Drop GIN index on prow_jobs.variants

All variant filtering now resolves through the variant_combinations
table via variant_combination_id, making the GIN index on the
variants TEXT[] column unused. Dropping it eliminates write overhead
on prow_jobs inserts and updates.

TestOutputs and TestDurations queries updated to use
variant_combination_id IN (subquery) instead of array containment.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mstaeble

pkg/api/test_analysis.go

@@ -56,11 +56,11 @@ func GetTestAnalysisOverallFromDB(dbc *db.DB, filters *filter.Filter, release, t
 	}
 
 	for _, bv := range blockedVariants {
-		jq = jq.Where("? != ANY(prow_jobs.variants)", bv)
+		jq = jq.Where("prow_jobs.variant_combination_id NOT IN (SELECT id FROM variant_combinations WHERE ? = any(variants))", bv)
 	}
 
 	for _, av := range allowedVariants {
-		jq = jq.Where("? = ANY(prow_jobs.variants)", av)
+		jq = jq.Where("prow_jobs.variant_combination_id IN (SELECT id FROM variant_combinations WHERE ? = any(variants))", av)
 	}
 
 	r := jq.Scan(&rows)
@@ -122,11 +122,11 @@ func GetTestAnalysisByJobFromDB(dbc *db.DB, filters *filter.Filter, release, tes
 	}
 
 	for _, bv := range blockedVariants {
-		jq = jq.Where("? != ANY(variants)", bv)
+		jq = jq.Where("prow_jobs.variant_combination_id NOT IN (SELECT id FROM variant_combinations WHERE ? = any(variants))", bv)
 	}
 
 	for _, av := range allowedVariants {
-		jq = jq.Where("? = ANY(variants)", av)
+		jq = jq.Where("prow_jobs.variant_combination_id IN (SELECT id FROM variant_combinations WHERE ? = any(variants))", av)
 	}
 
 	r := jq.Scan(&rows)

pkg/db/db.go

@@ -167,7 +167,6 @@ func (d *DB) UpdateSchema(reportEnd *time.Time) error {
 		&models.ChatConversation{},
 		&jobrunscan.Label{},
 		&jobrunscan.Symptom{},
-		&models.TestDailySummary{},
 	}
 
 	// Currently we need RunMigrations to run prior
@@ -575,9 +574,15 @@ func ensureVariantCombinationTrigger(db *gorm.DB) error {
 			  AND prow_jobs.variants IS NOT NULL
 			  AND prow_jobs.variant_combination_id IS NULL;
 
-			-- Truncate test_daily_summaries if any rows lack variant_combination_id
-			-- so the next refresh repopulates with it set.
-			IF EXISTS (
+			-- Add variant_combination_id to test_daily_summaries if missing,
+			-- and truncate so the next refresh repopulates with it set.
+			IF NOT EXISTS (
+				SELECT 1 FROM information_schema.columns
+				WHERE table_name = 'test_daily_summaries' AND column_name = 'variant_combination_id'
+			) THEN
+				ALTER TABLE test_daily_summaries ADD COLUMN variant_combination_id BIGINT;
+				TRUNCATE test_daily_summaries;
+			ELSIF EXISTS (
 				SELECT 1 FROM test_daily_summaries WHERE variant_combination_id IS NULL LIMIT 1
 			) THEN
 				TRUNCATE test_daily_summaries;

pkg/db/migrations/000004_drop_variants_gin_index.down.sql

@@ -0,0 +1 @@
+CREATE INDEX IF NOT EXISTS idx_prow_jobs_variants ON prow_jobs USING gin (variants);

pkg/db/migrations/000004_drop_variants_gin_index.up.sql

@@ -0,0 +1,4 @@
+-- Drop the GIN index on prow_jobs.variants. All variant filtering now
+-- goes through variant_combination_id lookups against the small
+-- variant_combinations table, so the GIN index is unused.
+DROP INDEX IF EXISTS idx_prow_jobs_variants;

pkg/db/models/prow.go

@@ -25,7 +25,7 @@ type ProwJob struct {
 	Kind     ProwKind
 	Name     string         `gorm:"unique"`
 	Release  string         `gorm:"index"`
-	Variants pq.StringArray `gorm:"type:text[];index:idx_prow_jobs_variants,type:gin"`
+	Variants pq.StringArray `gorm:"type:text[]"`
 	// VariantCombinationID references variant_combinations.id, maintained by a
 	// BEFORE INSERT/UPDATE trigger. NULL only when Variants is NULL.
 	VariantCombinationID *uint `gorm:"column:variant_combination_id"`

pkg/db/query/test_queries.go

@@ -268,11 +268,11 @@ func TestOutputs(dbc *db.DB, release, test string, includedVariants, excludedVar
 		Where("prow_job_run_test_outputs.prow_job_run_test_release = ?", release)
 
 	for _, variant := range includedVariants {
-		q = q.Where("? = any(prow_jobs.variants)", variant)
+		q = q.Where("prow_jobs.variant_combination_id IN (SELECT id FROM variant_combinations WHERE ? = any(variants))", variant)
 	}
 
 	for _, variant := range excludedVariants {
-		q = q.Where("NOT ? = any(prow_jobs.variants)", variant)
+		q = q.Where("prow_jobs.variant_combination_id NOT IN (SELECT id FROM variant_combinations WHERE ? = any(variants))", variant)
 	}
 
 	res := q.
@@ -301,11 +301,11 @@ func TestDurations(dbc *db.DB, release, test string, includedVariants, excludedV
 		Where("prow_job_run_tests.prow_job_run_release = ?", release)
 
 	for _, variant := range includedVariants {
-		q = q.Where("? = any(prow_jobs.variants)", variant)
+		q = q.Where("prow_jobs.variant_combination_id IN (SELECT id FROM variant_combinations WHERE ? = any(variants))", variant)
 	}
 
 	for _, variant := range excludedVariants {
-		q = q.Where("NOT ? = any(prow_jobs.variants)", variant)
+		q = q.Where("prow_jobs.variant_combination_id NOT IN (SELECT id FROM variant_combinations WHERE ? = any(variants))", variant)
 	}
 
 	res := q.