Search Group Data in Cache with SQL Query [Deprecated]
NCache provides object queries through which you can use 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. The 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 the ICacheReader type of instance.
Prerequisites
Before using the NCache Client-side APIs, ensure that the following prerequisites are fulfilled:
- Add the following Maven dependencies for your Java client application in
pom.xml file:
<dependency>
<groupId>com.alachisoft.ncache</groupId>
<!--for NCache Enterprise-->
<artifactId>ncache-client</artifactId>
<version>x.x.x</version>
</dependency>
- Install the following packages in your Python client application:
- Import the following packages in your application:
- The cache must be running.
- Make sure that the data being added is serializable.
- Custom classes/searchable attributes must be indexed as explained in Configuring Query Indexes.
- For API details, refer to: Cache, execute_reader, get_search_service, QueryCommand.
Warning
If the searched group is not in the cache, the query will be returned as a Null value.
Search for Data in Groups using SQL Query
You can also search for the cache items present in groups through SQL. The following program searches for Customer IDs present in a group through SQL query.
try
{
// Precondition: Cache is already connected
// A user wants to see all the West Coast Customers using the SQL query.
// Items with groups exist in the cache
// Custom class is query indexed through the NCache Management Center or config.ncconf
// Create an SQL Query with the specified criteria
// Make sure to use the Fully Qualified Name (FQN)
string query = "SELECT CustomerID, ContactName FROM FQN.Customer WHERE $Group$ = ?";
// Use QueryCommand for query execution
var queryCommand = new QueryCommand(query);
// Providing parameters for query
queryCommand.Parameters.Add("$Group$", "West Coast Customers");
// Executing the Query
ICacheReader reader = cache.SearchService.ExecuteReader(queryCommand);
// Read results if result set is not empty
if (reader.FieldCount > 0)
{
while (reader.Read())
{
// Get the value of the result set
string customerID = reader.GetValue<string>("CustomerID");
string customerName = reader.GetValue<string>("ContactName");
Console.WriteLine($"Customer '{customerName}' having ID '{customerID}' belongs to West Coast.");
}
}
else
{
Console.WriteLine($"No customers from West Coast found");
}
}
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
}
try
{
// Precondition: Cache is already connected
// A user wants to see all the West Coast Customers using the SQL query.
// Items with groups exist in the cache
// Custom class is query indexed through the NCache Management Center or config.ncconf
// Create an SQL Query with the specified criteria
// Make sure to use the Fully Qualified Name (FQN)
String query = "SELECT customerID, contactName FROM FQN.Customer WHERE $Group$ = ?";
// Use QueryCommand for query execution
QueryCommand queryCommand = new QueryCommand(query);
// Providing parameters for query
queryCommand.getParameters().put("$Group$", "West Coast Customers");
// Executing the Query
CacheReader reader = cache.getSearchService().executeReader(queryCommand);
// Read results if result set is not empty
if (reader.getFieldCount() > 0)
{
while (reader.read())
{
// Get the value of the result set
String customerID = reader.getValue("customerID", String.class);
String customerName = reader.getValue("contactName", String.class);
System.out.println("Customer '" + customerName + "' having ID '" + customerID + "' belongs to West Coast.");
}
}
else
{
System.out.println("No customers from West Coast found");
}
}
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:
# Precondition: Cache is already connected
# A user wants to see all the West Coast Customers using the SQL query.
# Items with groups exist in the cache
# Custom class is query indexed through the NCache Management Center or config.ncconf
# Create an SQL Query with the specified criteria
# Make sure to use the Fully Qualified Name (FQN)
query = "SELECT CustomerID, ContactName FROM FQN.Customer WHERE $Group$ = ?"
# Use QueryCommand for query execution
query_command = QueryCommand(query)
# Providing parameters for query
query_command.set_parameters({"$Group$": group_name})
# Executing the Query
search_service = cache.get_search_service()
cache_reader = search_service.execute_reader(query_command)
# Read results if result set is not empty
if cache_reader.get_field_count() > 0:
while cache_reader.read():
# Get the value of the result set
customer_id = cache_reader.get_value("CustomerID")
customer_name = cache_reader.get_value("ContactName")
print(f"Customer '{customer_name}' having ID '{customer_id}' belongs to West Coast.")
else:
print("No customers from West Coast found")
except Exception as error:
# Exception can occur due to:
# Connection Failures
# Operation Timeout
# Operation during state transfer
print("An error occurred:", str(error))
try
{
// Precondition: Cache is already connected
// This is an async method
// A user wants to see all the West Coast Customers using the SQL query.
// Items with groups exist in the cache
// Custom class is query indexed through the NCache Management Center or config.ncconf
// Provide the Fully Qualified Name (FQN) of your custom class
const query = "SELECT CustomerID, ContactName FFROM FQN.Customer WHERE $Group$ = ?";
// Use QueryCommand for query execution
const queryCommand = new QueryCommand(query);
// Providing parameters for query
const parameters = new Map();
parameters.set("$Group$", "West Coast Customers");
queryCommand.setParameters(parameters);
// Executing the Query
const searchService = await cache.getSearchService();
const cacheReader = await searchService.executeReader(queryCommand);
// Read results if result set is not empty
if (cacheReader.getFieldCount() > 0)
{
while (await cacheReader.read())
{
// Get the value of the result set
const customerID = cacheReader.getValue("CustomerID");
const customerName = cacheReader.getValue("ContactName");
console.log(`Customer '${customerName}' having ID '${customerID}' belongs to West Coast.`
);
}
}
else
{
console.log("No customers from West Coast found");
}
}
catch(error)
{
// 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.
Additional Resources
NCache provides sample application for Groups on GitHub.
See Also
.NET: Alachisoft.NCache.Client namespace.
Java: com.alachisoft.ncache.client namespace.
Python: ncache.client class.
Node.js: Cache class.
