Configure Searchable Attributes for Data Structures in Cache

NCache allows you to organize distributed data structures, such as HashSets, Lists, and Queues, by associating them with searchable metadata. A data structure can be associated with searchable attributes such as:

These searchable attributes can be used to query all associated items, as explained in Querying Data Structures. For example, a CacheItem and HashSet can belong to the same group. These attributes are specified using the DataTypeAttributes class.

Important

These attributes cannot be modified once a data structure is created. However, the data structure itself can be modified.

Prerequisites

Before using the NCache client-side APIs, ensure that the following prerequisites are fulfilled:

The following code sample creates a HashSet ProductIDSet of int type and specifies Group Electronics, Tags and a Named Tag to it using DataTypeAttributes. The ProductIDs are then fetched and added to this HashSet. You can also query on these set values.

Tip

One quick way to verify whether a data structure has been created is to use either properties of the Cache class:

  • Count returns the number of items present in the cache.
  • Contains verifies if the specified key of the data structure exists in the cache.
try
{
  // Precondition: Cache is already connected

  // Specify unique cache key for set
  string key = "ProductIDSet";

  // Specify attributes for HashSet
  var attributes = new DataTypeAttributes();

  // Specify group "Electronics"
  attributes.Group = "Electronics";

  // Specify tags
  Tag[] tags = new Tag[2];
  tags[0] = new Tag("2 Year Warranty");
  tags[1] = new Tag("Stainless Steel");
  attributes.Tags = tags;

  // Specify Named Tag
  var namedTag = new NamedTagsDictionary();
  namedTag.Add("Discount", 0.4);
  attributes.NamedTags = namedTag;

  // Create HashSet with attributes
  IDistributedHashSet<int> hashSet = cache.DataTypeManager.CreateHashSet<int>(key, attributes);

  // Adding Product IDs to HashSet
  int[] productIDs = FetchProductIDs();
  foreach(var productID in productIDs)
  {
      // Add product IDs to HashSet
      hashSet.Add(productID);
  }
  // You can also query on this HashSet using these attributes
}
catch (OperationFailedException ex)
{
    // NCache specific exception
    if(ex.ErrorCode == NCacheErrorCodes.KEY_ALREADY_EXISTS)
    {
        // An item with the same key already exists
    }
    else if (ex.ErrorCode == NCacheErrorCodes.CACHEITEM_IN_DATA_STRUCTURES)
    {
        // Data structures cannot be of CacheItem type
        // CacheItems cannot be added in data structures
    }
    else
    {
        // NCache specific exception
        // Exception can occur due to:
        // Connection Failures
        // Operation Timeout
        // Operation performed during state transfer
    }
}
catch (Exception ex)
{
    // Any generic exception like ArgumentNullException or ArgumentException
}
Note

To ensure that 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 a sample application for configuring searchable attributes with data structures on GitHub.

See Also

.NET: Alachisoft.NCache.Client.DataTypes namespace
Java: com.alachisoft.ncache.client.datastructures namespace
Node.js: DataStructureManager class