# Introduction to Cache

#### Eliot J. B. McIntire

#### August 25 2026

# 1 Reproducible workflow

As part of a reproducible workflow, caching of function calls, code chunks, and other elements of a project is a critical component. The objective of a reproducible workflow is is likely that an entire work flow from raw data to publication, decision support, report writing, presentation building etc., could be built and be reproducible anywhere, on any computer, operating system, with any starting conditions, on demand. The `reproducible::Cache` function is built to work with any R function.

## 1.1 Differences with other approaches

`Cache` users `DBI` as a backend, with key functions, `dbReadTable`, `dbRemoveTable`, `dbSendQuery`, `dbSendStatement`, `dbCreateTable` and `dbAppendTable`. These can all be accessed via `Cache`, `showCache`, `clearCache`, and `keepCache`. It is optimized for speed of transactions, using `digest::digest` on objects and files. The main function is superficially similar to `archivist::cache`, which uses `digest::digest` in all cases to determine whether the arguments are identical in subsequent iterations. It also but does many things that make standard caching with `digest::digest` don’t work reliably between systems. For these, the function `.robustDigest` is introduced to make caching transferable between systems. This is relevant for file paths, environments, parallel clusters, functions (which are contained within an environment), and many others (e.g., see `?.robustDigest` for methods). `Cache` also adds important elements like automated tagging and the option to retrieve disk-cached values via stashed objects in memory using `memoise::memoise`. This means that running `Cache` 1, 2, and 3 times on the same function will get progressively faster. This can be extremely useful for web apps built with, say `shiny`.

## 1.2 Function-level caching

Any function can be cached by wrapping `Cache` around the function call, or by using base pipe `|>`:

This will be a slight change to a function call, such as: `terra::project(raster, crs = terra::crs(newRaster))` to `Cache(terra::project(raster, crs = terra::crs(newRaster)))` or with the pipe, which may be more convenient as it is easy to add and remove caching in the code base: `terra::project(raster, crs = terra::crs(newRaster)) |> Cache()`

This is particularly useful for expensive operations.

    library(reproducible)
    library(data.table)

    ##
    ## Attaching package: 'data.table'

    ## The following object is masked from 'package:terra':
    ##
    ##     shift

    tmpDir <- file.path(tempfile(), "reproducible_examples", "Cache")
    dir.create(tmpDir, recursive = TRUE)

    # Source raster with a complete LCC definition
    ras <- terra::rast(terra::ext(0, 300, 0, 300), vals = 1:9e4, res = 1)
    terra::crs(ras) <- "+proj=lcc +lat_1=60 +lat_2=70 +lat_0=50 +lon_0=-100 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs"

    # Target CRS in PROJ form (no EPSG lookup)
    newCRS <- "+proj=longlat +datum=WGS84 +no_defs"

    # Derive target extent from source extent (no registry lookup)
    target_ext <- terra::project(terra::ext(ras), from = terra::crs(ras), to = newCRS)

    # Build template with chosen resolution; assign CRS
    tmplate <- terra::rast(target_ext, resolution = 0.00001)
    terra::crs(tmplate) <- newCRS

    # No Cache
    system.time(map1 <- terra::project(ras, tmplate, method = "near"))

    ##    user  system elapsed
    ##   0.026   0.002   0.028

    # Try with memoise for this example -- for many simple cases, memoising will not be faster
    opts <- options("reproducible.useMemoise" = TRUE)
    # With Cache -- a little slower the first time because saving to disk
    system.time({
      suppressWarnings({
        map1 <- terra::project(ras, tmplate, method = "near") |>
          Cache(cachePath = tmpDir)
      })
    })

    ## Saved! Cache file: b080b61ea3444bd7.rds; fn: project (and added a memoised copy)

    ##    user  system elapsed
    ##   0.415   0.015   0.437

    # faster the second time; improvement depends on size of object and time to run function
    system.time({
      map2 <- terra::project(ras, tmplate, method = "near") |>
        Cache(cachePath = tmpDir)
    })

    ## Object to retrieve (fn: project, b080b61ea3444bd7.rds) ...

    ## Loaded! Memoised result from previous project call

    ##    user  system elapsed
    ##   0.038   0.000   0.039

    options(opts)

    all.equal(map1, map2, check.attributes = FALSE) # TRUE

    ## [1] "Attributes: < Component \".Cache\": Component \"newCache\": 1 element mismatch >"

## 1.3 Caching examples

### 1.3.1 Basic use

    try(clearCache(tmpDir, ask = FALSE), silent = TRUE) # just to make sure it is clear

    ranNumsA <- rnorm(10, 16) |> Cache(cachePath = tmpDir)

    ## Saved! Cache file: aa549dd751b2f26d.rds; fn: rnorm

    # All same
    ranNumsB <- rnorm(10, 16) |> Cache(cachePath = tmpDir) # recovers cached copy

    ## Object to retrieve (fn: rnorm, aa549dd751b2f26d.rds) ...

    ## Loaded! Cached result from previous rnorm call

    ranNumsD1 <- Cache(quote(rnorm(n = 10, 16))) |> Cache(cachePath = tmpDir) # recovers cached copy

    ## No cachePath supplied. Using /tmp/Rtmpxynttl/reproducible/cache

    ## Saved! Cache file: aa549dd751b2f26d.rds; fn: rnorm

    ## Saved! Cache file: e1a8736c014448e0.rds; fn: Cache

    ranNumsD2 <- Cache(rnorm(n = 10, 16)) |> Cache(cachePath = tmpDir) # recovers cached copy

    ## No cachePath supplied and getOption('reproducible.cachePath') is inside a temporary directory;
    ##   this will not persist across R sessions.

    ## Object to retrieve (fn: rnorm, aa549dd751b2f26d.rds) ...

    ## Loaded! Cached result from previous rnorm call

    ## Saved! Cache file: 50d742627d1da044.rds; fn: Cache

    # pipe
    ranNumsD3 <- rnorm(n = 10, 16) |> Cache(cachePath = tmpDir) # recovers cached copy

    ## Object to retrieve (fn: rnorm, aa549dd751b2f26d.rds) ...

    ## Loaded! Cached result from previous rnorm call

    # Any minor change makes it different
    ranNumsE <- rnorm(10, 6) |> Cache(cachePath = tmpDir) # different

    ## Saved! Cache file: d78b46a2a76d6d80.rds; fn: rnorm

#### 1.3.1.1 Example 1: Basic cache use with tags

    ranNumsA <- rnorm(4) |> Cache(cachePath = tmpDir, userTags = "objectName:a")

    ## Saved! Cache file: adf21923cd1e50d0.rds; fn: rnorm

    ranNumsB <- runif(4) |> Cache(cachePath = tmpDir, userTags = "objectName:b")

