[Feature Request] el-table summary-method method was called too many times

[AlexStacker]

Existing Component

是

Component Name

el-table

Description

table-footer.jsL57-L67行，每次循环一个columns时都会调用一次summary-method，而这个方法第一次返回的值是个数组，已经确定了，不需要每次调用，每次调用会在数据量大的时候导致速度很慢。

[element-bot]

Translation of this issue:

Existing Component
yes

Component Name
El-table

Description
table-footer.jsL57-L67 line, summary-method is called once every time a columns is circulate, and the first return value of this method is an array, which has been determined, and does not need to call the same result every time, resulting in a slow speed when the amount of data is large.