通过减少执行查询时需要检索的元组（tuple）的数量，以及减少查询所需的计算，函数索引能够显著改善性能。

They improve performance by reducing the number of tuples fetched during query execution.

youdao

通过减少执行查询时需要检索的元组（tuple）的数量，以及减少查询所需的计算，函数索引能够显著改善性能。

They improve performance by reducing the number of tuples fetched during query execution.

youdao