drake_cache: Get the cache of a `drake` project.

Description

make() saves the values of your targets so you rarely need to think about output files. By default, the cache is a hidden folder called .drake/. You can also supply your own storr cache to the cache argument of make(). The drake_cache() function retrieves this cache.

Usage

drake_cache(path = NULL, verbose = NULL, console_log_file = NULL)

Value

A drake/storr cache in a folder called .drake/, if available. NULL otherwise.

Arguments

path: Character. Set path to the path of a storr::storr_rds() cache to retrieve a specific cache generated by storr::storr_rds() or drake::new_cache(). If the path argument is NULL, drake_cache() searches up through parent directories to find a folder called .drake/.
verbose: Deprecated on 2019-09-11.
console_log_file: Deprecated on 2019-09-11.

Details

drake_cache() actually returns a decorated storr, an object that contains a storr (plus bells and whistles). To get the actual inner storr, use drake_cache()$storr. Most methods are delegated to the inner storr. Some methods and objects are new or overwritten. Here are the ones relevant to users.

history: drake's history (which powers drake_history()) is a txtq. Access it with drake_cache()$history.
import(): The import() method is a function that can import targets, function dependencies, etc. from one decorated storr to another. History is not imported. For that, you have to work with the history txtqs themselves, Arguments to import():
- ... and list: specify targets to import just like with loadd(). Leave these blank to import everything.
- from: the decorated storr from which to import targets.
- jobs: number of local processes for parallel computing.
- gc: TRUE or FALSE, whether to run garbage collection for memory after importing each target. Recommended, but slow.
export(): Same as import(), except the from argument is replaced by to: the decorated storr where the targets end up.

Examples

Run this code

if (FALSE) {
isolate_example("Quarantine side effects.", {
if (suppressWarnings(require("knitr"))) {
clean(destroy = TRUE)
# No cache is available.
drake_cache() # NULL
load_mtcars_example() # Get the code with drake_example("mtcars").
make(my_plan) # Run the project, build the targets.
x <- drake_cache() # Now, there is a cache.
y <- storr::storr_rds(".drake") # Nearly equivalent.
# List the objects readable from the cache with readd().
x$list()
# drake_cache() actually returns a *decorated* storr.
# The *real* storr is inside.
drake_cache()$storr
}
# You can import and export targets to and from decorated storrs.
plan1 <- drake_plan(w = "w", x = "x")
plan2 <- drake_plan(a = "a", x = "x2")
cache1 <- new_cache("cache1")
cache2 <- new_cache("cache2")
make(plan1, cache = cache1)
make(plan2, cache = cache2)
cache1$import(cache2, a)
cache1$get("a")
cache1$get("x")
cache1$import(cache2)
cache1$get("x")
# With txtq >= 0.1.6.9002, you can import history from one cache into
# another.
# nolint start
# drake_history(cache = cache1)
# cache1$history$import(cache2$history)
# drake_history(cache = cache1)
# nolint end
})
}