Implement atomic counter by using Tablestore SDK for Node.js - Tablestore

If you want to use a counter for your online application, you can use the atomic counter feature. To use this feature, specify a column as an atomic counter and perform atomic counter operations on the column.

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.

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

The atomic counter-related operation is added to the updateRow operation. The following table describes the atomic counter-related operation.

Operation	Description
updateOfAttributeColumns	Specifies INCREMENT as the update type to increase or decrease a column value by a specific integer.
returnContent	Specifies the name of the column whose value you want to return among the columns on which operations are performed to implement atomic counter.

Parameter

Parameter	Description
tableName	The name of the data table.
columnName	The name of the column on which you want to perform atomic counter operations. You can implement atomic counters only on INTEGER columns.
value	The increment or decrement in the column value.
returnColumns	Specifies the name of the column whose value you want to return among the columns on which operations are performed to implement atomic counter.
returnType	Sets the return type to TableStore.ReturnType.AfterModify to return the values of the columns on which operations are performed to implement atomic counter.

Example

The following sample code provides an example on how to use INCREMENT as the update type to update the value of an attribute column of the INTEGER type when you call the updateRow operation to update data:

var params = {
  tableName: "<Your-Table-Name>",
  condition: new TableStore.Condition(TableStore.RowExistenceExpectation.EXPECT_EXIST, null),
  primaryKey: [{'pk0': Long.fromNumber(1)}],
  // Specify the price column as an atomic counter and increase the value of the atomic counter by 10. You cannot specify the timestamp. 
  updateOfAttributeColumns: [
    {'INCREMENT': [{'price': Long.fromNumber(10)}]}
  ],
  // Set the return type to TableStore.ReturnType.AfterModify and return the values of the columns on which operations are performed to implement atomic counter. 
  returnContent: {
    returnColumns: ["price"],
    returnType: TableStore.ReturnType.AfterModify
  }
};

client.updateRow(params,
  function (err, data) {
    if (err) {
      console.log('error:', err);
      return;
    }

    console.log('success:', JSON.stringify(data, null, 2));
  });