    ## Saved! Cache file: e23cab430872a0ea.rds; fn: runif

    showCache(tmpDir, userTags = c("objectName"))

    ## Cache size:

    ## Total (including Rasters): 40 bytes

    ## Selected objects (not including Rasters): 40 bytes

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: adf21923cd1e50d0            function                     rnorm
    ##  2: adf21923cd1e50d0          objectName                         a
    ##  3: adf21923cd1e50d0            accessed 2026-08-25 12:32:25.23940
    ##  4: adf21923cd1e50d0             inCloud                     FALSE
    ##  5: adf21923cd1e50d0   elapsedTimeDigest          0.004152536 secs
    ##  6: adf21923cd1e50d0           preDigest     .FUN:4f604aa46882b368
    ##  7: adf21923cd1e50d0           preDigest     mean:c40c00762a0dac94
    ##  8: adf21923cd1e50d0           preDigest        n:7eef4eae85fd9229
    ##  9: adf21923cd1e50d0           preDigest       sd:853b1797f54b229c
    ## 10: adf21923cd1e50d0               class                   numeric
    ## 11: adf21923cd1e50d0         object.size                        80
    ## 12: adf21923cd1e50d0            fromDisk                     FALSE
    ## 13: adf21923cd1e50d0          resultHash
    ## 14: adf21923cd1e50d0 elapsedTimeFirstRun          0.001330614 secs
    ## 15: e23cab430872a0ea            function                     runif
    ## 16: e23cab430872a0ea          objectName                         b
    ## 17: e23cab430872a0ea            accessed 2026-08-25 12:32:25.24496
    ## 18: e23cab430872a0ea             inCloud                     FALSE
    ## 19: e23cab430872a0ea   elapsedTimeDigest           0.00126338 secs
    ## 20: e23cab430872a0ea           preDigest     .FUN:881ec847b7161f3c
    ## 21: e23cab430872a0ea           preDigest      max:853b1797f54b229c
    ## 22: e23cab430872a0ea           preDigest      min:c40c00762a0dac94
    ## 23: e23cab430872a0ea           preDigest        n:7eef4eae85fd9229
    ## 24: e23cab430872a0ea               class                   numeric
    ## 25: e23cab430872a0ea         object.size                        80
    ## 26: e23cab430872a0ea            fromDisk                     FALSE
    ## 27: e23cab430872a0ea          resultHash
    ## 28: e23cab430872a0ea elapsedTimeFirstRun         0.0008897781 secs
    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:25.241488
    ##  2: 2026-08-25 12:32:25.241488
    ##  3: 2026-08-25 12:32:25.241488
    ##  4: 2026-08-25 12:32:25.241488
    ##  5: 2026-08-25 12:32:25.241488
    ##  6: 2026-08-25 12:32:25.241488
    ##  7: 2026-08-25 12:32:25.241488
    ##  8: 2026-08-25 12:32:25.241488
    ##  9: 2026-08-25 12:32:25.241488
    ## 10: 2026-08-25 12:32:25.241488
    ## 11: 2026-08-25 12:32:25.241488
    ## 12: 2026-08-25 12:32:25.241488
    ## 13: 2026-08-25 12:32:25.241488
    ## 14: 2026-08-25 12:32:25.241488
    ## 15: 2026-08-25 12:32:25.246666
    ## 16: 2026-08-25 12:32:25.246666
    ## 17: 2026-08-25 12:32:25.246666
    ## 18: 2026-08-25 12:32:25.246666
    ## 19: 2026-08-25 12:32:25.246666
    ## 20: 2026-08-25 12:32:25.246666
    ## 21: 2026-08-25 12:32:25.246666
    ## 22: 2026-08-25 12:32:25.246666
    ## 23: 2026-08-25 12:32:25.246666
    ## 24: 2026-08-25 12:32:25.246666
    ## 25: 2026-08-25 12:32:25.246666
    ## 26: 2026-08-25 12:32:25.246666
    ## 27: 2026-08-25 12:32:25.246666
    ## 28: 2026-08-25 12:32:25.246666
    ##                    createdDate
    ##                         <char>

    showCache(tmpDir, userTags = c("^a$")) # regular expression ... "a" exactly

    ## Cache size:

    ## Total (including Rasters): 20 bytes

    ## Selected objects (not including Rasters): 20 bytes

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: adf21923cd1e50d0            function                     rnorm
    ##  2: adf21923cd1e50d0          objectName                         a
    ##  3: adf21923cd1e50d0            accessed 2026-08-25 12:32:25.23940
    ##  4: adf21923cd1e50d0             inCloud                     FALSE
    ##  5: adf21923cd1e50d0   elapsedTimeDigest          0.004152536 secs
    ##  6: adf21923cd1e50d0           preDigest     .FUN:4f604aa46882b368
    ##  7: adf21923cd1e50d0           preDigest     mean:c40c00762a0dac94
    ##  8: adf21923cd1e50d0           preDigest        n:7eef4eae85fd9229
    ##  9: adf21923cd1e50d0           preDigest       sd:853b1797f54b229c
    ## 10: adf21923cd1e50d0               class                   numeric
    ## 11: adf21923cd1e50d0         object.size                        80
    ## 12: adf21923cd1e50d0            fromDisk                     FALSE
    ## 13: adf21923cd1e50d0          resultHash
    ## 14: adf21923cd1e50d0 elapsedTimeFirstRun          0.001330614 secs
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:25.241488
    ##  2: 2026-08-25 12:32:25.241488
    ##  3: 2026-08-25 12:32:25.241488
    ##  4: 2026-08-25 12:32:25.241488
    ##  5: 2026-08-25 12:32:25.241488
    ##  6: 2026-08-25 12:32:25.241488
    ##  7: 2026-08-25 12:32:25.241488
    ##  8: 2026-08-25 12:32:25.241488
    ##  9: 2026-08-25 12:32:25.241488
    ## 10: 2026-08-25 12:32:25.241488
    ## 11: 2026-08-25 12:32:25.241488
    ## 12: 2026-08-25 12:32:25.241488
    ## 13: 2026-08-25 12:32:25.241488
    ## 14: 2026-08-25 12:32:25.241488

    showCache(tmpDir, userTags = c("runif")) # show only cached objects made during runif call

