-get-item command. In this sample, here's how to get the items that contain the CityID attribute value of 3 and Date attribute values of 2017-04-13 or 2017-04-14.

Run the DynamoDB batch-get-item command, specifying the path to a file describing the items to get (--request-items).

aws dynamodb batch-get-item --request-items file://batch-get-item.json

For this sample, the code in the batch-get-item.json file specifies to search the Weather table for items with a CityID of 3 and a Date of 2017-04-13 or 2017-04-14. For each item found, the attribute values for City, State, Date, and HighF (part of Temperatures) are displayed, if they exist.

{ "Weather" : { "Keys": [ { "CityID": { "N": "3" }, "Date": { "S": "2017-04-13" } }, { "CityID": { "N": "3" }, "Date": { "S": "2017-04-14" } } ], "ProjectionExpression": "City, #S, #D, Temperatures.HighF", "ExpressionAttributeNames": { "#S": "State", "#D": "Date" } } }

To get all matching items from a table

If you know something about the attributes' values in the table, you can get matching items by running the DynamoDB scan command. In this sample, here's how to get the dates when the Conditions attribute value contains Sunny and the HighF attribute value (part of Temperatures) is greater than 53.

Run the DynamoDB scan command, specifying:

  • The name of the table (--table-name).

  • The search to run (--filter-expression).

  • The search criteria to use (--expression-attribute-values).

  • The kinds of attributes to display for the matching item (--select).

  • The attribute values for the item to display (--projection-expression).

  • If any of your attributes are using reserved keywords in DynamoDB, aliases for those attributes (--expression-attribute-names).

aws dynamodb scan \ --table-name Weather \ --filter-expression \ "(contains (Conditions, :sun)) and (Temperatures.HighF > :h)" \ --expression-attribute-values \ '{ ":sun": { "S" : "Sunny" }, ":h": { "N" : "53" } }' \ --select SPECIFIC_ATTRIBUTES \ --projection-expression "City, #S, #D, Conditions, Temperatures.HighF" \ --expression-attribute-names '{ "#S": "State", "#D": "Date" }'

To get all matching items from a global secondary index

To search using a global secondary index, use the DynamoDB query command. In this sample, here's how to use the weather-global-index secondary index to get the forecast conditions for cities named Portland for the dates of 2017-04-13 and 2017-04-14.

Run the DynamoDB query command, specifying:

  • The name of the table (--table-name).

  • The name of the global secondary index (--index-name).

  • The search to run (--key-condition-expression).

  • The attribute values to use in the search (--expression-attribute-values).

  • The kinds of attributes to display for the matching item (--select).

  • If any of your attributes are using reserved keywords in DynamoDB, aliases for those attributes (--expression-attribute-names).

aws dynamodb query \ --table-name Weather \ --index-name weather-global-index \ --key-condition-expression "(City = :city) and (#D between :date1 and :date2)" \ --expression-attribute-values \ '{ ":city": { "S" : "Portland" }, ":date1": { "S": "2017-04-13" }, ":date2": { "S": "2017-04-14" } }' \ --select SPECIFIC_ATTRIBUTES \ --projection-expression "City, #S, #D, Conditions, Temperatures.HighF" \ --expression-attribute-names '{ "#S": "State", "#D": "Date" }'

Step 7: Clean Up

To prevent ongoing charges to your AWS account after you're done using this sample, you should delete the table. Deleting the table deletes the global secondary index as well. You should also delete your environment.

To delete the table, run the DynamoDB delete-table command, specifying the table's name (--table-name).

aws dynamodb delete-table --table-name Weather

If the command succeeds, information about the table is displayed, including the TableStatus value of DELETING.

To confirm the table is successfully deleted, run the DynamoDB describe-table command, specifying the table's name (--table-name).

aws dynamodb describe-table --table-name Weather

If the table is successfully deleted, a message containing the phrase Requested resource not found is displayed.

To delete your environment, see Deleting an Environment.