Tablestore:Read a range of data

Prerequisites

Initialize the Tablestore client

Methods

public GetRangeResponse GetRange(GetRangeRequest request)

Asynchronous method:

public Task<GetRangeResponse> GetRangeAsync(GetRangeRequest request)

Code examples

Read all rows from test_table where the primary key is greater than row1:

try
{
    // Set the start primary key.
    PrimaryKey inclusiveStartPrimaryKey = new PrimaryKey()
    {
        { "id", new ColumnValue("row1") }
    };
    // Set the end primary key. The result set excludes the end primary key.
    PrimaryKey exclusiveEndPrimaryKey = new PrimaryKey()
    {
        { "id", ColumnValue.INF_MAX }
    };

    // Call the GetRange method to read rows.
    GetRangeRequest getRangeRequest = new GetRangeRequest("test_table", GetRangeDirection.Forward, inclusiveStartPrimaryKey, exclusiveEndPrimaryKey);
    GetRangeResponse getRangeResponse = client.GetRange(getRangeRequest);

    // Process the response.
    Console.WriteLine($"RequestId: {getRangeResponse.RequestID}");
    Console.WriteLine($"Read CU Cost: {getRangeResponse.ConsumedCapacityUnit.Read}");
    Console.WriteLine($"Write CU Cost: {getRangeResponse.ConsumedCapacityUnit.Write}");
    Console.WriteLine("Row Data: ");
    foreach (Row row in getRangeResponse.RowDataList)
    {
        Console.WriteLine(row);
    }
}
catch (Exception ex)
{
    Console.WriteLine($"Get Range failed, exception: {ex.Message}");
}

A single GetRange request returns up to 5,000 rows or 4 MB of data. If more data matches, the response includes a NextPrimaryKey value. Use it as the inclusiveStartPrimaryKey in subsequent requests to paginate. The following example loops through all matching rows:

while (true)
{
    // Call the GetRange method to read rows.
    GetRangeRequest getRangeRequest = new GetRangeRequest("test_table", GetRangeDirection.Forward, inclusiveStartPrimaryKey, exclusiveEndPrimaryKey);
    GetRangeResponse getRangeResponse = client.GetRange(getRangeRequest);

    // Process the response.
    Console.WriteLine($"RequestId: {getRangeResponse.RequestID}");
    Console.WriteLine($"Read CU Cost: {getRangeResponse.ConsumedCapacityUnit.Read}");
    Console.WriteLine($"Write CU Cost: {getRangeResponse.ConsumedCapacityUnit.Write}");
    Console.WriteLine("Row Data: ");
    foreach (Row row in getRangeResponse.RowDataList)
    {
        Console.WriteLine(row);
    }

    if (getRangeResponse.NextPrimaryKey != null)
    {
        inclusiveStartPrimaryKey = getRangeResponse.NextPrimaryKey;
    }
    else
    {
        break;
    }
}

Additional query options:

• Read backward.

  // Set the start primary key. For a backward read, the start primary key must be greater than the end primary key.
  PrimaryKey inclusiveStartPrimaryKey = new PrimaryKey()
  {
      { "id", ColumnValue.INF_MAX }
  };
  // Set the end primary key. The result set excludes the end primary key.
  PrimaryKey exclusiveEndPrimaryKey = new PrimaryKey()
  {
      { "id", new ColumnValue("row1") }
  };
  
  // Call the GetRange method to read rows backward.
  GetRangeRequest getRangeRequest = new GetRangeRequest("test_table", GetRangeDirection.Backward, inclusiveStartPrimaryKey, exclusiveEndPrimaryKey);

• Return specific columns.

  HashSet<string> columnsToGet = new HashSet<string> { "col2" };
  
  // Call the GetRange method to read rows.
  GetRangeRequest getRangeRequest = new GetRangeRequest("test_table", GetRangeDirection.Forward, inclusiveStartPrimaryKey, exclusiveEndPrimaryKey, columnsToGet, null);

• Limit row count.

  int limit = 10;
  
  // Call the GetRange method to read rows.
  GetRangeRequest getRangeRequest = new GetRangeRequest("test_table", GetRangeDirection.Forward, inclusiveStartPrimaryKey, exclusiveEndPrimaryKey, null, limit);

Related topics

• Batch read data

• Iterating through data