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| +.. dynamodb_tut:
|
| +
|
| +============================================
|
| +An Introduction to boto's DynamoDB interface
|
| +============================================
|
| +
|
| +This tutorial focuses on the boto interface to AWS' DynamoDB_. This tutorial
|
| +assumes that you have boto already downloaded and installed.
|
| +
|
| +.. _DynamoDB: http://aws.amazon.com/dynamodb/
|
| +
|
| +Creating a Connection
|
| +---------------------
|
| +
|
| +The first step in accessing DynamoDB is to create a connection to the service.
|
| +To do so, the most straight forward way is the following::
|
| +
|
| + >>> import boto
|
| + >>> conn = boto.connect_dynamodb(
|
| + aws_access_key_id='<YOUR_AWS_KEY_ID>',
|
| + aws_secret_access_key='<YOUR_AWS_SECRET_KEY>')
|
| + >>> conn
|
| + <boto.dynamodb.layer2.Layer2 object at 0x3fb3090>
|
| +
|
| +Bear in mind that if you have your credentials in boto config in your home
|
| +directory, the two keyword arguments in the call above are not needed. More
|
| +details on configuration can be found in :doc:`boto_config_tut`.
|
| +
|
| +.. note:: At this
|
| + time, Amazon DynamoDB is available only in the US-EAST-1 region. The
|
| + ``connect_dynamodb`` method automatically connect to that region.
|
| +
|
| +The :py:func:`boto.connect_dynamodb` functions returns a
|
| +:py:class:`boto.dynamodb.layer2.Layer2` instance, which is a high-level API
|
| +for working with DynamoDB. Layer2 is a set of abstractions that sit atop
|
| +the lower level :py:class:`boto.dynamodb.layer1.Layer1` API, which closely
|
| +mirrors the Amazon DynamoDB API. For the purpose of this tutorial, we'll
|
| +just be covering Layer2.
|
| +
|
| +Listing Tables
|
| +--------------
|
| +
|
| +Now that we have a DynamoDB connection object, we can then query for a list of
|
| +existing tables in that region::
|
| +
|
| + >>> conn.list_tables()
|
| + ['test-table', 'another-table']
|
| +
|
| +Creating Tables
|
| +---------------
|
| +
|
| +DynamoDB tables are created with the
|
| +:py:meth:`Layer2.create_table <boto.dynamodb.layer2.Layer2.create_table>`
|
| +method. While DynamoDB's items (a rough equivalent to a relational DB's row)
|
| +don't have a fixed schema, you do need to create a schema for the table's
|
| +hash key element, and the optional range key element. This is explained in
|
| +greater detail in DynamoDB's `Data Model`_ documentation.
|
| +
|
| +We'll start by defining a schema that has a hash key and a range key that
|
| +are both keys::
|
| +
|
| + >>> message_table_schema = conn.create_schema(
|
| + hash_key_name='forum_name',
|
| + hash_key_proto_value='S',
|
| + range_key_name='subject',
|
| + range_key_proto_value='S'
|
| + )
|
| +
|
| +The next few things to determine are table name and read/write throughput. We'll
|
| +defer explaining throughput to the DynamoDB's `Provisioned Throughput`_ docs.
|
| +
|
| +We're now ready to create the table::
|
| +
|
| + >>> table = conn.create_table(
|
| + name='messages',
|
| + schema=message_table_schema,
|
| + read_units=10,
|
| + write_units=10
|
| + )
|
| + >>> table
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| + Table(messages)
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| +
|
| +This returns a :py:class:`boto.dynamodb.table.Table` instance, which provides
|
| +simple ways to create (put), update, and delete items.
|
| +
|
| +.. _Data Model: http://docs.amazonwebservices.com/amazondynamodb/latest/developerguide/DataModel.html
|
| +.. _Provisioned Throughput: http://docs.amazonwebservices.com/amazondynamodb/latest/developerguide/ProvisionedThroughputIntro.html
|
| +
|
| +Getting a Table
|
| +---------------
|
| +
|
| +To retrieve an existing table, use
|
| +:py:meth:`Layer2.get_table <boto.dynamodb.layer2.Layer2.get_table>`::
|
| +
|
| + >>> conn.list_tables()
|
| + ['test-table', 'another-table', 'messages']
|
| + >>> table = conn.get_table('messages')
|
| + >>> table
|
| + Table(messages)
|
| +
|
| +:py:meth:`Layer2.get_table <boto.dynamodb.layer2.Layer2.get_table>`, like
|
| +:py:meth:`Layer2.create_table <boto.dynamodb.layer2.Layer2.create_table>`,
|
| +returns a :py:class:`boto.dynamodb.table.Table` instance.
