Optimize usage dashboard: partial indexes, request cache, parallel histograms

- Add migration 14: partial covering indexes WHERE job_state='running'
  for user/project/subcluster groupings (tiny B-tree vs full table)
- Inline literal state value in BuildWhereClause so SQLite matches
  partial indexes instead of parameterized placeholders
- Add per-request statsGroupCache (sync.Once per filter+groupBy key)
  so identical grouped stats queries execute only once per GQL operation
- Parallelize 4 histogram queries in AddHistograms using errgroup
- Consolidate frontend from 6 GQL aliases to 2, sort+slice top-10
  client-side via $derived

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Entire-Checkpoint: 5b26a6e5ff10

internal/repository/jobQuery.go

@@ -198,8 +198,10 @@ func BuildWhereClause(filter *model.JobFilter, query sq.SelectBuilder) sq.Select
 	}
 	if filter.State != nil {
 		if len(filter.State) == 1 {
+			// Inline literal value so SQLite can match partial indexes (WHERE job_state = 'running').
+			// Safe: values come from validated GraphQL enum (model.JobState).
 			singleStat := string(filter.State[0])
-			query = query.Where("job.job_state = ?", singleStat)
+			query = query.Where(fmt.Sprintf("job.job_state = '%s'", singleStat))
 		} else {
 			states := make([]string, len(filter.State))
 			for i, val := range filter.State {

internal/repository/migration.go

@@ -21,13 +21,14 @@ import (
 // is added to internal/repository/migrations/sqlite3/.
 //
 // Version history:
+//   - Version 14: Partial covering indexes for running jobs (tiny B-tree vs millions)
 //   - Version 13: Add covering indexes for status/dashboard queries (cluster, job_state, ...)
 //   - Version 12: Add covering index for stats queries (cluster, start_time, hpc_user, ...)
 //   - Version 11: Optimize job table indexes (reduce from ~78 to 48)
 //   - Version 10: Node table
 //
 // Migration files are embedded at build time from the migrations directory.
-const Version uint = 13
+const Version uint = 14
 
 //go:embed migrations/*
 var migrationFiles embed.FS

internal/repository/migrations/sqlite3/14_running-partial-indexes.down.sql

@@ -0,0 +1,5 @@
+-- Reverse migration 14: Drop partial indexes for running jobs
+
+DROP INDEX IF EXISTS jobs_running_user_stats;
+DROP INDEX IF EXISTS jobs_running_project_stats;
+DROP INDEX IF EXISTS jobs_running_subcluster_stats;

internal/repository/migrations/sqlite3/14_running-partial-indexes.up.sql

@@ -0,0 +1,18 @@
+-- Migration 14: Partial covering indexes for running jobs
+-- Only running jobs are in the B-tree, so these indexes are tiny compared to
+-- the full-table indexes from migration 13. SQLite uses them when the query
+-- contains the literal `job_state = 'running'` (not a parameter placeholder).
+
+CREATE INDEX IF NOT EXISTS jobs_running_user_stats
+  ON job (cluster, hpc_user, num_nodes, num_hwthreads, num_acc, duration, start_time)
+  WHERE job_state = 'running';
+
+CREATE INDEX IF NOT EXISTS jobs_running_project_stats
+  ON job (cluster, project, num_nodes, num_hwthreads, num_acc, duration, start_time)
+  WHERE job_state = 'running';
+
+CREATE INDEX IF NOT EXISTS jobs_running_subcluster_stats
+  ON job (cluster, subcluster, num_nodes, num_hwthreads, num_acc, duration, start_time)
+  WHERE job_state = 'running';
+
+PRAGMA optimize;

internal/repository/stats.go

@@ -55,6 +55,7 @@ import (
 	cclog "github.com/ClusterCockpit/cc-lib/v2/ccLogger"
 	"github.com/ClusterCockpit/cc-lib/v2/schema"
 	sq "github.com/Masterminds/squirrel"
+	"golang.org/x/sync/errgroup"
 )
 
 // groupBy2column maps GraphQL Aggregate enum values to their corresponding database column names.
@@ -640,30 +641,45 @@ func (r *JobRepository) AddHistograms(
 		targetBinSize = 3600
 	}
 
-	var err error
-	// Return X-Values always as seconds, will be formatted into minutes and hours in frontend
+	// Run all 4 histogram queries in parallel — each writes a distinct struct field.
+	g, gctx := errgroup.WithContext(ctx)
+
 	value := fmt.Sprintf(`CAST(ROUND(((CASE WHEN job.job_state = 'running' THEN %d - job.start_time ELSE job.duration END) / %d) + 1) as int) as value`, time.Now().Unix(), targetBinSize)
-	stat.HistDuration, err = r.jobsDurationStatisticsHistogram(ctx, value, filter, targetBinSize, &targetBinCount)
-	if err != nil {
-		cclog.Warn("Error while loading job statistics histogram: job duration")
-		return nil, err
-	}
 
-	stat.HistNumNodes, err = r.jobsStatisticsHistogram(ctx, "job.num_nodes as value", filter)
-	if err != nil {
-		cclog.Warn("Error while loading job statistics histogram: num nodes")
-		return nil, err
-	}
+	g.Go(func() error {
+		var err error
+		stat.HistDuration, err = r.jobsDurationStatisticsHistogram(gctx, value, filter, targetBinSize, &targetBinCount)
+		if err != nil {
+			cclog.Warn("Error while loading job statistics histogram: job duration")
+		}
+		return err
+	})
+	g.Go(func() error {
+		var err error
+		stat.HistNumNodes, err = r.jobsStatisticsHistogram(gctx, "job.num_nodes as value", filter)
+		if err != nil {
+			cclog.Warn("Error while loading job statistics histogram: num nodes")
+		}
+		return err
+	})
+	g.Go(func() error {
+		var err error
+		stat.HistNumCores, err = r.jobsStatisticsHistogram(gctx, "job.num_hwthreads as value", filter)
+		if err != nil {
+			cclog.Warn("Error while loading job statistics histogram: num hwthreads")
+		}
+		return err
+	})
+	g.Go(func() error {
+		var err error
+		stat.HistNumAccs, err = r.jobsStatisticsHistogram(gctx, "job.num_acc as value", filter)
+		if err != nil {
+			cclog.Warn("Error while loading job statistics histogram: num acc")
+		}
+		return err
+	})
 
-	stat.HistNumCores, err = r.jobsStatisticsHistogram(ctx, "job.num_hwthreads as value", filter)
-	if err != nil {
-		cclog.Warn("Error while loading job statistics histogram: num hwthreads")
-		return nil, err
-	}
-
-	stat.HistNumAccs, err = r.jobsStatisticsHistogram(ctx, "job.num_acc as value", filter)
-	if err != nil {
-		cclog.Warn("Error while loading job statistics histogram: num acc")
+	if err := g.Wait(); err != nil {
 		return nil, err
 	}