This is the Amazon DynamoDB API Reference. This guide provides descriptions and samples of the low-level DynamoDB API. For information about DynamoDB application development, go to the Amazon DynamoDB Developer Guide .
Instead of making the requests to the low-level DynamoDB API directly from your application, we recommend that you use the AWS Software Development Kits (SDKs). The easy-to-use libraries in the AWS SDKs make it unnecessary to call the low-level DynamoDB API directly from your application. The libraries take care of request authentication, serialization, and connection management. For more information, go to Using the AWS SDKs with DynamoDB in the Amazon DynamoDB Developer Guide .
If you decide to code against the low-level DynamoDB API directly, you will need to write the necessary code to authenticate your requests. For more information on signing your requests, go to Using the DynamoDB API in the Amazon DynamoDB Developer Guide .
The following are short descriptions of each low-level API action, organized by function.
CreateTable - Creates a table with user-specified provisioned throughput settings. You must designate one attribute as the hash primary key for the table; you can optionally designate a second attribute as the range primary key. DynamoDB creates indexes on these key attributes for fast data access. Optionally, you can create one or more secondary indexes, which provide fast data access using non-key attributes.
DescribeTable - Returns metadata for a table, such as table size, status, and index information.
UpdateTable - Modifies the provisioned throughput settings for a table. Optionally, you can modify the provisioned throughput settings for global secondary indexes on the table.
ListTables - Returns a list of all tables associated with the current AWS account and endpoint.
DeleteTable - Deletes a table and all of its indexes.
For conceptual information about managing tables, go to Working with Tables in the Amazon DynamoDB Developer Guide .
GetItem - Returns a set of attributes for the item that has a given primary key. By default, GetItem performs an eventually consistent read; however, applications can specify a strongly consistent read instead.
BatchGetItem - Performs multiple GetItem requests for data items using their primary keys, from one table or multiple tables. The response from BatchGetItem has a size limit of 1 MB and returns a maximum of 100 items. Both eventually consistent and strongly consistent reads can be used.
Query - Returns one or more items from a table or a secondary index. You must provide a specific hash key value. You can narrow the scope of the query using comparison operators against a range key value, or on the index key. Query supports either eventual or strong consistency. A single response has a size limit of 1 MB.
Scan - Reads every item in a table; the result set is eventually consistent. You can limit the number of items returned by filtering the data attributes, using conditional expressions. Scan can be used to enable ad-hoc querying of a table against non-key attributes; however, since this is a full table scan without using an index, Scan should not be used for any application query use case that requires predictable performance.
PutItem - Creates a new item, or replaces an existing item with a new item (including all the attributes). By default, if an item in the table already exists with the same primary key, the new item completely replaces the existing item. You can use conditional operators to replace an item only if its attribute values match certain conditions, or to insert a new item only if that item doesn't already exist.
UpdateItem - Modifies the attributes of an existing item. You can also use conditional operators to perform an update only if the item's attribute values match certain conditions.
DeleteItem - Deletes an item in a table by primary key. You can use conditional operators to perform a delete an item only if the item's attribute values match certain conditions.
BatchWriteItem - Performs multiple PutItem and DeleteItem requests across multiple tables in a single request. A failure of any request(s) in the batch will not cause the entire BatchWriteItem operation to fail. Supports batches of up to 25 items to put or delete, with a maximum total request size of 1 MB.
public interface AmazonDynamoDB : IDisposable
The BatchGetItem operation returns the attributes of one or more items from one or more tables. You identify requested items by primary key.
A single operation can retrieve up to 1 MB of data, which can contain as many as 100 items. BatchGetItem will return a partial result if the response size limit is exceeded, the table's provisioned throughput is exceeded, or an internal processing failure occurs. If a partial result is returned, the operation returns a value for UnprocessedKeys . You can use this value to retry the operation starting with the next item to get.
For example, if you ask to retrieve 100 items, but each individual item is 50 KB in size, the system returns 20 items (1 MB) and an appropriate UnprocessedKeys value so you can get the next page of results. If desired, your application can include its own logic to assemble the pages of results into one dataset.
If none of the items can be processed due to insufficient provisioned throughput on all of the tables in the request, then BatchGetItem will throw a ProvisionedThroughputExceededException . If at least one of the items is successfully processed, then BatchGetItem completes successfully, while returning the keys of the unread items in UnprocessedKeys .
By default, BatchGetItem performs eventually consistent reads on every table in the request. If you want strongly consistent reads instead, you can set ConsistentRead to true for any or all tables.
In order to minimize response latency, BatchGetItem retrieves items in parallel.
When designing your application, keep in mind that DynamoDB does not return attributes in any particular order. To help parse the response by item, include the primary key values for the items in your request in the AttributesToGet parameter.
If a requested item does not exist, it is not returned in the result. Requests for nonexistent items consume the minimum read capacity units according to the type of read. For more information, see Capacity Units Calculations in the Amazon DynamoDB Developer Guide.
