Delete Tag Data from Cache with SQL

Note

This feature is only available in NCache Enterprise Edition.

Object queries can also be used to remove items from cache with your query criteria being tags. Object queries let you search the data in your cache and then delete it.

The idea of a special keyword $Tag$ also exists here. ExecuteNonQuery is used in queries containing delete operations. It returns the number of affected rows after query is executed.

You can remove the items present with a specific tag as explained below.

Prerequisites

Install the following NuGet package in your application:
- Enterprise: Alachisoft.NCache.SDK
Include the following namespace in your application:
The cache must be running.
The application must be connected to cache before performing the operation.
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, ExecuteNonQuery, SearchService
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.

Add the following Maven dependencies in your pom.xml file:

<dependency>
    <groupId>com.alachisoft.ncache</groupId>
    <artifactId>ncache-client</artifactId>
    <version>x.x.x</version>
</dependency>

Include the following packages in your application:
- import com.alachisoft.ncache.client.*;
- import com.alachisoft.ncache.runtime.caching.*;
- import com.alachisoft.ncache.runtime.exceptions.*;
The cache must be running.
The application must be connected to cache before performing the operation.
Custom classes/searchable attributes must be indexed as explained in Configuring Query Indexes.
Make sure that the data be Cache , CacheReader, executeNonQuery, QueryCommand, getSearchService
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.

Install and include the following module in your application:
- Enterprise: const ncache = require('ncache-client')
The cache must be running.
The application must be connected to cache before performing the operation.
Custom classes/searchable attributes must be indexed as explained in Configuring Query Indexes.
For API details refer to: Cache, executeReader, QueryCommand, CacheReader, getSearchService
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.

Install the NCache Python client by executing the following command:

# Enterprise Client
pip install ncache-client

Indexing for searchable objects and their attributes need to be configured first as explained in Configuring Query Indexes in Administrator's Guide.
Import the NCache module in your application.
The cache must be running.
For API details, refer to: Cache, CacheReader, execute_non_query, QueryCommand getSearchService
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.

Add the following Maven dependencies in your pom.xml file:

<dependency>
    <groupId>com.alachisoft.ncache</groupId>
    <artifactId>ncache-scala-client</artifactId>
    <version>x.x.x</version>
</dependency>

Indexing for searchable objects and their attributes need to be configured first as explained in Configuring Query Indexes in Administrator's Guide.
Import the following packages in your application:
- import com.alachisoft.ncache.scala.client.*;
- import com.alachisoft.ncache.scala.runtime.caching.*;
The cache must be running.
The application must be connected to cache before performing the operation.
Make sure that the data being added is serializable.
For API details refer to: Cache, QueryCommand, executeNonQuery, SearchService
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.

SQL DELETE for One Tag

Using object queries, items can be deleted using a single tag. You can SQL delete for a single tag using the older syntax or the new one.

Syntax

Following example deletes all the items associated with the tag West Coast Customers using the SQL query.

try
{
    // Pre-condition: Cache is already connected
    // Make sure to use the Fully Qualified Name (FQN)
    string query = "DELETE FROM Alachisoft.NCache.Samples.Data.
    Customer WHERE $Tag$ = ?";

    // Create query command and add parameter
    var queryCommand = new QueryCommand(query);
    queryCommand.Parameters.Add("$Tag$", "West Coast Customers");

    // Executing Query
    int rowsAffected = cache.SearchService.ExecuteNonQuery
    (queryCommand);

    if (rowsAffected == 0)
     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
{
    // Pre-condition: Cache is already connected
    // Items are already present in the cache with tags
    // Custom class is query indexed through NCache Web Manager or config.ncconf

    // Make sure to use the Fully Qualified Name (FQN)
    String query = "DELETE FROM FQN.Customer WHERE $Tag$ = ?";

    // Use QueryCommand for query execution
    QueryCommand queryCommand = new QueryCommand(query);
    queryCommand.getParameters().put("$Tag$", "Important Customers");

    // 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 IllegalArgumentException or NullPointerException  
}

// This is an async method
try
{
    // Pre-condition: Cache is already connected
    // Items are already present in the cache with tags
    // Custom class is query indexed through NCache Web Manager or config.ncconf

    // Make sure to use the Fully Qualified Name (FQN)
    var query = "DELETE FROM FQN.Customer WHERE $Tag$ = ?";

    // Use QueryCommand for query execution
    var queryCommand = new ncache.QueryCommand(query);
    queryCommand.getParameters().set("$Tag$", "Important Customers");

    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-condition: Cache is already connected
    # Items are already present in the cache with tags
    # Custom class is query indexed through NCache Web Manager or config.ncconf

    # Make sure to use the Fully Qualified Name(FQN)
    query = "DELETE FROM FQN.Customer WHERE $Tag$ = ?"

    # Use QueryCommand for query execution
    query_command = ncache.QueryCommand(query)
    query_command.set_parameters({"$Tag$": "Important Customers"})

    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

try {
    // Pre-condition: Cache is already connected
    // Items are already present in the cache with tags
    // Custom class is query indexed through NCache Web Manager or config.ncconf

    // Make sure to use the Fully Qualified Name (FQN)
    val query = "DELETE FROM FQN.Customer WHERE $Tag$ = ?"

    // Use QueryCommand for query execution
    val queryCommand = new QueryCommand(query)
    queryCommand.setParameters(Map("$Tag$" -> "Important Customers"))

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

Warning

Providing Null tag value for the query will throw an ArgumentNullException or NullPointerException.

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 Tags on GitHub.

Delete Tag Data from Cache with SQL

Note

Prerequisites

SQL DELETE for One Tag

Syntax

Warning

Note

Additional Resources

See Also