选择率,基数计算公式
单个谓词过滤：
= 基数计算公式 ：1/num_distinct*(num_rows-num_nulls),如果有直方图，基数计算公式=(num_rows-num_nulls)*density
> 基数计算公式：(high_value-limit)/(high_value-low_value)*(num_rows-num_nulls)
>=基数计算公式：((high_value-limit)/(high_value-low_value)+1/num_distinct)*(num_rows-num_nulls) 因为有=，所以要加上=的选择率，=的选择率为1/num_distinct
< 基数计算公式：(limit-low_value)/(high_value-low_value)*(num_rows-num_nulls)
<=基数计算公式：((limit-low_value)/(high_value-low_value)+1/num_distinct)*(num_rows-num_nulls)
between ... and .... 的基数计算公式等价于 xxx<= high_limit ,xxxx>=low_limit
基数计算公式：((high_limit-low_limit)/(high_value-low_value)+2/num_distinct)*(num_rows-num_nulls)
low_limit< and < high_limit 基数计算公式：(high_limit-low_limit)/(high_value-low_value)*(num_rows-num_nulls)
low_limit<= and <high_limit 基数计算公式：(high_limit-low_limit)/(high_value-low_value)+1/num_distinct)*(num_rows-num_nulls)
双谓词，多谓词
A AND B 选择率计算公式=A选择率*B选择率
A OR B 选择率计算公式=A+B-A AND B
NOT A 选择率计算公式= 1- A选择率
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