    ## Cache size:

    ## Total (including Rasters): 20 bytes

    ## Selected objects (not including Rasters): 20 bytes

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: e23cab430872a0ea            function                     runif
    ##  2: e23cab430872a0ea          objectName                         b
    ##  3: e23cab430872a0ea            accessed 2026-08-25 12:32:25.24496
    ##  4: e23cab430872a0ea             inCloud                     FALSE
    ##  5: e23cab430872a0ea   elapsedTimeDigest           0.00126338 secs
    ##  6: e23cab430872a0ea           preDigest     .FUN:881ec847b7161f3c
    ##  7: e23cab430872a0ea           preDigest      max:853b1797f54b229c
    ##  8: e23cab430872a0ea           preDigest      min:c40c00762a0dac94
    ##  9: e23cab430872a0ea           preDigest        n:7eef4eae85fd9229
    ## 10: e23cab430872a0ea               class                   numeric
    ## 11: e23cab430872a0ea         object.size                        80
    ## 12: e23cab430872a0ea            fromDisk                     FALSE
    ## 13: e23cab430872a0ea          resultHash
    ## 14: e23cab430872a0ea elapsedTimeFirstRun         0.0008897781 secs
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:25.246666
    ##  2: 2026-08-25 12:32:25.246666
    ##  3: 2026-08-25 12:32:25.246666
    ##  4: 2026-08-25 12:32:25.246666
    ##  5: 2026-08-25 12:32:25.246666
    ##  6: 2026-08-25 12:32:25.246666
    ##  7: 2026-08-25 12:32:25.246666
    ##  8: 2026-08-25 12:32:25.246666
    ##  9: 2026-08-25 12:32:25.246666
    ## 10: 2026-08-25 12:32:25.246666
    ## 11: 2026-08-25 12:32:25.246666
    ## 12: 2026-08-25 12:32:25.246666
    ## 13: 2026-08-25 12:32:25.246666
    ## 14: 2026-08-25 12:32:25.246666

    clearCache(tmpDir, userTags = c("runif"), ask = FALSE) # remove only cached objects made during runif call

    ## Cache size:

    ## Total (including Rasters): 20 bytes

    ## Selected objects (not including Rasters): 20 bytes

    showCache(tmpDir) # all

    ## Cache size:

    ## Total (including Rasters): 482 bytes

    ## Selected objects (not including Rasters): 482 bytes

    ##              cacheId              tagKey                         tagValue
    ##               <char>              <char>                           <char>
    ##  1: 50d742627d1da044            function                            Cache
    ##  2: 50d742627d1da044            accessed        2026-08-25 12:32:25.19335
    ##  3: 50d742627d1da044             inCloud                            FALSE
    ##  4: 50d742627d1da044   elapsedTimeDigest                 0.002197742 secs
    ##  5: 50d742627d1da044           preDigest             FUN:5d16a3e3d556b981
    ##  6: 50d742627d1da044           preDigest cacheSaveFormat:cf2828ea967d53e7
    ##  7: 50d742627d1da044           preDigest          dryRun:e9aac936a0e8f6ae
    ##  8: 50d742627d1da044           preDigest            .FUN:53b64a48c1458486
    ##  9: 50d742627d1da044           preDigest  .cacheChaining:71681d621365dfd7
    ## 10: 50d742627d1da044           preDigest     .cacheExtra:c85d88fc56f4e042
    ## 11: 50d742627d1da044           preDigest   .functionName:c85d88fc56f4e042
    ## 12: 50d742627d1da044           preDigest            conn:118387d5d48f757d
    ## 13: 50d742627d1da044           preDigest             drv:9ce9a83896bf68a1
    ## 14: 50d742627d1da044               class                          numeric
    ## 15: 50d742627d1da044         object.size                              176
    ## 16: 50d742627d1da044            fromDisk                            FALSE
    ## 17: 50d742627d1da044          resultHash
    ## 18: 50d742627d1da044 elapsedTimeFirstRun                 0.006744623 secs
    ## 19: aa549dd751b2f26d            function                            rnorm
    ## 20: aa549dd751b2f26d            accessed        2026-08-25 12:32:25.16793
    ## 21: aa549dd751b2f26d             inCloud                            FALSE
    ## 22: aa549dd751b2f26d   elapsedTimeDigest                 0.001362562 secs
    ## 23: aa549dd751b2f26d           preDigest            .FUN:4f604aa46882b368
    ## 24: aa549dd751b2f26d           preDigest            mean:15620f138033a66c
    ## 25: aa549dd751b2f26d           preDigest               n:c5775c3b366fb719
    ## 26: aa549dd751b2f26d           preDigest              sd:853b1797f54b229c
    ## 27: aa549dd751b2f26d               class                          numeric
    ## 28: aa549dd751b2f26d         object.size                              176
    ## 29: aa549dd751b2f26d            fromDisk                            FALSE
    ## 30: aa549dd751b2f26d          resultHash
    ## 31: aa549dd751b2f26d elapsedTimeFirstRun                 0.001132011 secs
    ## 32: aa549dd751b2f26d            accessed        2026-08-25 12:32:25.17573
    ## 33: aa549dd751b2f26d            accessed        2026-08-25 12:32:25.20629
    ## 34: adf21923cd1e50d0            function                            rnorm
    ## 35: adf21923cd1e50d0          objectName                                a
    ## 36: adf21923cd1e50d0            accessed        2026-08-25 12:32:25.23940
    ## 37: adf21923cd1e50d0             inCloud                            FALSE
    ## 38: adf21923cd1e50d0   elapsedTimeDigest                 0.004152536 secs
    ## 39: adf21923cd1e50d0           preDigest            .FUN:4f604aa46882b368
    ## 40: adf21923cd1e50d0           preDigest            mean:c40c00762a0dac94
    ## 41: adf21923cd1e50d0           preDigest               n:7eef4eae85fd9229
    ## 42: adf21923cd1e50d0           preDigest              sd:853b1797f54b229c
    ## 43: adf21923cd1e50d0               class                          numeric
    ## 44: adf21923cd1e50d0         object.size                               80
    ## 45: adf21923cd1e50d0            fromDisk                            FALSE
    ## 46: adf21923cd1e50d0          resultHash
    ## 47: adf21923cd1e50d0 elapsedTimeFirstRun                 0.001330614 secs
    ## 48: d78b46a2a76d6d80            function                            rnorm
    ## 49: d78b46a2a76d6d80            accessed        2026-08-25 12:32:25.20977
    ## 50: d78b46a2a76d6d80             inCloud                            FALSE
    ## 51: d78b46a2a76d6d80   elapsedTimeDigest                  0.00126791 secs
    ## 52: d78b46a2a76d6d80           preDigest            .FUN:4f604aa46882b368
    ## 53: d78b46a2a76d6d80           preDigest            mean:152602b8ff81e5bb
    ## 54: d78b46a2a76d6d80           preDigest               n:c5775c3b366fb719
    ## 55: d78b46a2a76d6d80           preDigest              sd:853b1797f54b229c
    ## 56: d78b46a2a76d6d80               class                          numeric
    ## 57: d78b46a2a76d6d80         object.size                              176
    ## 58: d78b46a2a76d6d80            fromDisk                            FALSE
    ## 59: d78b46a2a76d6d80          resultHash
    ## 60: d78b46a2a76d6d80 elapsedTimeFirstRun                0.0008654594 secs
    ## 61: e1a8736c014448e0            function                            Cache
    ## 62: e1a8736c014448e0            accessed        2026-08-25 12:32:25.18054
    ## 63: e1a8736c014448e0             inCloud                            FALSE
    ## 64: e1a8736c014448e0   elapsedTimeDigest                 0.002479553 secs
    ## 65: e1a8736c014448e0           preDigest             FUN:265d86c3bd130de5
    ## 66: e1a8736c014448e0           preDigest cacheSaveFormat:cf2828ea967d53e7
    ## 67: e1a8736c014448e0           preDigest          dryRun:e9aac936a0e8f6ae
    ## 68: e1a8736c014448e0           preDigest            .FUN:53b64a48c1458486
    ## 69: e1a8736c014448e0           preDigest  .cacheChaining:71681d621365dfd7
    ## 70: e1a8736c014448e0           preDigest     .cacheExtra:c85d88fc56f4e042
    ## 71: e1a8736c014448e0           preDigest   .functionName:c85d88fc56f4e042
    ## 72: e1a8736c014448e0           preDigest            conn:118387d5d48f757d
    ## 73: e1a8736c014448e0           preDigest             drv:9ce9a83896bf68a1
    ## 74: e1a8736c014448e0               class                             call
    ## 75: e1a8736c014448e0         object.size                             1320
    ## 76: e1a8736c014448e0            fromDisk                            FALSE
    ## 77: e1a8736c014448e0          resultHash
    ## 78: e1a8736c014448e0 elapsedTimeFirstRun                 0.007514238 secs
    ##              cacheId              tagKey                         tagValue
    ##               <char>              <char>                           <char>
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:25.201069
    ##  2: 2026-08-25 12:32:25.201069
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    ##  4: 2026-08-25 12:32:25.201069
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    ## 10: 2026-08-25 12:32:25.201069
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    ## 23: 2026-08-25 12:32:25.170186
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    ## 26: 2026-08-25 12:32:25.170186
    ## 27: 2026-08-25 12:32:25.170186
    ## 28: 2026-08-25 12:32:25.170186
    ## 29: 2026-08-25 12:32:25.170186
    ## 30: 2026-08-25 12:32:25.170186
    ## 31: 2026-08-25 12:32:25.170186
    ## 32: 2026-08-25 12:32:25.175813
    ## 33: 2026-08-25 12:32:25.206368
    ## 34: 2026-08-25 12:32:25.241488
    ## 35: 2026-08-25 12:32:25.241488
    ## 36: 2026-08-25 12:32:25.241488
    ## 37: 2026-08-25 12:32:25.241488
    ## 38: 2026-08-25 12:32:25.241488
    ## 39: 2026-08-25 12:32:25.241488
    ## 40: 2026-08-25 12:32:25.241488
    ## 41: 2026-08-25 12:32:25.241488
    ## 42: 2026-08-25 12:32:25.241488
    ## 43: 2026-08-25 12:32:25.241488
    ## 44: 2026-08-25 12:32:25.241488
    ## 45: 2026-08-25 12:32:25.241488
    ## 46: 2026-08-25 12:32:25.241488
    ## 47: 2026-08-25 12:32:25.241488
    ## 48:  2026-08-25 12:32:25.21155
    ## 49:  2026-08-25 12:32:25.21155
    ## 50:  2026-08-25 12:32:25.21155
    ## 51:  2026-08-25 12:32:25.21155
    ## 52:  2026-08-25 12:32:25.21155
    ## 53:  2026-08-25 12:32:25.21155
    ## 54:  2026-08-25 12:32:25.21155
    ## 55:  2026-08-25 12:32:25.21155
    ## 56:  2026-08-25 12:32:25.21155
    ## 57:  2026-08-25 12:32:25.21155
    ## 58:  2026-08-25 12:32:25.21155
    ## 59:  2026-08-25 12:32:25.21155
    ## 60:  2026-08-25 12:32:25.21155
    ## 61:  2026-08-25 12:32:25.18904
    ## 62:  2026-08-25 12:32:25.18904
    ## 63:  2026-08-25 12:32:25.18904
    ## 64:  2026-08-25 12:32:25.18904
    ## 65:  2026-08-25 12:32:25.18904
    ## 66:  2026-08-25 12:32:25.18904
    ## 67:  2026-08-25 12:32:25.18904
    ## 68:  2026-08-25 12:32:25.18904
    ## 69:  2026-08-25 12:32:25.18904
    ## 70:  2026-08-25 12:32:25.18904
    ## 71:  2026-08-25 12:32:25.18904
    ## 72:  2026-08-25 12:32:25.18904
    ## 73:  2026-08-25 12:32:25.18904
    ## 74:  2026-08-25 12:32:25.18904
    ## 75:  2026-08-25 12:32:25.18904
    ## 76:  2026-08-25 12:32:25.18904
    ## 77:  2026-08-25 12:32:25.18904
    ## 78:  2026-08-25 12:32:25.18904
    ##                    createdDate
    ##                         <char>

