关系矩阵 一个可以从非常大的关系数据中快速计算唯一实体的库。 例如) SELECT domain, relation FROM relations; |domain |relation |-------|------- |0 |1 |0 |4 |1 |2 |2 |3 |2 |4 |2 |5 ... SELECT DISTINCT relation FROM relations WHERE domain IN (0, 2, ...) |relation |------- |1 |3 |4 |5 ... 可以这样计算: val ma