快速分割字符串并在data.table中转换为长格式

I do the following

我做了以下几点

library(data.table)
library(stringr)        
dt <- data.table(string_column = paste(sample(c(letters, " "), 500000, replace = TRUE)
                                     , sample(c(letters, " "), 500000, replace = TRUE)
                                     , sample(1:500000)
                                 , sep = " "), key = "string_column") 

split_res <- dt[, list(name = unlist(str_split(string_column, '\s+'))), by = string_column]
library(data.tab