    clearCache(tmpDir, ask = FALSE)

#### 1.3.1.2 Example 2: using the “accessed” tag

    ranNumsA <- rnorm(4) |> Cache(cachePath = tmpDir, userTags = "objectName:a")

    ## Saved! Cache file: adf21923cd1e50d0.rds; fn: rnorm

    ranNumsB <- runif(4) |> Cache(cachePath = tmpDir, userTags = "objectName:b")

    ## Saved! Cache file: e23cab430872a0ea.rds; fn: runif

    # access it again, from Cache
    Sys.sleep(1)
    ranNumsA <- rnorm(4) |> Cache(cachePath = tmpDir, userTags = "objectName:a")

    ## Object to retrieve (fn: rnorm, adf21923cd1e50d0.rds) ...

    ## Loaded! Cached result from previous rnorm call

    wholeCache <- showCache(tmpDir)

    ## Cache size:

    ## Total (including Rasters): 40 bytes

    ## Selected objects (not including Rasters): 40 bytes

    # keep only items accessed "recently" (i.e., only objectName:a)
    onlyRecentlyAccessed <- showCache(tmpDir, userTags = max(wholeCache[tagKey == "accessed"]$tagValue))

    ## Cache size:

    ## Total (including Rasters): 40 bytes

    ## Selected objects (not including Rasters): 40 bytes

    # inverse join with 2 data.tables ... using: a[!b]
    # i.e., return all of wholeCache that was not recently accessed
    #   Note: the two different ways to access -- old way with "artifact" will be deprecated
    toRemove <- unique(wholeCache[!onlyRecentlyAccessed, on = "cacheId"], by = "cacheId")$cacheId
    clearCache(tmpDir, toRemove, ask = FALSE) # remove ones not recently accessed

    ## Cache size:

    ## Total (including Rasters): 40 bytes

    ## Selected objects (not including Rasters): 40 bytes

    showCache(tmpDir) # still has more recently accessed

    ## Empty data.table (0 rows and 4 cols): cacheId,tagKey,tagValue,createdDate

#### 1.3.1.3 Example 3: using keepCache

`keepCache` does the same as previous example, but more simply.

    ranNumsA <- rnorm(4) |> Cache(cachePath = tmpDir, userTags = "objectName:a")

    ## Saved! Cache file: adf21923cd1e50d0.rds; fn: rnorm

    ranNumsB <- Cache(runif(4)) |> Cache(cachePath = tmpDir, userTags = "objectName:b")

    ## No cachePath supplied and getOption('reproducible.cachePath') is inside a temporary directory;
    ##   this will not persist across R sessions.

