Improve Query Store grid query performance (#143)#144
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erikdarlingdata merged 1 commit intodevfrom Mar 25, 2026
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Three changes from community feedback (41s → 3s on slow machines): 1. Remove WHERE p.query_plan IS NOT NULL from the ranked CTE — this predicate on nvarchar(max) causes an expensive implicit conversion scan. NULL plans are already handled by the C# reader (skip row). 2. Two-phase approach: materialize TOP N into #top_plans first using only numeric columns, then join to query_text/plan XML tables for just the winners. Avoids dragging expensive nvarchar(max) columns through the entire CTE evaluation. 3. Remove OPTION (LOOP JOIN) — reported 3x faster without it on multiple test environments. Tested on SQL2022 with PerformanceMonitor Query Store data. Closes #143 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This was referenced Mar 25, 2026
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Summary
Community-reported performance fix — 41s → 3s on slow machines / cloud instances.
Three changes based on issue #143 by @rferraton:
Remove
WHERE p.query_plan IS NOT NULLfrom the ranked CTE — predicate onnvarchar(max)causes an expensive implicit conversion scan. NULL plans are already handled by the C# reader (row is skipped).Two-phase temp table approach — materialize TOP N into
#top_plansusing only numeric columns, then join toquery_text/plan XMLtables for just the winners. Avoids dragging expensivenvarchar(max)columns through the entire CTE.Remove
OPTION (LOOP JOIN)— reported 3x faster without it across multiple environments.Filter clauses (
query_id,query_hash,plan_hash,module_name) remain in the final SELECT whereq.*/p.*are available.Test plan
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