Delete Group Data in Cache with SQL Query

Similar to searching with SQL, NCache provides object queries through which you use criteria given in a query to delete result sets. To delete the data in the cache according to your specified criteria, NCache provides you with an extension of SQL query. A special keyword $Group$ is used to specify that the condition under consideration uses group. A SQL query with the searching criteria is executed using ExecuteNonQuery. The 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 Delete Group Data in Cache Using SQL Query

Before using the feature Delete Group Data in cache using SQL Query, ensure that following prerequisites are fulfilled:

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 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.

// Preconditions: 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 the NCache Management Center 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");

// Precondition: 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 the NCache Management Center or config.ncconf
// Create SQL Query with the specified criteria
// Use the Fully Qualified Name (FQN) of your custom class
String query = "DELETE FROM com.alachisoft.ncache.samples.Customer WHERE $Group$ = ?";

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

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

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

if (rowsAffected == 0) {
    System.out.println("No west coast customers removed");
} else {
    System.out.println(rowsAffected + " West Coast Customers removed");
}

# Precondition: Cache is already connected
# Custom class is query indexed through the the NCache Management Center 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)

// Precondition: Cache is already connected
// This is an async method
// Preconditions: Cache is already connected
// Custom class is query indexed through the the NCache Management Center 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);

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 Query

Prerequisites to Delete Group Data in Cache Using SQL Query

Delete Group

Note

Additional Resources

See Also

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