    ## Saved! Cache file: e23cab430872a0ea.rds; fn: runif

    ## Saved! Cache file: 490aec1962b296c0.rds; fn: Cache

    # keep only those cached items from the last 24 hours
    oneDay <- 60 * 60 * 24
    keepCache(tmpDir, after = Sys.time() - oneDay, ask = FALSE)

    ## Nothing to remove; keeping all

    ##              cacheId              tagKey                         tagValue
    ##               <char>              <char>                           <char>
    ##  1: 490aec1962b296c0            function                            Cache
    ##  2: 490aec1962b296c0          objectName                                b
    ##  3: 490aec1962b296c0            accessed        2026-08-25 12:32:26.39868
    ##  4: 490aec1962b296c0             inCloud                            FALSE
    ##  5: 490aec1962b296c0   elapsedTimeDigest                 0.002314568 secs
    ##  6: 490aec1962b296c0           preDigest             FUN:b776a5e68c999a5c
    ##  7: 490aec1962b296c0           preDigest cacheSaveFormat:cf2828ea967d53e7
    ##  8: 490aec1962b296c0           preDigest          dryRun:e9aac936a0e8f6ae
    ##  9: 490aec1962b296c0           preDigest            .FUN:53b64a48c1458486
    ## 10: 490aec1962b296c0           preDigest  .cacheChaining:71681d621365dfd7
    ## 11: 490aec1962b296c0           preDigest     .cacheExtra:c85d88fc56f4e042
    ## 12: 490aec1962b296c0           preDigest   .functionName:c85d88fc56f4e042
    ## 13: 490aec1962b296c0           preDigest            conn:118387d5d48f757d
    ## 14: 490aec1962b296c0           preDigest             drv:9ce9a83896bf68a1
    ## 15: 490aec1962b296c0               class                          numeric
    ## 16: 490aec1962b296c0         object.size                             1008
    ## 17: 490aec1962b296c0            fromDisk                            FALSE
    ## 18: 490aec1962b296c0          resultHash
    ## 19: 490aec1962b296c0 elapsedTimeFirstRun                  0.01026273 secs
    ## 20: adf21923cd1e50d0            function                            rnorm
    ## 21: adf21923cd1e50d0          objectName                                a
    ## 22: adf21923cd1e50d0            accessed        2026-08-25 12:32:26.39206
    ## 23: adf21923cd1e50d0             inCloud                            FALSE
    ## 24: adf21923cd1e50d0   elapsedTimeDigest                 0.001374006 secs
    ## 25: adf21923cd1e50d0           preDigest            .FUN:4f604aa46882b368
    ## 26: adf21923cd1e50d0           preDigest            mean:c40c00762a0dac94
    ## 27: adf21923cd1e50d0           preDigest               n:7eef4eae85fd9229
    ## 28: adf21923cd1e50d0           preDigest              sd:853b1797f54b229c
    ## 29: adf21923cd1e50d0               class                          numeric
    ## 30: adf21923cd1e50d0         object.size                               80
    ## 31: adf21923cd1e50d0            fromDisk                            FALSE
    ## 32: adf21923cd1e50d0          resultHash
    ## 33: adf21923cd1e50d0 elapsedTimeFirstRun                0.0009999275 secs
    ##              cacheId              tagKey                         tagValue
    ##               <char>              <char>                           <char>
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:26.409805
    ##  2: 2026-08-25 12:32:26.409805
    ##  3: 2026-08-25 12:32:26.409805
    ##  4: 2026-08-25 12:32:26.409805
    ##  5: 2026-08-25 12:32:26.409805
    ##  6: 2026-08-25 12:32:26.409805
    ##  7: 2026-08-25 12:32:26.409805
    ##  8: 2026-08-25 12:32:26.409805
    ##  9: 2026-08-25 12:32:26.409805
    ## 10: 2026-08-25 12:32:26.409805
    ## 11: 2026-08-25 12:32:26.409805
    ## 12: 2026-08-25 12:32:26.409805
    ## 13: 2026-08-25 12:32:26.409805
    ## 14: 2026-08-25 12:32:26.409805
    ## 15: 2026-08-25 12:32:26.409805
    ## 16: 2026-08-25 12:32:26.409805
    ## 17: 2026-08-25 12:32:26.409805
    ## 18: 2026-08-25 12:32:26.409805
    ## 19: 2026-08-25 12:32:26.409805
    ## 20: 2026-08-25 12:32:26.393953
    ## 21: 2026-08-25 12:32:26.393953
    ## 22: 2026-08-25 12:32:26.393953
    ## 23: 2026-08-25 12:32:26.393953
    ## 24: 2026-08-25 12:32:26.393953
    ## 25: 2026-08-25 12:32:26.393953
    ## 26: 2026-08-25 12:32:26.393953
    ## 27: 2026-08-25 12:32:26.393953
    ## 28: 2026-08-25 12:32:26.393953
    ## 29: 2026-08-25 12:32:26.393953
    ## 30: 2026-08-25 12:32:26.393953
    ## 31: 2026-08-25 12:32:26.393953
    ## 32: 2026-08-25 12:32:26.393953
    ## 33: 2026-08-25 12:32:26.393953
    ##                    createdDate
    ##                         <char>

