feat: add hot path indexes for watch list and cache queries

internal/database/database_test.go

@@ -0,0 +1,40 @@
+package database
+
+import (
+	"database/sql"
+	"testing"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+func TestRunMigrationsCreatesHotPathIndexes(t *testing.T) {
+	sqlDB, err := sql.Open("sqlite3", ":memory:")
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	defer sqlDB.Close()
+	sqlDB.SetMaxOpenConns(1)
+
+	if err := RunMigrations(sqlDB); err != nil {
+		t.Fatalf("RunMigrations: %v", err)
+	}
+
+	for _, indexName := range []string{
+		"idx_watch_list_entry_user_updated_at",
+		"idx_watch_list_entry_user_status_updated_at_desc",
+		"idx_watch_list_entry_status_updated_at_anime_id",
+		"idx_continue_watching_anime_id",
+		"idx_jikan_cache_expires_at_datetime",
+	} {
+		t.Run(indexName, func(t *testing.T) {
+			var count int
+			err := sqlDB.QueryRow(`SELECT COUNT(*) FROM sqlite_master WHERE type = 'index' AND name = ?`, indexName).Scan(&count)
+			if err != nil {
+				t.Fatalf("query index: %v", err)
+			}
+			if count != 1 {
+				t.Fatalf("index %s count = %d, want 1", indexName, count)
+			}
+		})
+	}
+}