Smaws_Client_DynamoDB.Scanval request :
Smaws_Lib.Context.t ->
scan_input ->
(scan_output,
[> Smaws_Lib.Protocols.AwsJson.error
| `InternalServerError of internal_server_error
| `InvalidEndpointException of invalid_endpoint_exception
| `ProvisionedThroughputExceededException of
provisioned_throughput_exceeded_exception
| `RequestLimitExceeded of request_limit_exceeded
| `ResourceNotFoundException of resource_not_found_exception ])
Stdlib.resultThe Scan operation returns one or more items and item attributes by accessing every item in a table or a secondary index. To have DynamoDB return fewer items, you can provide a FilterExpression operation.
If the total size of scanned items exceeds the maximum dataset size limit of 1 MB, the scan completes and results are returned to the user. The LastEvaluatedKey value is also returned and the requestor can use the LastEvaluatedKey to continue the scan in a subsequent operation. Each scan response also includes number of items that were scanned (ScannedCount) as part of the request. If using a FilterExpression, a scan result can result in no items meeting the criteria and the Count will result in zero. If you did not use a FilterExpression in the scan request, then Count is the same as ScannedCount.
Count and ScannedCount only return the count of items specific to a single scan request and, unless the table is less than 1MB, do not represent the total number of items in the table.
A single Scan operation first reads up to the maximum number of items set (if using the Limit parameter) or a maximum of 1 MB of data and then applies any filtering to the results if a FilterExpression is provided. If LastEvaluatedKey is present in the response, pagination is required to complete the full table scan. For more information, see Paginating the Results in the Amazon DynamoDB Developer Guide.
Scan operations proceed sequentially; however, for faster performance on a large table or secondary index, applications can request a parallel Scan operation by providing the Segment and TotalSegments parameters. For more information, see Parallel Scan in the Amazon DynamoDB Developer Guide.
By default, a Scan uses eventually consistent reads when accessing the items in a table. Therefore, the results from an eventually consistent Scan may not include the latest item changes at the time the scan iterates through each item in the table. If you require a strongly consistent read of each item as the scan iterates through the items in the table, you can set the ConsistentRead parameter to true. Strong consistency only relates to the consistency of the read at the item level.
DynamoDB does not provide snapshot isolation for a scan operation when the ConsistentRead parameter is set to true. Thus, a DynamoDB scan operation does not guarantee that all reads in a scan see a consistent snapshot of the table when the scan operation was requested.