    # Keep all Cache items created with an rnorm() call
    keepCache(tmpDir, userTags = "rnorm", ask = FALSE)

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: adf21923cd1e50d0            function                     rnorm
    ##  2: adf21923cd1e50d0          objectName                         a
    ##  3: adf21923cd1e50d0            accessed 2026-08-25 12:32:26.39206
    ##  4: adf21923cd1e50d0             inCloud                     FALSE
    ##  5: adf21923cd1e50d0   elapsedTimeDigest          0.001374006 secs
    ##  6: adf21923cd1e50d0           preDigest     .FUN:4f604aa46882b368
    ##  7: adf21923cd1e50d0           preDigest     mean:c40c00762a0dac94
    ##  8: adf21923cd1e50d0           preDigest        n:7eef4eae85fd9229
    ##  9: adf21923cd1e50d0           preDigest       sd:853b1797f54b229c
    ## 10: adf21923cd1e50d0               class                   numeric
    ## 11: adf21923cd1e50d0         object.size                        80
    ## 12: adf21923cd1e50d0            fromDisk                     FALSE
    ## 13: adf21923cd1e50d0          resultHash
    ## 14: adf21923cd1e50d0 elapsedTimeFirstRun         0.0009999275 secs
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:26.393953
    ##  2: 2026-08-25 12:32:26.393953
    ##  3: 2026-08-25 12:32:26.393953
    ##  4: 2026-08-25 12:32:26.393953
    ##  5: 2026-08-25 12:32:26.393953
    ##  6: 2026-08-25 12:32:26.393953
    ##  7: 2026-08-25 12:32:26.393953
    ##  8: 2026-08-25 12:32:26.393953
    ##  9: 2026-08-25 12:32:26.393953
    ## 10: 2026-08-25 12:32:26.393953
    ## 11: 2026-08-25 12:32:26.393953
    ## 12: 2026-08-25 12:32:26.393953
    ## 13: 2026-08-25 12:32:26.393953
    ## 14: 2026-08-25 12:32:26.393953

    showCache(tmpDir)

    ## Cache size:

    ## Total (including Rasters): 20 bytes

    ## Selected objects (not including Rasters): 20 bytes

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: adf21923cd1e50d0            function                     rnorm
    ##  2: adf21923cd1e50d0          objectName                         a
    ##  3: adf21923cd1e50d0            accessed 2026-08-25 12:32:26.39206
    ##  4: adf21923cd1e50d0             inCloud                     FALSE
    ##  5: adf21923cd1e50d0   elapsedTimeDigest          0.001374006 secs
    ##  6: adf21923cd1e50d0           preDigest     .FUN:4f604aa46882b368
    ##  7: adf21923cd1e50d0           preDigest     mean:c40c00762a0dac94
    ##  8: adf21923cd1e50d0           preDigest        n:7eef4eae85fd9229
    ##  9: adf21923cd1e50d0           preDigest       sd:853b1797f54b229c
    ## 10: adf21923cd1e50d0               class                   numeric
    ## 11: adf21923cd1e50d0         object.size                        80
    ## 12: adf21923cd1e50d0            fromDisk                     FALSE
    ## 13: adf21923cd1e50d0          resultHash
    ## 14: adf21923cd1e50d0 elapsedTimeFirstRun         0.0009999275 secs
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:26.393953
    ##  2: 2026-08-25 12:32:26.393953
    ##  3: 2026-08-25 12:32:26.393953
    ##  4: 2026-08-25 12:32:26.393953
    ##  5: 2026-08-25 12:32:26.393953
    ##  6: 2026-08-25 12:32:26.393953
    ##  7: 2026-08-25 12:32:26.393953
    ##  8: 2026-08-25 12:32:26.393953
    ##  9: 2026-08-25 12:32:26.393953
    ## 10: 2026-08-25 12:32:26.393953
    ## 11: 2026-08-25 12:32:26.393953
    ## 12: 2026-08-25 12:32:26.393953
    ## 13: 2026-08-25 12:32:26.393953
    ## 14: 2026-08-25 12:32:26.393953

    # Remove all Cache items that happened within a rnorm() call
    clearCache(tmpDir, userTags = "rnorm", ask = FALSE)

    ## Cache size:

    ## Total (including Rasters): 20 bytes

    ## Selected objects (not including Rasters): 20 bytes

    showCache(tmpDir) ## empty

    ## Empty data.table (0 rows and 4 cols): cacheId,tagKey,tagValue,createdDate

    # Also, can set a time before caching happens and remove based on this
    #  --> a useful, simple way to control Cache
    ranNumsA <- rnorm(4) |> Cache(cachePath = tmpDir, userTags = "objectName:a")

    ## Saved! Cache file: adf21923cd1e50d0.rds; fn: rnorm

    startTime <- Sys.time()
    Sys.sleep(1)
    ranNumsB <- rnorm(5) |> Cache(cachePath = tmpDir, userTags = "objectName:b")

    ## Saved! Cache file: 438a3028a4570cf9.rds; fn: rnorm

    keepCache(tmpDir, after = startTime, ask = FALSE) # keep only those newer than startTime

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: 438a3028a4570cf9            function                     rnorm
    ##  2: 438a3028a4570cf9          objectName                         b
    ##  3: 438a3028a4570cf9            accessed 2026-08-25 12:32:27.47876
    ##  4: 438a3028a4570cf9             inCloud                     FALSE
    ##  5: 438a3028a4570cf9   elapsedTimeDigest          0.001604557 secs
    ##  6: 438a3028a4570cf9           preDigest     .FUN:4f604aa46882b368
    ##  7: 438a3028a4570cf9           preDigest     mean:c40c00762a0dac94
    ##  8: 438a3028a4570cf9           preDigest        n:a4f076b3db622faf
    ##  9: 438a3028a4570cf9           preDigest       sd:853b1797f54b229c
    ## 10: 438a3028a4570cf9               class                   numeric
    ## 11: 438a3028a4570cf9         object.size                        96
    ## 12: 438a3028a4570cf9            fromDisk                     FALSE
    ## 13: 438a3028a4570cf9          resultHash
    ## 14: 438a3028a4570cf9 elapsedTimeFirstRun          0.001115084 secs
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:27.480931
    ##  2: 2026-08-25 12:32:27.480931
    ##  3: 2026-08-25 12:32:27.480931
    ##  4: 2026-08-25 12:32:27.480931
    ##  5: 2026-08-25 12:32:27.480931
    ##  6: 2026-08-25 12:32:27.480931
    ##  7: 2026-08-25 12:32:27.480931
    ##  8: 2026-08-25 12:32:27.480931
    ##  9: 2026-08-25 12:32:27.480931
    ## 10: 2026-08-25 12:32:27.480931
    ## 11: 2026-08-25 12:32:27.480931
    ## 12: 2026-08-25 12:32:27.480931
    ## 13: 2026-08-25 12:32:27.480931
    ## 14: 2026-08-25 12:32:27.480931

    clearCache(tmpDir, ask = FALSE)

#### 1.3.1.4 Example 4: searching for multiple objects in the cache

    # default userTags is "and" matching; for "or" matching use |
    ranNumsA <- runif(4) |> Cache(cachePath = tmpDir, userTags = "objectName:a")

    ## Saved! Cache file: e23cab430872a0ea.rds; fn: runif

    ranNumsB <- rnorm(4) |> Cache(cachePath = tmpDir, userTags = "objectName:b")

