How can I shred this Extended Events XML as fast as possible?

I created an Extended Events session in SQL Server 2008 R2. The session runs, and collects events as they happen, exactly like you'd expect.

If I shred the xml when there are relatively few events, performance is acceptable. When I have thousands of events, it takes for ever to shred the xml.

I know I am doing something wrong, I just don't have enough knowledge about the internals of the XML engine to understand what.

This is the definition of my Extended Events session:

```
IF EXISTS
(
SELECT 1
FROM sys.server_event_sessions dxs
WHERE dxs.name = 'queries'
)
BEGIN
IF EXISTS (
SELECT 1
FROM sys.dm_xe_sessions dxs
WHERE dxs.name = 'queries'
)
BEGIN
ALTER EVENT SESSION queries ON SERVER STATE = STOP;
END
DROP EVENT SESSION queries ON SERVER;
END

CREATE EVENT SESSION queries ON SERVER
ADD EVENT sqlserver.sql_statement_starting
(
ACTION
(
package0.collect_system_time
--, package0.event_sequence
, sqlserver.client_app_name
, sqlserver.client_hostname
--, sqlserver.database_name
, sqlserver.plan_handle
, sqlserver.sql_text
, sqlserver.username
)
WHERE sqlserver.username = N''
AND sqlserver.database_id = 6 / specific database /
AND sqlserver.client_hostname <> ''
)
, ADD EVENT sqlserver.error_reported
(
ACTION
(
package0.collect_system_time
, sqlserver.client_app_name
, sqlserver.client_hostname
, sqlserver.plan_handle
, sqlserver.sql_text
, sqlserver.username
)
WHERE sqlserver.username <> N''
/ fluff errors below /
AND error <> 5703 / Changed language setting to %.ls. */
AND error <> 5701 / Changed database context to '%.ls'. */
AND error <> 2528 / DBCC execution completed. If DBCC printed error messages, contact your system administrator. /
AND error <> 7969 /* No active open transactio

Thanks to @Tom V for identifying this blog post that identifies the need for a temporary table.

Adapting the ideas in the blog post, this now works very quickly:

/***************************

shred the Event Data into readable form

***************************/

DECLARE @xml XML;

SELECT TOP(1) @xml = CONVERT(xml, xet.target_data)
FROM sys.dm_xe_session_targets AS xet
    INNER JOIN sys.dm_xe_sessions AS xe ON (xe.address = xet.event_session_address)
WHERE xe.name = 'queries';

IF OBJECT_ID('tempdb..#xmlResults') IS NOT NULL
DROP TABLE #xmlResults;

CREATE TABLE #xmlResults
(
    RowNum INT NOT NULL
        PRIMARY KEY CLUSTERED
        IDENTITY(1,1)
    , xeXML XML NOT NULL
);

INSERT INTO #xmlResults (xeXML)
SELECT xm.s.query('.')
FROM @xml.nodes('/RingBufferTarget/event') AS xm(s)
OPTION (Optimize FOR (@xml = Null)); -- Useful for SQL 2008

SELECT *
FROM #xmlResults

SELECT t.EventName
    , DateStamp = DATEADD(HOUR, -6, t.EventDateStamp)
    , DatabaseName = d.name
    , t.ErrorNumber
    , t.ErrorSeverity
    , t.ErrorState
    , t.ErrorMessage
    , t.CollectSystemTime
    , t.ClientAppName
    , t.ClientHostName
    , t.PlanHandle
    , t.SqlText
    , t.UserName
FROM (
        SELECT EventName =          xeXML.value('(event/@name)[1]','varchar(500)')
            , EventDateStamp =      xeXML.value('(event/@timestamp)[1]','datetime')
            , DatabaseID =          xeXML.value('(event/data[(@name)[1] eq "source_database_id"]/value/text())[1]','varchar(255)')
            , ErrorNumber =         xeXML.value('(event/data[(@name)[1] eq "error"]/value/text())[1]','varchar(255)')
            , ErrorSeverity =       xeXML.value('(event/data[(@name)[1] eq "severity"]/value/text())[1]','varchar(255)')
            , ErrorState =          xeXML.value('(event/data[(@name)[1] eq "state"]/value/text())[1]','varchar(255)')
            , ErrorMessage =        xeXML.value('(event/data[(@name)[1] eq "message"]/value/text())[1]','varchar(255)')
            , CollectSystemTime =   xeXML.value('(event/action[(@name)[1] eq "collect_system_time"]/text/text())[1]','varchar(255)')
            , ClientAppName =       xeXML.value('(event/action[(@name)[1] eq "client_app_name"]/value/text())[1]','varchar(255)')
            , ClientHostName =      xeXML.value('(event/action[(@name)[1] eq "client_hostname"]/value/text())[1]','varchar(255)')
            , PlanHandle = CONVERT(xml, xeXML.value('(event/action[(@name)[1] eq "plan_handle"]/value/text())[1]','varchar(255)')).value('(plan/@handle)[1]', 'varchar(255)')
            , SqlText =             xeXML.value('(event/action[(@name)[1] eq "sql_text"]/value/text())[1]','nvarchar(max)')
            , UserName =            xeXML.value('(event/action[(@name)[1] eq "username"]/value/text())[1]','varchar(128)')
        FROM #xmlResults xm
    ) t
    LEFT JOIN sys.databases d ON t.DatabaseID = d.database_id
ORDER BY t.UserName
    , t.EventDateStamp;

StackExchange Database Administrators Q#121491, answer score: 12