Delete items from large Lists

Situation:

We have a large list (more than 100.000 items). The request is to delete all the items.

Solution:

We can try to iterate through all items and delete. Of course this approach will generate performance problems. The best solution I found is to use a batch:

private void ClearList(SPList taskList)        
{                      
    StringBuilder sbDelete = BuildBatchDeleteCommand(taskList);            
    taskList.ParentWeb.ProcessBatchData(sbDelete.ToString());                  
}        

/// <summary>        
/// Builds a batch string with a list of all the items that are to be deleted.        
/// </summary>        
/// <param name="spList"></param>        
/// <returns></returns>        
private static StringBuilder BuildBatchDeleteCommand(SPList spList)        
{            
    StringBuilder sbDelete = new StringBuilder();            
    sbDelete.Append("<?xml version=\"1.0\" encoding=\"UTF-8\"?><Batch>");            
    string command = "<Method><SetList Scope=\"Request\">" + spList.ID + 
                "</SetList><SetVar Name=\"ID\">{0}</SetVar><SetVar Name=\"Cmd\">Delete</SetVar></Method>";            
    foreach (SPListItem item in spList.Items)            
    {                
        sbDelete.Append(string.Format(command, item.ID.ToString()));            
    }            
    sbDelete.Append("</Batch>");           
    return sbDelete;        
}

 
More details on how to use batch : http://msdn.microsoft.com/en-us/library/cc404818.aspx