|
| +
|
| +Describing Tables
|
| +-----------------
|
| +
|
| +To get a complete description of a table, use
|
| +:py:meth:`Layer2.describe_table <boto.dynamodb.layer2.Layer2.describe_table>`::
|
| +
|
| + >>> conn.list_tables()
|
| + ['test-table', 'another-table', 'messages']
|
| + >>> conn.describe_table('messages')
|
| + {
|
| + 'Table': {
|
| + 'CreationDateTime': 1327117581.624,
|
| + 'ItemCount': 0,
|
| + 'KeySchema': {
|
| + 'HashKeyElement': {
|
| + 'AttributeName': 'forum_name',
|
| + 'AttributeType': 'S'
|
| + },
|
| + 'RangeKeyElement': {
|
| + 'AttributeName': 'subject',
|
| + 'AttributeType': 'S'
|
| + }
|
| + },
|
| + 'ProvisionedThroughput': {
|
| + 'ReadCapacityUnits': 10,
|
| + 'WriteCapacityUnits': 10
|
| + },
|
| + 'TableName': 'messages',
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| + 'TableSizeBytes': 0,
|
| + 'TableStatus': 'ACTIVE'
|
| + }
|
| + }
|
| +
|
| +Adding Items
|
| +------------
|
| +
|
| +Continuing on with our previously created ``messages`` table, adding an::
|
| +
|
| + >>> table = conn.get_table('messages')
|
| + >>> item_data = {
|
| + 'Body': 'http://url_to_lolcat.gif',
|
| + 'SentBy': 'User A',
|
| + 'ReceivedTime': '12/9/2011 11:36:03 PM',
|
| + }
|
| + >>> item = table.new_item(
|
| + # Our hash key is 'forum'
|
| + hash_key='LOLCat Forum',
|
| + # Our range key is 'subject'
|
| + range_key='Check this out!',
|
| + # This has the
|
| + attrs=item_data
|
| + )
|
| +
|
| +The
|
| +:py:meth:`Table.new_item <boto.dynamodb.table.Table.new_item>` method creates
|
| +a new :py:class:`boto.dynamodb.item.Item` instance with your specified
|
| +hash key, range key, and attributes already set.
|
| +:py:class:`Item <boto.dynamodb.item.Item>` is a :py:class:`dict` sub-class,
|
| +meaning you can edit your data as such::
|
| +
|
| + item['a_new_key'] = 'testing'
|
| + del item['a_new_key']
|
| +
|
| +After you are happy with the contents of the item, use
|
| +:py:meth:`Item.put <boto.dynamodb.item.Item.put>` to commit it to DynamoDB::
|
| +
|
| + >>> item.put()
|
| +
|
| +Retrieving Items
|
| +----------------
|
| +
|
| +Now, let's check if it got added correctly. Since DynamoDB works under an
|
| +'eventual consistency' mode, we need to specify that we wish a consistent read,
|
| +as follows::
|
| +
|
| + >>> table = conn.get_table('messages')
|
| + >>> item = table.get_item(
|
| + # Your hash key was 'forum_name'
|
| + hash_key='LOLCat Forum',
|
| + # Your range key was 'subject'
|
| + range_key='Check this out!'
|
| + )
|
| + >>> item
|
| + {
|
| + # Note that this was your hash key attribute (forum_name)
|
| + 'forum_name': 'LOLCat Forum',
|
| + # This is your range key attribute (subject)
|
| + 'subject': 'Check this out!'
|
| + 'Body': 'http://url_to_lolcat.gif',
|
| + 'ReceivedTime': '12/9/2011 11:36:03 PM',
|
| + 'SentBy': 'User A',
|
| + }
|
| +
|
| +Updating Items
|
| +--------------
|
| +
|
| +To update an item's attributes, simply retrieve it, modify the value, then
|
| +:py:meth:`Item.put <boto.dynamodb.item.Item.put>` it again::
|
| +
|
| + >>> table = conn.get_table('messages')
|
| + >>> item = table.get_item(
|
| + hash_key='LOLCat Forum',
|
| + range_key='Check this out!'
|
| + )
|
| + >>> item['SentBy'] = 'User B'
|
| + >>> item.put()
|
| +
|
| +Deleting Items
|
| +--------------
|
| +
|
| +To delete items, use the
|
| +:py:meth:`Item.delete <boto.dynamodb.item.Item.delete>` method::
|
| +
|
| + >>> table = conn.get_table('messages')
|
| + >>> item = table.get_item(
|
| + hash_key='LOLCat Forum',
|
| + range_key='Check this out!'
|
| + )
|
| + >>> item.delete()
|
| +
|
| +Deleting Tables
|
| +---------------
|
| +
|
| +.. WARNING::
|
| + Deleting a table will also **permanently** delete all of its contents without prompt. Use carefully.
|
| +
|
| +There are two easy ways to delete a table. Through your top-level
|
| +:py:class:`Layer2 <boto.dynamodb.layer2.Layer2>` object::
|
| +
|
| + >>> conn.delete_table(table)
|
| +
|
| +Or by getting the table, then using
|
| +:py:meth:`Table.delete <boto.dynamodb.table.Table.delete>`::
|
| +
|
| + >>> table = conn.get_table('messages')
|
| + >>> table.delete()
|
|
|