Use the atomic counter feature

Prerequisites

• An OTSClient instance is initialized. For more information, see Initialize an OTSClient instance.

• A data table is created, and data is written to the data table. For more information, see Create data tables and Write data.

Usage notes

• You can implement atomic counters only on INTEGER columns.

• If a column that is specified as an atomic counter does not exist before you write data, the default value of the column is 0. If a column that is specified as an atomic counter is not an INTEGER column, an OTSParameterInvalid error occurs.

• You can update an atomic counter by using a positive or negative number, but you must avoid an integer overflow. If an integer overflow occurs, an OTSParameterInvalid error is returned.

• By default, the value of an atomic counter is not returned in the response to an update row request. You can specify that the updated value of an atomic counter is returned.

• You cannot specify a column as an atomic counter and update the column in a single update request. For example, if you set Column A to an atomic counter, you cannot perform other operations such as overwrite and delete operations on the column at the same time.

• You can perform multiple update operations on the same row by sending a BatchWriteRow request. However, if you perform an atomic counter operation on a row, you can perform only one update operation on the row in a BatchWriteRow request.

• Only the value of the latest version of an atomic counter can be updated. You cannot update the value of a specified version of an atomic counter. After an update operation is complete, a new version of data is inserted into the atomic counter in the row.

API operations

Parameters

Example

public static void Increment(int incrementValue)
{
    Console.WriteLine("Start set increment column...");
    OTSClient otsClient = Config.GetClient();

    // Specify the primary key of the row. The primary key must be consistent with the primary key specified in TableMeta when you create the table. 
    PrimaryKey primaryKey = new PrimaryKey
    {
        { Pk1, new ColumnValue(0) },
        { Pk2, new ColumnValue("abc") }
    };
    RowUpdateChange rowUpdateChange = new RowUpdateChange(TableName, primaryKey); // Specify the name of the data table. 
    // Set the ReturnType parameter to ReturnType.RT_AFTER_MODIFY to return the values of the column on which atomic counter operations are performed. 
    rowUpdateChange.ReturnType = ReturnType.RT_AFTER_MODIFY;
    rowUpdateChange.ReturnColumnNames = new List<string>() { IncrementCol};
    // Specify the column on which atomic counter operations are performed. The column value starts from 0 and increases by the number specified by the incrementValue parameter. 
    rowUpdateChange.Increment(new Column(IncrementCol, new ColumnValue(incrementValue)));

    UpdateRowRequest updateRowRequest = new UpdateRowRequest(rowUpdateChange);

    var response = otsClient.UpdateRow(updateRowRequest);
    Console.WriteLine("set Increment column succeed Increment result:" + response.Row.GetColumns()[0].Value);
}