    ## Saved! Cache file: adf21923cd1e50d0.rds; fn: rnorm

    # show all objects (runif and rnorm in this case)
    showCache(tmpDir)

    ## Cache size:

    ## Total (including Rasters): 40 bytes

    ## Selected objects (not including Rasters): 40 bytes

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: adf21923cd1e50d0            function                     rnorm
    ##  2: adf21923cd1e50d0          objectName                         b
    ##  3: adf21923cd1e50d0            accessed 2026-08-25 12:32:27.54061
    ##  4: adf21923cd1e50d0             inCloud                     FALSE
    ##  5: adf21923cd1e50d0   elapsedTimeDigest          0.001491308 secs
    ##  6: adf21923cd1e50d0           preDigest     .FUN:4f604aa46882b368
    ##  7: adf21923cd1e50d0           preDigest     mean:c40c00762a0dac94
    ##  8: adf21923cd1e50d0           preDigest        n:7eef4eae85fd9229
    ##  9: adf21923cd1e50d0           preDigest       sd:853b1797f54b229c
    ## 10: adf21923cd1e50d0               class                   numeric
    ## 11: adf21923cd1e50d0         object.size                        80
    ## 12: adf21923cd1e50d0            fromDisk                     FALSE
    ## 13: adf21923cd1e50d0          resultHash
    ## 14: adf21923cd1e50d0 elapsedTimeFirstRun         0.0009975433 secs
    ## 15: e23cab430872a0ea            function                     runif
    ## 16: e23cab430872a0ea          objectName                         a
    ## 17: e23cab430872a0ea            accessed 2026-08-25 12:32:27.53457
    ## 18: e23cab430872a0ea             inCloud                     FALSE
    ## 19: e23cab430872a0ea   elapsedTimeDigest          0.001501322 secs
    ## 20: e23cab430872a0ea           preDigest     .FUN:881ec847b7161f3c
    ## 21: e23cab430872a0ea           preDigest      max:853b1797f54b229c
    ## 22: e23cab430872a0ea           preDigest      min:c40c00762a0dac94
    ## 23: e23cab430872a0ea           preDigest        n:7eef4eae85fd9229
    ## 24: e23cab430872a0ea               class                   numeric
    ## 25: e23cab430872a0ea         object.size                        80
    ## 26: e23cab430872a0ea            fromDisk                     FALSE
    ## 27: e23cab430872a0ea          resultHash
    ## 28: e23cab430872a0ea elapsedTimeFirstRun           0.00103116 secs
    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:27.542528
    ##  2: 2026-08-25 12:32:27.542528
    ##  3: 2026-08-25 12:32:27.542528
    ##  4: 2026-08-25 12:32:27.542528
    ##  5: 2026-08-25 12:32:27.542528
    ##  6: 2026-08-25 12:32:27.542528
    ##  7: 2026-08-25 12:32:27.542528
    ##  8: 2026-08-25 12:32:27.542528
    ##  9: 2026-08-25 12:32:27.542528
    ## 10: 2026-08-25 12:32:27.542528
    ## 11: 2026-08-25 12:32:27.542528
    ## 12: 2026-08-25 12:32:27.542528
    ## 13: 2026-08-25 12:32:27.542528
    ## 14: 2026-08-25 12:32:27.542528
    ## 15: 2026-08-25 12:32:27.536555
    ## 16: 2026-08-25 12:32:27.536555
    ## 17: 2026-08-25 12:32:27.536555
    ## 18: 2026-08-25 12:32:27.536555
    ## 19: 2026-08-25 12:32:27.536555
    ## 20: 2026-08-25 12:32:27.536555
    ## 21: 2026-08-25 12:32:27.536555
    ## 22: 2026-08-25 12:32:27.536555
    ## 23: 2026-08-25 12:32:27.536555
    ## 24: 2026-08-25 12:32:27.536555
    ## 25: 2026-08-25 12:32:27.536555
    ## 26: 2026-08-25 12:32:27.536555
    ## 27: 2026-08-25 12:32:27.536555
    ## 28: 2026-08-25 12:32:27.536555
    ##                    createdDate
    ##                         <char>

    # show objects that are both runif and rnorm
    # (i.e., none in this case, because objecs are either or, not both)
    showCache(tmpDir, userTags = c("runif", "rnorm")) ## empty

    ## Cache size:

    ## Total (including Rasters): 0 bytes

    ## Selected objects (not including Rasters): 0 bytes

    ## Empty data.table (0 rows and 4 cols): cacheId,tagKey,tagValue,createdDate

    # show objects that are either runif or rnorm ("or" search)
    showCache(tmpDir, userTags = "runif|rnorm")

    ## Cache size:

    ## Total (including Rasters): 40 bytes

    ## Selected objects (not including Rasters): 40 bytes

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: adf21923cd1e50d0            function                     rnorm
    ##  2: adf21923cd1e50d0          objectName                         b
    ##  3: adf21923cd1e50d0            accessed 2026-08-25 12:32:27.54061
    ##  4: adf21923cd1e50d0             inCloud                     FALSE
    ##  5: adf21923cd1e50d0   elapsedTimeDigest          0.001491308 secs
    ##  6: adf21923cd1e50d0           preDigest     .FUN:4f604aa46882b368
    ##  7: adf21923cd1e50d0           preDigest     mean:c40c00762a0dac94
    ##  8: adf21923cd1e50d0           preDigest        n:7eef4eae85fd9229
    ##  9: adf21923cd1e50d0           preDigest       sd:853b1797f54b229c
    ## 10: adf21923cd1e50d0               class                   numeric
    ## 11: adf21923cd1e50d0         object.size                        80
    ## 12: adf21923cd1e50d0            fromDisk                     FALSE
    ## 13: adf21923cd1e50d0          resultHash
    ## 14: adf21923cd1e50d0 elapsedTimeFirstRun         0.0009975433 secs
    ## 15: e23cab430872a0ea            function                     runif
    ## 16: e23cab430872a0ea          objectName                         a
    ## 17: e23cab430872a0ea            accessed 2026-08-25 12:32:27.53457
    ## 18: e23cab430872a0ea             inCloud                     FALSE
    ## 19: e23cab430872a0ea   elapsedTimeDigest          0.001501322 secs
    ## 20: e23cab430872a0ea           preDigest     .FUN:881ec847b7161f3c
    ## 21: e23cab430872a0ea           preDigest      max:853b1797f54b229c
    ## 22: e23cab430872a0ea           preDigest      min:c40c00762a0dac94
    ## 23: e23cab430872a0ea           preDigest        n:7eef4eae85fd9229
    ## 24: e23cab430872a0ea               class                   numeric
    ## 25: e23cab430872a0ea         object.size                        80
    ## 26: e23cab430872a0ea            fromDisk                     FALSE
    ## 27: e23cab430872a0ea          resultHash
    ## 28: e23cab430872a0ea elapsedTimeFirstRun           0.00103116 secs
    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:27.542528
    ##  2: 2026-08-25 12:32:27.542528
    ##  3: 2026-08-25 12:32:27.542528
    ##  4: 2026-08-25 12:32:27.542528
    ##  5: 2026-08-25 12:32:27.542528
    ##  6: 2026-08-25 12:32:27.542528
    ##  7: 2026-08-25 12:32:27.542528
    ##  8: 2026-08-25 12:32:27.542528
    ##  9: 2026-08-25 12:32:27.542528
    ## 10: 2026-08-25 12:32:27.542528
    ## 11: 2026-08-25 12:32:27.542528
    ## 12: 2026-08-25 12:32:27.542528
    ## 13: 2026-08-25 12:32:27.542528
    ## 14: 2026-08-25 12:32:27.542528
    ## 15: 2026-08-25 12:32:27.536555
    ## 16: 2026-08-25 12:32:27.536555
    ## 17: 2026-08-25 12:32:27.536555
    ## 18: 2026-08-25 12:32:27.536555
    ## 19: 2026-08-25 12:32:27.536555
    ## 20: 2026-08-25 12:32:27.536555
    ## 21: 2026-08-25 12:32:27.536555
    ## 22: 2026-08-25 12:32:27.536555
    ## 23: 2026-08-25 12:32:27.536555
    ## 24: 2026-08-25 12:32:27.536555
    ## 25: 2026-08-25 12:32:27.536555
    ## 26: 2026-08-25 12:32:27.536555
    ## 27: 2026-08-25 12:32:27.536555
    ## 28: 2026-08-25 12:32:27.536555
    ##                    createdDate
    ##                         <char>

