Manages the cache

Manages whether cdo will try to recover existing files if available.

Usage

cdo_cache_set(cache = tempdir())

cdo_cache_get()

cdo_cache_unset()

Arguments

cache

either the location of the default cache or a list which is the result of a previous cdo_cache_set() call.

Value

A list with the old values of the rcdo_cache and rcdo_tmpdir options.

Details

When first executing the operation, cdo_execute() will create a ".hash" file matching the output file name with a hash generated from the current cdo version, the text of the command, the sum of the file sizes of the input files and the most recent modified time of the input files. The next time the same command is executed, if the cache is active, cdo_execute will compute the same hash and compare it with the file and, if it matches, it will return the output file without running the command. Caching currently only works with operations with only one output file.

These functions change the global options. If used inside functions, it's generally a good idea to reset the original values before exiting the function with on.exit().

Examples

# Set the cache
old <- cdo_cache_set(cache = "data/cache")

# Reset the cache to its previous state
cdo_cache_set(old)

# Disable the cache
old <- cdo_cache_unset()

# Again, reset the cache to its previous state.
cdo_cache_set(old)

with_cache <- function(operation, cache) {
  old <- cdo_cache_set(cache)
  on.exit(cdo_cache_set(old))

  # Rest of the function
}

without_cache <- function(operation) {
  old <- cdo_cache_unset(cache)
  on.exit(cdo_cache_set(old))

  # Rest of the function
}