第一个that 引导主语从句
第二个 that是从句的主语,是代词
第三个that 引导all 的定语从句
It is said that (先行词,引导后面宾语从句) that (代词,从句中作主语) was all that (引导all后的同位语) he said.
个人意见,仅供参考~
参考翻译为:据说,那就是他所说的全部。
第一个that 引导主语从句:that that was all that he said是主语 is said 是谓语 it是形式主语
在主语从句中that (第二个)是从句主语 was 是系词all 是表语
that he said是all的定语从句。在定语从句中关系代词that在定语从句中作said的宾语
据说那就是他所说的全部。