Tablestore:Read data whose primary key values are in the specified range

Prerequisites

A client is initialized. For more information, see Initialize a Tablestore client.

Method description

public GetRangeResponse getRange(GetRangeRequest getRangeRequest) throws TableStoreException, ClientException

Sample code

The following sample code reads data from the test_table table where the primary key value is greater than row1.

public static void getRangeExample(SyncClient client) {
    // Construct the query conditions.
    RangeRowQueryCriteria rangeRowQueryCriteria = new RangeRowQueryCriteria("test_table");
    // Specify the start primary key for the query.
    PrimaryKeyBuilder primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
    primaryKeyBuilder.addPrimaryKeyColumn("id", PrimaryKeyValue.fromString("row1"));
    rangeRowQueryCriteria.setInclusiveStartPrimaryKey(primaryKeyBuilder.build());
    // Specify the end primary key. The result does not include the end primary key.
    primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
    primaryKeyBuilder.addPrimaryKeyColumn("id", PrimaryKeyValue.INF_MAX);
    rangeRowQueryCriteria.setExclusiveEndPrimaryKey(primaryKeyBuilder.build());
    // Specify the version that you want to query.
    rangeRowQueryCriteria.setMaxVersions(1);

    // Call the getRange method to query data.
    GetRangeRequest getRangeRequest = new GetRangeRequest(rangeRowQueryCriteria);
    GetRangeResponse getRangeResponse = client.getRange(getRangeRequest);

    // Return the result.
    System.out.println("RequestId: " + getRangeResponse.getRequestId());
    System.out.println("Read CU Cost: " + getRangeResponse.getConsumedCapacity().getCapacityUnit().getReadCapacityUnit());
    System.out.println("Write CU Cost: " + getRangeResponse.getConsumedCapacity().getCapacityUnit().getWriteCapacityUnit());
    for(Row row : getRangeResponse.getRows())
        System.out.println(row);
}

The maximum amount of data that can be scanned in a single range read operation is 5,000 rows or 4 MB. If the limit is exceeded, the primary key value for the next read operation is returned. You can refer to the following code for iterative queries.

while(true) {
    GetRangeRequest getRangeRequest = new GetRangeRequest(rangeRowQueryCriteria);
    GetRangeResponse getRangeResponse = client.getRange(getRangeRequest);

    // Return the result.
    System.out.println("RequestId: " + getRangeResponse.getRequestId());
    System.out.println("Read CU Cost: " + getRangeResponse.getConsumedCapacity().getCapacityUnit().getReadCapacityUnit());
    System.out.println("Write CU Cost: " + getRangeResponse.getConsumedCapacity().getCapacityUnit().getWriteCapacityUnit());
    for(Row row : getRangeResponse.getRows())
        System.out.println(row);
    System.out.println("Rows Count: " + getRangeResponse.getRows().size());

    // Specify the start primary key for the next read operation.
    if(getRangeResponse.getNextStartPrimaryKey() != null)
        rangeRowQueryCriteria.setInclusiveStartPrimaryKey(getRangeResponse.getNextStartPrimaryKey());
    else break;
}

You can also refer to the following sample code to configure the following settings when you query data.

• Specify the direction in which data is read.

  // Specify that data is read in the backward direction.
  rangeRowQueryCriteria.setDirection(Direction.BACKWARD);
  // Specify the start primary key. When you read data in the backward direction, the start primary key must be greater than the end primary key.
  PrimaryKeyBuilder primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
  primaryKeyBuilder.addPrimaryKeyColumn("id", PrimaryKeyValue.INF_MAX);
  rangeRowQueryCriteria.setInclusiveStartPrimaryKey(primaryKeyBuilder.build());
  // Specify the end primary key. The result does not include the end primary key.
  primaryKeyBuilder = PrimaryKeyBuilder.createPrimaryKeyBuilder();
  primaryKeyBuilder.addPrimaryKeyColumn("id", PrimaryKeyValue.fromString("row1"));
  rangeRowQueryCriteria.setExclusiveEndPrimaryKey(primaryKeyBuilder.build());

• Specify the version range of data to read. Only data within the version range is returned.

  // Specify the version range of data to query to one day before the current time.
  rangeRowQueryCriteria.setTimeRange(new TimeRange(System.currentTimeMillis() - 86400*1000, System.currentTimeMillis()));

• Specify the attribute columns to read.

  rangeRowQueryCriteria.addColumnsToGet("col2");

• Specify the maximum number of rows to return in a single operation.

  rangeRowQueryCriteria.setLimit(10);

References

• Use the local transaction feature

• Read multiple rows of data at the same time

• Read data by using an iterator

• Use TableStoreReader to concurrently read data