Delete Group Data in Cache with SQL

Note

This feature is only available in NCache Enterprise Edition.

Similar to searching with SQL, NCache provides object queries through which you use a criteria given in a query delete result sets. To delete the data in the cache according to your specified criteria, NCache provides you with an extension of SQL.

A special keyword $Group$ is used to specify that the condition under consideration uses group. A query with the searching criteria is executed using ExecuteNonQuery.

ExecuteNonQuery processes the query on the server-side and then sends the result to the client in the tabular form to the ICacheReader type of instance.

Prerequisites

To learn about the standard prerequisites required to work with all NCache client side features please refer to the given page on Client Side API Prerequisites.
Custom classes/searchable attributes must be indexed as explained in Configuring Query Indexes.
For API details refer to: ICache, ICacheReader, QueryCommand, ExecuteNonQuery, SearchService.

Delete Group

Given a certain criteria, you can remove groups present in the cache with SQL queries. The following example removes all the data against a certain group through the SQL delete query.

try
{
    // Pre-conditions: Cache is already connected

    /*A user wants to remove the West Coast Customers Group 
    as this region is no longer supported in their store.Custom class is query indexed through NCache Web Manager or config.ncconf*/

    // Create SQL Query with the specified criteria
    // Make sure to use the Fully Qualified Name (FQN)
    string query = "DELETE FROM Alachisoft.NCache.Samples.Data.Customer WHERE $Group$ = ?"; 

    // Use QueryCommand for query execution
    var queryCommand = new QueryCommand(query);

    // Providing parameters for query
    queryCommand.Parameters.Add("$Group$", "West Coast  Customers"); 

    // 'rowsAffected' number of items removed from cache
    int rowsAffected = cache.SearchService.ExecuteNonQuery(queryCommand);

    if (rowsAffected==0)
        Console.WriteLine($"No west coast customers removed");
}
catch (OperationFailedException ex)
{
    if (ex.ErrorCode == NCacheErrorCodes.INCORRECT_FORMAT)
    {
        // Make sure that the query format is correct
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures 
        // Operation Timeout
        // Operation performed during state transfer    
    }
}
catch (Exception ex)
{
    // Any other generic exception like ArgumentNullException or ArgumentException
}

try
{
    // Pre-conditions: Cache is already connected
    // Custom class is query indexed through NCache Web Manager or config.ncconf

    // Create SQL Query with the specified criteria
    // Make sure to use the Fully Qualified Name (FQN)
    String query = "DELETE FROM FQN.Customer WHERE $Group$ = ?";

    // Use QueryCommand for query execution
    QueryCommand queryCommand = new QueryCommand(query);

    queryCommand.getParameters().put("$Group$","ImportantCustomers");

    // rowsAffected is the number of items removed from cache
    int rowsAffected = cache.getSearchService().executeNonQuery(queryCommand);
}
catch (OperationFailedException ex)
{
    if (ex.getErrorCode() == NCacheErrorCodes.INCORRECT_FORMAT)
    {
        // Make sure that the query format is correct
    }
    else
    {
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like NullPointerException or IllegalArgumentException
}

try {
    // Pre-conditions: Cache is already connected
    // Custom class is query indexed through NCache Web Manager or config.ncconf

    // Create SQL Query with the specified criteria
    // Make sure to use the Fully Qualified Name (FQN)
    val query = "DELETE FROM FQN.Customer WHERE $Group$ = ?"

    // Use QueryCommand for query execution
    val queryCommand = new QueryCommand(query)

    queryCommand.setParameters(Map("$Group$" -> "ImportantCustomers"))

    // rowsAffected is the number of items removed from cache
    val rowsAffected = cache.getSearchService.executeNonQuery(queryCommand)
}
catch {
    case exception: Exception => {
      // Handle any errors
    }
}

// This is an async method
try
{
    // Pre-conditions: Cache is already connected
    // Custom class is query indexed through NCache Web Manager or config.ncconf

    // Create SQL Query with the specified criteria
    // Make sure to use the Fully Qualified Name (FQN)
    var query = "DELETE FROM FQN.Customer WHERE $Group$ = ?";

    // Use QueryCommand for query execution
    var queryCommand = new ncache.QueryCommand(query);

    var parameters = this.map.set("$Group","Important Customers");
    queryCommand.setParameters(parameters);

    var searchService = await this.cache.getSearchService();

    // rowsAffected is the number of items removed from cache
    var rowsAffected = await searchService.executeReader(queryCommand);
}
catch(error)
{
   // Handle errors
}

try:
    # Pre-conditions: Cache is already connected
    # Custom class is query indexed through NCache Web Manager or config.ncconf

    # Create SQL Query with the specified criteria
    # Make sure to use the Fully Qualified Name(FQN)
    query = "DELETE FROM FQN.Customer WHERE $Group$ = ?"

    # Use QueryCommand for query execution
    query_command = ncache.QueryCommand(query)

    parameters = {"$Group": "Important Customers"}
    query_command.set_parameters(parameters)

    search_service = cache.get_search_service()

    # rows_affected is the number of items removed from cache
    rows_affected = search_service.execute_non_query(query_command)

except Exception as exp:
    # Handle errors

Note

To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

In order to get more detail on object queries please refer to the SQL Reference for NCache section.

Additional Resources

NCache provides sample application for Groups on GitHub.

Delete Group Data in Cache with SQL

Note

Prerequisites

Delete Group

Note

Additional Resources

See Also