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 16 MB of data, which can contain as many as 100
BatchGetItem returns 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.
If you request more than 100 items,
BatchGetItem returns a
ValidationException with the message "Too many items requested for
the BatchGetItem call."
For example, if you ask to retrieve 100 items, but each individual item is 300 KB in
size, the system returns 52 items (so as not to exceed the 16 MB limit). It also returns
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 returns 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
If DynamoDB returns any unprocessed items, you should retry the batch operation on those items. However, we strongly recommend that you use an exponential backoff algorithm. If you retry the batch operation immediately, the underlying read or write requests can still fail due to throttling on the individual tables. If you delay the batch operation using exponential backoff, the individual requests in the batch are much more likely to succeed.
For more information, see Batch Operations and Error Handling in the Amazon DynamoDB Developer Guide.
BatchGetItem performs eventually consistent reads on every
table in the request. If you want strongly consistent reads instead, you can set
true for any or all tables.
In order to minimize response latency,
BatchGetItem retrieves items in
When designing your application, keep in mind that DynamoDB does not return items in
any particular order. To help parse the response by item, include the primary key values
for the items in your request in the
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 Working with Tables in the Amazon DynamoDB Developer Guide.