Plan değişimi P437

(@BatchSize int,@LeaseSeconds int)WITH c AS (
        SELECT TOP (@BatchSize) *
        FROM rag.EmbedQueue WITH (READPAST, UPDLOCK, ROWLOCK)
        WHERE Status = 'Queued' OR (Status = 'Running' AND LeaseUntilUtc < DBA.fn_Now())
        -- Vaka/KB önce: bekçi her gün binlerce profili kuyruğa alır, onaydan sonra gelen vaka onların ardında beklemesin
        ORDER BY CASE SourceType WHEN 'Profile' THEN 1 ELSE 0 END, QueueID
    )
    UPDATE c SET Status = 'Running', Attempt = Attempt + 1, LeaseUntilUtc = DATEADD(second, @LeaseSeconds, DBA.fn_Now())
    OUTPUT inserted.QueueID, inserted.SourceType, inserted.SourceRef, inserted.Attempt

Plan change case #P437 | DB: DB-11 | Improvement | Confidence: Medium (review pending)
Query: (@BatchSize int,@LeaseSeconds int)WITH c AS ( SELECT TOP (@BatchSize) * FROM rag.EmbedQueue WITH (READPAST, UPDLOCK, ROWLOCK) WHERE Status = ? OR (Status = ? AND LeaseUntilUtc < DBA.fn_Now()) ORDER BY CASE SourceType WHEN ? THEN ? ELSE ? END, QueueID ) UPDATE c SET Status = ?, Attempt = Attempt + ?, LeaseUntilUtc = DATEADD(second, @LeaseSeconds, DBA.fn_Now()) OUTPUT inserted.QueueID, inserted.SourceType, inserted.SourceRef, inserted.Attempt
Change: 2026-10-06 06:00 UTC, plan 64598 → 64696, pattern: Transition
Impact (Query Store, per execution): duration 15.3 → 0.5 ms (-97%); CPU 15.2 → 0.5 ms (-97%); reads 1,258 → 200 (-84%); rows 4.91 → 0.34 (-93%)
Plan difference: Access only in the old plan: rag.EmbedQueue Clustered Index Scan [PK_EmbedQueue]; Access only in the new plan: rag.EmbedQueue Index Seek [IX_EmbedQueue_Status]; rag.EmbedQueue Clustered Index Seek [PK_EmbedQueue] (lookup); Join only in the new plan: Nested Loops (Inner Join) ×2; Estimated cost: 0.942 → 0.195; estimated rows: 100 → 20
Candidate cause: STATS — Statistic rag.EmbedQueue.PK_EmbedQueue was updated 2026-10-05 21:01 (sampled 100%); 4 updates in the window; the plans use this statistic.
Candidate cause: STATS — Statistic rag.EmbedQueue.IX_EmbedQueue_Status was updated 2026-10-06 00:17 (sampled 100%); 3 updates in the window; the plans use this statistic.
Candidate cause: STATS — Statistic rag.EmbedQueue.UX_EmbedQueue_Pending was updated 2026-10-05 20:20 (sampled 100%); 2 updates in the window; the plans use this statistic.
Candidate cause: WORKLOAD — The plans see a different workload: rows per execution 4.91 → 0.34. The plans may have been compiled for different parameters or batch sizes.
Counter-evidence: HIGH_VARIANCE — The new plan's duration standard deviation is 548% of the average: the average is not reliable.
Confidence rationale: Medium: more than one candidate (STATS, WORKLOAD) — competing explanations. Weak counter-evidence: HIGH_VARIANCE.
Note: this is a candidate cause, not proof of the root cause.