Search Group Data in Cache with SQL

Note

This feature is only available in NCache Enterprise Edition.

NCache provides object queries through which you use a criteria given in a query to search result sets. To retrieve the data 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 ExecuteReader.

ExecuteReader processes the query on the server side and then sends the result in chunks (as a dictionary containing keys and values) to the client in the tabular form to ICacheReader type of instance.

Pre-Requisites

  • Install the following NuGet package in your application.
  • Include the following namespaces in your application:
    • Alachisoft.NCache.Client
    • Alachisoft.NCache.Runtime
  • The application must be connected to cache before performing the operation.
  • Cache must be running.
  • Custom classes/searchable attributes must be indexed as explained in Configuring Query Indexes.
  • Make sure that the data being added is serializable.
  • For API details refer to: ICache, ICacheReader, QueryCommand, ExecuteReader
  • To ensure the operation is fail safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.
  • To handle any unseen exceptions, refer to the Troubleshooting section.
Warning

If the searched group is not in the cache, the query will be returned as Null.

Search for Group

Given a certain criteria, you can search for groups present in the cache with SQL queries. The following program searches for a group against a certain Customer ID through SQL query i.e. the group that the Customer ID belongs to.

try
{
    // Pre-conditions: Cache is already connected
    // Items with groups exist in cache
    // Custom class is query indexed through NCache Web Manager or config.ncconf

    // Search for items with group
    // Provide Fully Qualified Name (FQN) of your custom class 
    string query = "SELECT $Group$ FROM FQN.Customer WHERE CustomerName = ?";

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

    // Providing parameters for query
    queryCommand.Parameters.Add("CustomerName", "John Smith");

    // Executing QueryCommand through ICacheReader
    ICacheReader cacheReader = cache.SearchService.ExecuteReader(queryCommand);

    // Check if the result set is not empty
    if (cacheReader.FieldCount > 0)
    {
        while (cacheReader.Read())
        {
           // Perform operations
            string groupName = cacheReader.GetValue<string>(1);                   
        }
    }
    else
    {
        // Null query result set retrieved
    }
}
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 generic exception like ArgumentException, ArgumentNullException
}

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

Search for Data in Groups

You can also search for cache items present in groups through SQL. The following program searches for Customer IDs present in a group through SQL query.

try
{
    // Pre-conditions: Cache is already connected
    // Items with groups exist in cache
    // Custom class is query indexed through NCache Web Manager or config.ncconf

    // Search for items with group
    // Provide Fully Qualified Name (FQN) of your custom class 
    string query = "SELECT CustomerID FROM FQN.Customer WHERE $Group$ = ?";

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

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

    // Executing QueryCommand through ICacheReader
    ICacheReader reader = cache.SearchService.ExecuteReader(queryCommand);

    // Check if the result set is not empty
    if (reader.FieldCount > 0)
    {
        while (reader.Read())
        {
            string CustomerID = reader.GetValue<string>(1);
            // Perform operations
        }
    }
    else
    {
        // Null query result set retrieved
    }
}
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 generic exception like ArgumentException, ArgumentNullException    
}

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

Additional Resources

NCache provides sample application for Groups on GitHub.

See Also

Add/Update Cache Data with Groups
Retrieve Cache Data with Groups
Remove Cache Data with Group
Use Groups for Logical Data Grouping
Delete Group Data in Cache with SQL