在此优化中，计算一次公共子表达式的值。

In this optimization, the value of a common subexpression is calculated once.

youdao

一个例子就是被下推的查询是一个公共子表达式。

One such example is when the pushed down query is a common sub-expression.

youdao

一个例子就是被下推的查询是一个公共子表达式。

One such example is when the pushed down query is a common sub-expression.

youdao