The BatchWriteItem operation puts or deletes multiple items in one or more tables. A single call to BatchWriteItem can write up to 1 MB of data, which can comprise as many as 25 put or delete requests. Individual items to be written can be as large as 64 KB.
NOTE: BatchWriteItem cannot update items. To update items, use the UpdateItem API.
The individual PutItem and DeleteItem operations specified in BatchWriteItem are atomic; however BatchWriteItem as a whole is not. If any requested operations fail because the table's provisioned throughput is exceeded or an internal processing failure occurs, the failed operations are returned in the UnprocessedItems response parameter. You can investigate and optionally resend the requests. Typically, you would call BatchWriteItem in a loop. Each iteration would check for unprocessed items and submit a new BatchWriteItem request with those unprocessed items until all items have been processed.
Note that if none of the items can be processed due to insufficient provisioned throughput on all of the tables in the request, then BatchGetItem will throw a ProvisionedThroughputExceededException .
To write one item, you can use the PutItem operation; to delete one item, you can use the DeleteItem operation.
With BatchWriteItem , you can efficiently write or delete large amounts of data, such as from Amazon Elastic MapReduce (EMR), or copy data from another database into DynamoDB. In order to improve performance with these large-scale operations, BatchWriteItem does not behave in the same way as individual PutItem and DeleteItem calls would For example, you cannot specify conditions on individual put and delete requests, and BatchWriteItem does not return deleted items in the response.
If you use a programming language that supports concurrency, such as Java, you can use threads to write items in parallel. Your application must include the necessary logic to manage the threads. With languages that don't support threading, such as PHP, you must update or delete the specified items one at a time. In both situations, BatchWriteItem provides an alternative where the API performs the specified put and delete operations in parallel, giving you the power of the thread pool approach without having to introduce complexity into your application.
Parallel processing reduces latency, but each specified put and delete request consumes the same number of write capacity units whether it is processed in parallel or not. Delete operations on nonexistent items consume one write capacity unit.
If one or more of the following is true, DynamoDB rejects the entire batch write operation:
|BeginBatchGetItem(BatchGetItemRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the BatchGetItem operation.
|BeginBatchWriteItem(BatchWriteItemRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the BatchWriteItem operation.
|BeginCreateTable(CreateTableRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the CreateTable operation.
|BeginDeleteItem(DeleteItemRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the DeleteItem operation.
|BeginDeleteTable(DeleteTableRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the DeleteTable operation.
|BeginDescribeTable(DescribeTableRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the DescribeTable operation.
|BeginGetItem(GetItemRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the GetItem operation.
|BeginListTables(ListTablesRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the ListTables operation.
|BeginPutItem(PutItemRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the PutItem operation.
|BeginQuery(QueryRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the Query operation.
|BeginScan(ScanRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the Scan operation.
|BeginUpdateItem(UpdateItemRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the UpdateItem operation.
|BeginUpdateTable(UpdateTableRequest, AsyncCallback, Object)|
Initiates the asynchronous execution of the UpdateTable operation.
The CreateTable operation adds a new table to your account. In an AWS account, table names must be unique within each region. That is, you can have two tables with same name if you create the tables in different regions.
CreateTable is an asynchronous operation. Upon receiving a CreateTable request, DynamoDB immediately returns a response with a TableStatus of CREATING . After the table is created, DynamoDB sets the TableStatus to ACTIVE . You can perform read and write operations only on an ACTIVE table.
If you want to create multiple tables with secondary indexes on them, you must create them sequentially. Only one table with secondary indexes can be in the CREATING state at any given time.
You can use the DescribeTable API to check the table status.
Deletes a single item in a table by primary key. You can perform a conditional delete operation that deletes the item if it exists, or if it has an expected attribute value.
In addition to deleting an item, you can also return the item's attribute values in the same operation, using the ReturnValues parameter.
Unless you specify conditions, the DeleteItem is an idempotent operation; running it multiple times on the same item or attribute does not result in an error response.
Conditional deletes are useful for only deleting items if specific conditions are met. If those conditions are met, DynamoDB performs the delete. Otherwise, the item is not deleted.
The DeleteTable operation deletes a table and all of its items. After a DeleteTable request, the specified table is in the DELETING state until DynamoDB completes the deletion. If the table is in the ACTIVE state, you can delete it. If a table is in CREATING or UPDATING states, then DynamoDB returns a ResourceInUseException . If the specified table does not exist, DynamoDB returns a ResourceNotFoundException . If table is already in the DELETING state, no error is returned.
NOTE: DynamoDB might continue to accept data read and write operations, such as GetItem and PutItem, on a table in the DELETING state until the table deletion is complete.
When you delete a table, any indexes on that table are also deleted.
Use the DescribeTable API to check the status of the table.
Returns information about the table, including the current status of the table, when it was created, the primary key schema, and any indexes on the table.
Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.(Inherited from IDisposable.)
Finishes the asynchronous execution of the BatchGetItem operation.
Finishes the asynchronous execution of the BatchWriteItem operation.
Finishes the asynchronous execution of the CreateTable operation.
Finishes the asynchronous execution of the DeleteItem operation.
Finishes the asynchronous execution of the DeleteTable operation.
Finishes the asynchronous execution of the DescribeTable operation.
Finishes the asynchronous execution of the GetItem operation.
Finishes the asynchronous execution of the ListTables operation.
Finishes the asynchronous execution of the PutItem operation.
Finishes the asynchronous execution of the Query operation.
Finishes the asynchronous execution of the Scan operation.
Finishes the asynchronous execution of the UpdateItem operation.
Finishes the asynchronous execution of the UpdateTable operation.
The GetItem operation returns a set of attributes for the item with the given primary key. If there is no matching item, GetItem does not return any data.
GetItem provides an eventually consistent read by default. If your application requires a strongly consistent read, set ConsistentRead to true . Although a strongly consistent read might take more time than an eventually consistent read, it always returns the last updated value.
Returns an array of table names associated with the current account and endpoint. The output from ListTables is paginated, with each page returning a maximum of 100 table names.
Returns an array of table names associated with the current account and endpoint. The output from ListTables is paginated, with each page returning a maximum of 100 table names.
Creates a new item, or replaces an old item with a new item. If an item already exists in the specified table with the same primary key, the new item completely replaces the existing item. You can perform a conditional put (insert a new item if one with the specified primary key doesn't exist), or replace an existing item if it has certain attribute values.
In addition to putting an item, you can also return the item's attribute values in the same operation, using the ReturnValues parameter.
When you add an item, the primary key attribute(s) are the only required attributes. Attribute values cannot be null. String and binary type attributes must have lengths greater than zero. Set type attributes cannot be empty. Requests with empty values will be rejected with a ValidationException .
You can request that PutItem return either a copy of the old item (before the update) or a copy of the new item (after the update). For more information, see the ReturnValues description.
NOTE: To prevent a new item from replacing an existing item, use a conditional put operation with Exists set to false for the primary key attribute, or attributes.
For more information about using this API, see Working with Items in the Amazon DynamoDB Developer Guide.
A Query operation directly accesses items from a table using the table primary key, or from an index using the index key. You must provide a specific hash key value. You can narrow the scope of the query by using comparison operators on the range key value, or on the index key. You can use the ScanIndexForward parameter to get results in forward or reverse order, by range key or by index key.
Queries that do not return results consume the minimum read capacity units according to the type of read.
If the total number of items meeting the query criteria exceeds the result set size limit of 1 MB, the query stops and results are returned to the user with a LastEvaluatedKey to continue the query in a subsequent operation. Unlike a Scan operation, a Query operation never returns an empty result set and a LastEvaluatedKey . The LastEvaluatedKey is only provided if the results exceed 1 MB, or if you have used Limit .
You can query a table, a local secondary index, or a global secondary index. For a query on a table or on a local secondary index, you can set ConsistentRead to true and obtain a strongly consistent result. Global secondary indexes support eventually consistent reads only, so do not specify ConsistentRead when querying a global secondary index.
The Scan operation returns one or more items and item attributes by accessing every item in the table. To have DynamoDB return fewer items, you can provide a ScanFilter .
If the total number of scanned items exceeds the maximum data set size limit of 1 MB, the scan stops and results are returned to the user with a LastEvaluatedKey to continue the scan in a subsequent operation. The results also include the number of items exceeding the limit. A scan can result in no table data meeting the filter criteria.
The result set is eventually consistent.
By default, Scan operations proceed sequentially; however, for faster performance on large tables, applications can request a parallel Scan by specifying the Segment and TotalSegments parameters. For more information, see Parallel Scan in the Amazon DynamoDB Developer Guide.
Edits an existing item's attributes, or inserts a new item if it does not already exist. You can put, delete, or add attribute values. You can also perform a conditional update (insert a new attribute name-value pair if it doesn't exist, or replace an existing name-value pair if it has certain expected attribute values).
In addition to updating an item, you can also return the item's attribute values in the same operation, using the ReturnValues parameter.
Updates the provisioned throughput for the given table. Setting the throughput for a table helps you manage performance and is part of the provisioned throughput feature of DynamoDB.
The provisioned throughput values can be upgraded or downgraded based on the maximums and minimums listed in the Limits section in the Amazon DynamoDB Developer Guide.
The table must be in the ACTIVE state for this operation to succeed. UpdateTable is an asynchronous operation; while executing the operation, the table is in the UPDATING state. While the table is in the UPDATING state, the table still has the provisioned throughput from before the call. The new provisioned throughput setting is in effect only when the table returns to the ACTIVE state after the UpdateTable operation.
You cannot add, modify or delete indexes using UpdateTable . Indexes can only be defined at table creation time.