Batch delete cause deadlock error

Question

Hi experts,
I have a custom web part that has to delete a create hundreds of items in a list containing about 20,000 items.
The web part worked fine for about one year, but last week something went wrong and the customer had an error.
In the SharePoint logs I found a TimeOut error message, so I thought to the delete algortihm.
In fact, the delete part in the web part was very easy: first I look for the items to delete, with a CAML query, then I have something like this:
SPListItemCollection items = myList.GetItems(query);
for (int i = 0; i < items.Count; i++)
      SPListItem item = items[i];
      myList.GetItemByUniqueId(item.UniqueId).Delete();
So I tried to improve it, by using Batch delete.
The new code looks like this:
HashSet<int> idsToDelete = /* Load IDs of elements I have to delete with CAML query */
StringBuilder delete = new StringBuilder();
delete.Append("<?xml version=\"1.0\" encoding=\"UTF-8\"?><Batch>");
foreach (int itemId in idsToDelete)
       delete.Append("<Method>");
       delete.Append("<SetList Scope=\"Request\">" + myList.ID + "</SetList>");
       delete.AppendFormat("<SetVar Name=\"ID\">{0}</SetVar>", itemId);
       delete.Append("<SetVar Name=\"Cmd\">Delete</SetVar>");
       delete.Append("</Method>");
delete.Append("</Batch>");
SPContext.Current.Site.RootWeb.ProcessBatchData(delete.ToString());
Unfortunately, it seems there is something wrong: in fact, when I try to execute the web part, I got an error and in the SharePoint logs 
I found a very long list of the following error message:
Unknown SQL Exception 1205 occurred. Additional error information from SQL Server is included below.  Transaction (Process ID 111) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.
What I am doing wrong??
Is there someone who can help?
Thank you very much.
Regards,
Gennaro

Answer 1

Hi Gennaro,
If you want to bulk delete list items, we can use PowerShell to achieve it.
Create a query and it is limited to returning 2000 items at a time, and uses the ListItemCollectionPosition property to continue retrieving items in batches of 2000 until all the items have been queried.
$itemCount = 0;
$listId = $list.ID;
[System.Text.StringBuilder]$batchXml = New-Object "System.Text.StringBuilder";
$batchXml.Append("<?xml version='"1.0'" encoding='"UTF-8'"?><batch>");
$command = [System.String]::Format( "<method><setlist>{0}</setlist><setvar name='"ID'">{1}</setvar><setvar name='"Cmd'">Delete</setvar></method>", $listId, "{0}" );
do
$listItems = $list.GetItems($query)
$query.ListItemCollectionPosition = $listItems.ListItemCollectionPosition
foreach ($item in $listItems)
if($item -ne $null){$batchXml.Append([System.String]::Format($command, $item.ID.ToString())) | Out-Null;$itemCount++;}
while ($query.ListItemCollectionPosition -ne $null)
$batchXml.Append("</batch>");
$itemCount;
More information is here:
http://matthewyarlett.blogspot.com/2013/07/well-that-was-fun-bulk-deleting-items.html
Best Regards
TechNet Community Support
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