-- ===================================================================================================================
-- Collector: DeadlockCollector ("deadlocks")
-- ===================================================================================================================
-- Hvad:        Nye deadlock-grafer (xml_deadlock_report) fra den indbyggede system_health-session.
-- Fil:         src/SQLInsight.Collectors/Concurrency/DeadlockCollector.cs
-- Interval:    5 min som standard (SQLInsight:CollectorIntervals:deadlocks)
-- Versioner:   SQL Server 2008 og nyere (filer fra 2012, ellers ring buffer)
--
-- Rettigheder til agentens login (se db/permissions/grant-least-privilege.sql; [agent] = agentens login):
--   GRANT VIEW SERVER STATE TO [agent];                -- SQL Server 2005-2019
--   GRANT VIEW SERVER PERFORMANCE STATE TO [agent];    -- SQL Server 2022+ (erstatter VIEW SERVER STATE)
--   GRANT VIEW SERVER SECURITY STATE TO [agent];       -- SQL Server 2022+
--
-- Bruges af:   SQLI-DLK-001
-- Read-only:   Ja: kun SELECT (sys.fn_xe_file_target_read_file og DMV'er) samt SET-sessionsindstillinger. Ingen
--              temp-tabeller; læsepositionen findes med ROW_NUMBER() i samme forespørgsel.
-- Kørsel:     Kør i SSMS som agentens login. Hver variant er sin egen batch (GO); en variant for en anden SQL Server-version
--             end din kan fejle - det er forventet. Agenten kører altid med sessionsindstillingerne i _collectors/InstanceProbe.sql.
-- ===================================================================================================================

-- Variant: SQL Server 2012 og nyere (system_health-filer; første læsning)
-- Kilde: DeadlockCollector.BuildFileSql
-- Kode:  src/SQLInsight.Collectors/Concurrency/DeadlockCollector.cs : DeadlockCollector.BuildFileSql(lastFile: null, lastOffset: null)
SELECT e.event_data, e.file_name, e.file_offset, e.rn
FROM (
    SELECT CASE WHEN object_name = N'xml_deadlock_report' THEN CAST(event_data AS nvarchar(max)) END AS event_data,
           file_name, file_offset,
           ROW_NUMBER() OVER (ORDER BY file_name DESC, file_offset DESC) AS rn
    FROM sys.fn_xe_file_target_read_file(N'system_health*.xel', NULL, NULL, NULL)
) AS e
WHERE e.event_data IS NOT NULL OR e.rn = 1;
GO

-- Variant: SQL Server 2008 – 2008 R2, og når event-filerne ikke kan læses
-- Kilde: DeadlockCollector.RingBufferSql
-- Kode:  src/SQLInsight.Collectors/Concurrency/DeadlockCollector.cs : DeadlockCollector.RingBufferSql
SELECT CAST(t.target_data AS nvarchar(max))
FROM sys.dm_xe_session_targets t
JOIN sys.dm_xe_sessions s ON s.address = t.event_session_address
WHERE s.name = N'system_health' AND t.target_name = N'ring_buffer'
GO