From 1450a8dd84a5aaac00201d9d06e865fa52c84417 Mon Sep 17 00:00:00 2001
From: Erik Darling <2136037+erikdarlingdata@users.noreply.github.com>
Date: Thu, 19 Feb 2026 18:17:17 -0500
Subject: [PATCH] Fix Query Trace Patterns showing empty despite data existing
 (#168)

The view report.long_running_query_patterns aggregates ALL time then
takes TOP 50 by avg_duration_ms. When recent patterns are shorter than
old load test patterns, the dashboard's time filter eliminates all 50
rows. Fix by inlining the query with time filter inside the CTE so
aggregation only considers data within the selected time range.

The second part of #168 (Trace Analysis in wrong location) was already
fixed in PR #175.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 .../DatabaseService.QueryPerformance.cs       | 101 ++++++++++--------
 1 file changed, 58 insertions(+), 43 deletions(-)

diff --git a/Dashboard/Services/DatabaseService.QueryPerformance.cs b/Dashboard/Services/DatabaseService.QueryPerformance.cs
index 26cd0d17..1d930bbd 100644
--- a/Dashboard/Services/DatabaseService.QueryPerformance.cs
+++ b/Dashboard/Services/DatabaseService.QueryPerformance.cs
@@ -1248,51 +1248,66 @@ public async Task<List<LongRunningQueryPatternItem>> GetLongRunningQueryPatterns
                     await using var tc = await OpenThrottledConnectionAsync();
                     var connection = tc.Connection;
         
-                    string query;
-                    if (fromDate.HasValue && toDate.HasValue)
-                    {
-                        query = @"
-        SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
-
-        SELECT
-            lrqp.database_name,
-            lrqp.query_pattern,
-            lrqp.executions,
-            lrqp.avg_duration_sec,
-            lrqp.max_duration_sec,
-            lrqp.avg_cpu_sec,
-            lrqp.avg_reads,
-            lrqp.avg_writes,
-            lrqp.concern_level,
-            lrqp.recommendation,
-            lrqp.sample_query_text,
-            lrqp.last_execution
-        FROM report.long_running_query_patterns AS lrqp
-        WHERE lrqp.last_execution >= @from_date AND lrqp.last_execution <= @to_date
-        ORDER BY lrqp.last_execution DESC;";
-                    }
-                    else
-                    {
-                        query = @"
+                    /* Inline the aggregation with time-bounded CTE instead of using the view.
+                       The view aggregates ALL time then takes TOP 50 by avg_duration, which causes
+                       the dashboard's time filter to find zero matches when recent patterns are
+                       shorter-running than old load test patterns (GitHub issue #168). */
+                    string timeFilter = fromDate.HasValue && toDate.HasValue
+                        ? "ta.end_time >= @from_date AND ta.end_time <= @to_date"
+                        : "ta.end_time >= DATEADD(HOUR, @hours_back, SYSDATETIME())";
+
+                    string query = $@"
         SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
 
-        SELECT
-            lrqp.database_name,
-            lrqp.query_pattern,
-            lrqp.executions,
-            lrqp.avg_duration_sec,
-            lrqp.max_duration_sec,
-            lrqp.avg_cpu_sec,
-            lrqp.avg_reads,
-            lrqp.avg_writes,
-            lrqp.concern_level,
-            lrqp.recommendation,
-            lrqp.sample_query_text,
-            lrqp.last_execution
-        FROM report.long_running_query_patterns AS lrqp
-        WHERE lrqp.last_execution >= DATEADD(HOUR, @hours_back, SYSDATETIME())
-        ORDER BY lrqp.last_execution DESC;";
-                    }
+        WITH
+            query_patterns AS
+        (
+            SELECT
+                ta.database_name,
+                query_pattern = LEFT(ta.sql_text, 200),
+                executions = COUNT_BIG(*),
+                avg_duration_ms = AVG(ta.duration_ms),
+                max_duration_ms = MAX(ta.duration_ms),
+                avg_cpu_ms = AVG(ta.cpu_ms),
+                avg_reads = AVG(ta.reads),
+                avg_writes = AVG(ta.writes),
+                sample_query_text = MAX(ta.sql_text),
+                last_execution = MAX(ta.end_time)
+            FROM collect.trace_analysis AS ta
+            WHERE {timeFilter}
+            GROUP BY
+                ta.database_name,
+                LEFT(ta.sql_text, 200)
+        )
+        SELECT TOP (50)
+            database_name,
+            query_pattern,
+            executions,
+            avg_duration_sec = avg_duration_ms / 1000.0,
+            max_duration_sec = max_duration_ms / 1000.0,
+            avg_cpu_sec = avg_cpu_ms / 1000.0,
+            avg_reads,
+            avg_writes,
+            concern_level =
+                CASE
+                    WHEN avg_duration_ms > 60000 THEN N'CRITICAL - Avg > 1 minute'
+                    WHEN avg_duration_ms > 30000 THEN N'HIGH - Avg > 30 seconds'
+                    WHEN avg_duration_ms > 10000 THEN N'MEDIUM - Avg > 10 seconds'
+                    ELSE N'INFO'
+                END,
+            recommendation =
+                CASE
+                    WHEN avg_reads > 1000000 THEN N'High read count - check for missing indexes, table scans'
+                    WHEN avg_cpu_ms > avg_duration_ms * 0.8 THEN N'CPU-bound query - check for complex calculations, functions'
+                    WHEN avg_writes > 100000 THEN N'High write volume - review update/delete patterns'
+                    ELSE N'Review execution plan for optimization opportunities'
+                END,
+            sample_query_text = CONVERT(nvarchar(500), sample_query_text),
+            last_execution
+        FROM query_patterns
+        WHERE executions > 1
+        ORDER BY
+            avg_duration_ms DESC;";
         
                     using var command = new SqlCommand(query, connection);
                     command.CommandTimeout = 120;