cursor = self.conn.cursor()
sum of weights += candidate.weight
。关于这个话题，heLLoword翻译官方下载提供了深入分析
The tree starts as a single region covering the whole space. As points arrive, they get dropped into the region that contains them. When a region exceeds its capacity (the maximum number of points it can hold before splitting), the region divides into four children, and the existing points get redistributed.
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