AWS SDK for .NET Documentation
Scan Method (scanRequest)
Amazon ► Amazon.DynamoDBv2 ► AmazonDynamoDBClient ► Scan(ScanRequest)
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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.

Declaration Syntax

C#

    public ScanResponse Scan(
    	ScanRequest scanRequest
    )

Parameters

scanRequest (ScanRequest)
  Container for the necessary parameters to execute the Scan service method on AmazonDynamoDBv2.

Return Value
The response from the Scan service method, as returned by AmazonDynamoDBv2.
Examples

The following example shows how to scan items in a table.
Note: the Scan operation goes through every item in the table to check if the item matches all the scan conditions. This makes the Scan operation particularly slow and expensive (in terms of provisioned throughput).
We will now retrieve all items where the Pages attribute is greater than the numerical value "200" and where the Title attribute contains the string "Adventures".

CopyScan sample

    // Create a client
    AmazonDynamoDBClient client = new AmazonDynamoDBClient();

    // Define scan conditions
    Dictionary<string, Condition> conditions = new Dictionary<string, Condition>();

    // Title attribute should contain the string "Adventures"
    Condition titleCondition = new Condition();
    titleCondition.WithComparisonOperator("CONTAINS");
    titleCondition.WithAttributeValueList(new AttributeValue { S = "Adventures" });
    conditions["Title"] = titleCondition;

    // Pages attributes must be greater-than the numeric value "200"
    Condition pagesCondition = new Condition();
    pagesCondition.WithComparisonOperator("GT");
    pagesCondition.WithAttributeValueList(new AttributeValue { N = "200" });
    conditions["Pages"] = pagesCondition;

    // Define marker variable
    Dictionary<string, AttributeValue> startKey = null;

    do
    {
        // Create Scan request
        ScanRequest request = new ScanRequest
        {
            TableName = "SampleTable",
            ExclusiveStartKey = startKey,
            ScanFilter = conditions
        };

        // Issue request
        ScanResult result = client.Scan(request).ScanResult;

        // View all returned items
        List<Dictionary<string, AttributeValue>> items = result.Items;
        foreach (Dictionary<string, AttributeValue> item in items)
        {
            Console.WriteLine("Item:");
            foreach (var keyValuePair in item)
            {
                Console.WriteLine("{0} : S={1}, N={2}, SS=[{3}], NS=[{4}]",
                    keyValuePair.Key,
                    keyValuePair.Value.S,
                    keyValuePair.Value.N,
                    string.Join(", ", keyValuePair.Value.SS ?? new List<string>()),
                    string.Join(", ", keyValuePair.Value.NS ?? new List<string>()));
            }
        }

        // Set marker variable
        startKey = result.LastEvaluatedKey;
    } while (startKey != null);

The following example shows how we can utilize parallel scan to partition a table into 10 segments and scan each segment in a separate thread.
To avoid resource contention between threads, the results will be written into 10 separate files. Each segment will have a file of its own.

CopyParallel scan sample

    // Create a client
    AmazonDynamoDBClient client = new AmazonDynamoDBClient();

    // Define scan conditions
    Dictionary<string, Condition> conditions = new Dictionary<string, Condition>();

    // Pages attributes must be greater-than the numeric value "200"
    Condition pagesCondition = new Condition();
    pagesCondition.WithComparisonOperator("GT");
    pagesCondition.WithAttributeValueList(new AttributeValue { N = "200" });
    conditions["Pages"] = pagesCondition;

    // Setup 10 simultaneous threads, each thread calling Scan operation
    // with its own segment value.
    int totalSegments = 10;
    Parallel.For(0, totalSegments, segment =>
    {
        // Define marker variable
        Dictionary<string, AttributeValue> startKey = null;

        do
        {
            // Create Scan request
            ScanRequest request = new ScanRequest
            {
                TableName = "SampleTable",
                ExclusiveStartKey = startKey,
                ScanFilter = conditions,
                // Total segments to split the table into
                TotalSegments = totalSegments,
                // Current segment to scan
                Segment = segment
            };

            // Issue request
            ScanResult result = client.Scan(request).ScanResult;

            // Write returned items to file
            string path = string.Format("ParallelScan-{0}-of-{1}.txt", totalSegments, segment);
            List<Dictionary<string, AttributeValue>> items = result.Items;
            using (Stream stream = File.OpenWrite(path))
            using (StreamWriter writer = new StreamWriter(stream))
            {
                foreach (Dictionary<string, AttributeValue> item in items)
                {
                    writer.WriteLine("Item:");
                    foreach (var keyValuePair in item)
                    {
                        writer.WriteLine("{0} : S={1}, N={2}, SS=[{3}], NS=[{4}]",
                            keyValuePair.Key,
                            keyValuePair.Value.S,
                            keyValuePair.Value.N,
                            string.Join(", ", keyValuePair.Value.SS ?? new List<string>()),
                            string.Join(", ", keyValuePair.Value.NS ?? new List<string>()));
                    }
                }
            }

            // Set marker variable
            startKey = result.LastEvaluatedKey;
        } while (startKey != null);
    });

Exceptions

Exception | Condition
--- | ---
ResourceNotFoundException |
ProvisionedThroughputExceededException |
InternalServerErrorException |

Assembly: AWSSDK (Module: AWSSDK) Version: 1.5.60.0 (1.5.60.0)