The 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 number of scanned items exceeds the maximum data set size limit of 1 MB, the scan stops and results
are returned to the user as a LastEvaluatedKey
value 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.
A single Scan
operation will read up to the maximum number of items set (if using the
Limit
parameter) or a maximum of 1 MB of data and then apply any filtering to the results using
FilterExpression
. If LastEvaluatedKey
is present in the response, you will need to
paginate the result set. 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.
Scan
uses eventually consistent reads when accessing the data in a table; therefore, the result set
might not include the changes to data in the table immediately before the operation began. If you need a
consistent copy of the data, as of the time that the Scan
begins, you can set the
ConsistentRead
parameter to true
.