Align DeliveryResult tags and make the index table test-local

Re-align the json tag column in DeliveryResult after the wider
DeliveryID gorm tag, and move the test's index table out of package
scope into the test function.

Model: opus-5-5

README.md

@@ -1760,6 +1760,22 @@ retries) is individually logged for full observability.
 
 **Relations:** Belongs to Delivery.
 
+#### Event-tier indexes
+
+Beyond the primary keys, the per-webhook event databases carry secondary
+indexes on the columns the background work reads by, each created by
+`AutoMigrate` on a fresh and on an existing database:
+
+| Column                         | Serves |
+| ------------------------------ | ------ |
+| `deliveries.status`            | The recovery and sweep queries that select deliveries by status once a minute |
+| `deliveries.event_id`          | Loading a page of the event log, which reads deliveries by event |
+| `delivery_results.delivery_id` | Loading a page of the event log, which reads results by delivery |
+| `events.created_at`            | Retention, which deletes events by age |
+
+The `events.resubmitted_from_id` column is also indexed, to resolve the
+resubmit relationship both ways in the event log.
+
 #### Common Fields
 
 Every entity except `Setting` includes these fields from `BaseModel`.

internal/database/event_tier_indexes_test.go

@@ -0,0 +1,72 @@
+package database_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// indexedColumn names a secondary index by the model and struct field
+// GORM derives the index name from.
+type indexedColumn struct {
+	model any
+	field string
+}
+
+// TestWebhookDBManager_OpenAddsEventTierIndexes verifies that opening a
+// per-webhook database that predates these indexes creates them, so the
+// queries that read by those columns stop scanning whole tables. It
+// stands in for an older database file by dropping the indexes
+// AutoMigrate just created, then reopening the same file.
+func TestWebhookDBManager_OpenAddsEventTierIndexes(t *testing.T) {
+	t.Parallel()
+
+	// The columns the background work reads by: the recovery and sweep
+	// queries (status), the event log (event_id and delivery_id) and
+	// retention (created_at).
+	eventTierIndexes := []indexedColumn{
+		{&database.Delivery{}, "Status"},
+		{&database.Delivery{}, "EventID"},
+		{&database.DeliveryResult{}, "DeliveryID"},
+		{&database.Event{}, "CreatedAt"},
+	}
+
+	mgr, lc := setupTestWebhookDBManager(t)
+	ctx := context.Background()
+	require.NoError(t, lc.Start(ctx))
+
+	defer func() { require.NoError(t, lc.Stop(ctx)) }()
+
+	webhookID := uuid.New().String()
+
+	db, err := mgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	// A fresh database has them.
+	for _, ix := range eventTierIndexes {
+		require.True(t, db.Migrator().HasIndex(ix.model, ix.field))
+	}
+
+	// Stand in for a database file created before the indexes existed.
+	for _, ix := range eventTierIndexes {
+		require.NoError(t, db.Migrator().DropIndex(ix.model, ix.field))
+		require.False(t, db.Migrator().HasIndex(ix.model, ix.field))
+	}
+
+	// Drop the cached connection so the next open reopens the file and
+	// runs AutoMigrate against it, as a restart would.
+	require.NoError(t, mgr.CloseAll())
+
+	db, err = mgr.GetDB(webhookID)
+	require.NoError(t, err)
+
+	for _, ix := range eventTierIndexes {
+		assert.True(t, db.Migrator().HasIndex(ix.model, ix.field),
+			"opening the existing database should create the index on %s",
+			ix.field)
+	}
+}

internal/database/model_delivery.go

@@ -32,9 +32,9 @@ func (s DeliveryStatus) Terminal() bool {
 type Delivery struct {
 	BaseModel
 
-	EventID  string         `gorm:"type:uuid;not null"         json:"eventId"`
+	EventID  string         `gorm:"type:uuid;not null;index"         json:"eventId"`
 	TargetID string         `gorm:"type:uuid;not null"               json:"targetId"`
-	Status   DeliveryStatus `gorm:"not null;default:'pending'" json:"status"`
+	Status   DeliveryStatus `gorm:"not null;default:'pending';index" json:"status"`
 
 	// Relations
 	Event           Event            `json:"event,omitzero"`

internal/database/model_delivery_result.go

@@ -4,7 +4,7 @@ package database
 type DeliveryResult struct {
 	BaseModel
 
-	DeliveryID   string `gorm:"type:uuid;not null"   json:"deliveryId"`
+	DeliveryID   string `gorm:"type:uuid;not null;index" json:"deliveryId"`
 	AttemptNum   int    `gorm:"not null"                 json:"attemptNum"`
 	Success      bool   `json:"success"`
 	StatusCode   int    `json:"statusCode,omitempty"`

internal/database/model_event.go

@@ -1,9 +1,17 @@
 package database
 
+import "time"
+
 // Event represents a captured webhook event
 type Event struct {
 	BaseModel
 
+	// CreatedAt overrides BaseModel.CreatedAt only to add an index:
+	// retention deletes events by age, so events.created_at is queried
+	// on every sweep. The other tables keep the unindexed BaseModel
+	// field.
+	CreatedAt time.Time `gorm:"index" json:"createdAt"`
+
 	WebhookID    string `gorm:"type:uuid;not null" json:"webhookId"`
 	EntrypointID string `gorm:"type:uuid;not null" json:"entrypointId"`