if err := DB.AutoMigrate(new(Level1), new(Level2)); err != nil {
		t.Error(err)
	}

	lvl := Level1{
		Name: "l1",
		Level2s: []Level2{
			{Name: "l2-1"}, {Name: "l2-2"},
		},
	}
	DB.Save(&lvl)

	var called int64
	DB.Callback().Query().After("gorm:query").Register("TestPreloadManyToManyCallbacks", func(_ *gorm.DB) {
		atomic.AddInt64(&called, 1)
	})

	// should therefore be always resident in the L1 cache - until we
	// have completed the construction of the result.
	// This yields significant speedups (up to +100%) in cases where
	// the result length is large (roughly, over L2 cache size).
	const chunkLimit = 8 * 1024
	chunkMax := n
	if chunkMax > chunkLimit {
		chunkMax = chunkLimit / len(b) * len(b)
		if chunkMax == 0 {
			chunkMax = len(b)
		}
	}