feature suggestion: option to save stashed objects to memory

[vorpalvorpal]

I have a large dataframe that is built by doing computationally expensive joins of other dataframes. I have a function that returns this dataframe that looks like this:

data_df <- function(options){
    df <-  
       mustashe::stash(
      "stash_dataDF", 
      {df <- data.frame() # lots of expensive joins here}, 
      depends_on = c(getOption("DFs")),
      functional = TRUE) 
    if (missing(options)) return(df)
   else {
       # do some post-processing of df based on options
       return(df)
    }
}

When I run this and it looks up stash_dataDF and finds that it can load the stashed object, it then has to load stash_dataDF.qs from disk. In my case, this tends to take between 0.25 - 0.5 seconds. Which isn't much, but does add up if data_df() is called multiple times within a larger workflow. I wonder if it would be possible to add an option to save stash_dataDF as an in-memory object and then use the same hash checking as is currently done. stash_dataDF would still need to either be built fresh or loaded from stash_dataDF.qs at the beginning of each session, but then after that, this should be a lot faster than reading it from disk each time.

[jhrcook]

This is an interesting idea, I just don't have the time to implement it. A pull request is welcome though!

[DarwinAwardWinner]

As an alternative, you could consider implementing support for cachem, which supports both disk and memory-backed key-value stores, plus additional features such as pruning of old values.