Summary

• Query store collector fetches only new runtime_stats intervals since last collection instead of scanning 60-min window with CTE/GROUP BY every cycle
• CPU collector deduplicates ring buffer samples client-side (~1 row/cycle instead of 60)
• Deadlock collector moves XML parsing out of DuckDB timing block for accurate metrics
• Shared GetLastCollectedTimeAsync helper extracts watermark lookup pattern

Test plan

• dotnet build -c Debug — 0 warnings, 0 errors
• Launch Lite, connect to sql2022, watch collection_log timings over 2-3 cycles
• Verify query_store SQL timing drops from ~2300ms to ~100-200ms
• Verify cpu_utilization inserts ~1 row/cycle instead of 60
• Verify deadlock DuckDB timing drops from ~677ms to single-digit ms

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