code: func reCalcCapacity(c *Chunk, maxChunkSize int) int {
  	if c.NumRows() < c.capacity {
  		return c.capacity
  	}
  	return mathutil.Min(c.capacity*2, maxChunkSize)
  }
docs: // reCalcCapacity calculates the capacity for another Chunk based on the current
  // Chunk. The new capacity is doubled only when the current Chunk is full.