    # keep only objects that are either runif or rnorm ("or" search)
    keepCache(tmpDir, userTags = "runif|rnorm", ask = FALSE)

    ## Nothing to remove; keeping all

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: adf21923cd1e50d0            function                     rnorm
    ##  2: adf21923cd1e50d0          objectName                         b
    ##  3: adf21923cd1e50d0            accessed 2026-08-25 12:32:27.54061
    ##  4: adf21923cd1e50d0             inCloud                     FALSE
    ##  5: adf21923cd1e50d0   elapsedTimeDigest          0.001491308 secs
    ##  6: adf21923cd1e50d0           preDigest     .FUN:4f604aa46882b368
    ##  7: adf21923cd1e50d0           preDigest     mean:c40c00762a0dac94
    ##  8: adf21923cd1e50d0           preDigest        n:7eef4eae85fd9229
    ##  9: adf21923cd1e50d0           preDigest       sd:853b1797f54b229c
    ## 10: adf21923cd1e50d0               class                   numeric
    ## 11: adf21923cd1e50d0         object.size                        80
    ## 12: adf21923cd1e50d0            fromDisk                     FALSE
    ## 13: adf21923cd1e50d0          resultHash
    ## 14: adf21923cd1e50d0 elapsedTimeFirstRun         0.0009975433 secs
    ## 15: e23cab430872a0ea            function                     runif
    ## 16: e23cab430872a0ea          objectName                         a
    ## 17: e23cab430872a0ea            accessed 2026-08-25 12:32:27.53457
    ## 18: e23cab430872a0ea             inCloud                     FALSE
    ## 19: e23cab430872a0ea   elapsedTimeDigest          0.001501322 secs
    ## 20: e23cab430872a0ea           preDigest     .FUN:881ec847b7161f3c
    ## 21: e23cab430872a0ea           preDigest      max:853b1797f54b229c
    ## 22: e23cab430872a0ea           preDigest      min:c40c00762a0dac94
    ## 23: e23cab430872a0ea           preDigest        n:7eef4eae85fd9229
    ## 24: e23cab430872a0ea               class                   numeric
    ## 25: e23cab430872a0ea         object.size                        80
    ## 26: e23cab430872a0ea            fromDisk                     FALSE
    ## 27: e23cab430872a0ea          resultHash
    ## 28: e23cab430872a0ea elapsedTimeFirstRun           0.00103116 secs
    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:27.542528
    ##  2: 2026-08-25 12:32:27.542528
    ##  3: 2026-08-25 12:32:27.542528
    ##  4: 2026-08-25 12:32:27.542528
    ##  5: 2026-08-25 12:32:27.542528
    ##  6: 2026-08-25 12:32:27.542528
    ##  7: 2026-08-25 12:32:27.542528
    ##  8: 2026-08-25 12:32:27.542528
    ##  9: 2026-08-25 12:32:27.542528
    ## 10: 2026-08-25 12:32:27.542528
    ## 11: 2026-08-25 12:32:27.542528
    ## 12: 2026-08-25 12:32:27.542528
    ## 13: 2026-08-25 12:32:27.542528
    ## 14: 2026-08-25 12:32:27.542528
    ## 15: 2026-08-25 12:32:27.536555
    ## 16: 2026-08-25 12:32:27.536555
    ## 17: 2026-08-25 12:32:27.536555
    ## 18: 2026-08-25 12:32:27.536555
    ## 19: 2026-08-25 12:32:27.536555
    ## 20: 2026-08-25 12:32:27.536555
    ## 21: 2026-08-25 12:32:27.536555
    ## 22: 2026-08-25 12:32:27.536555
    ## 23: 2026-08-25 12:32:27.536555
    ## 24: 2026-08-25 12:32:27.536555
    ## 25: 2026-08-25 12:32:27.536555
    ## 26: 2026-08-25 12:32:27.536555
    ## 27: 2026-08-25 12:32:27.536555
    ## 28: 2026-08-25 12:32:27.536555
    ##                    createdDate
    ##                         <char>

    clearCache(tmpDir, ask = FALSE)

#### 1.3.1.5 Example 5: using caching to speed up rerunning expensive computations

    ras <- terra::rast(terra::ext(0, 5, 0, 5),
      res = 1,
      vals = sample(1:5, replace = TRUE, size = 25),
      crs = "+proj=lcc +lat_1=48 +lat_2=33 +lon_0=-100 +ellps=WGS84"
    )

    rasCRS <- terra::crs(ras)
    # Build an explicit target raster (same CRS, coarser resolution).
    # Avoids the `terra::project(x, char_crs, res = N)` shorthand which
    # recurses internally and forwards an unrecognized `wopt` set on
    # recent terra versions, producing
    # `[write] unknown option(s): xscale,yscale`.
    rasTarget <- terra::rast(terra::ext(ras), crs = rasCRS, resolution = 5)

    # A slow operation, like GIS operation
    notCached <- suppressWarnings(
      # project raster generates warnings when run non-interactively
      terra::project(ras, rasTarget)
    )

    cached <- suppressWarnings(
      # project raster generates warnings when run non-interactively
      # using quote works also
      terra::project(ras, rasTarget) |> Cache(cachePath = tmpDir)
    )

    ## Saved! Cache file: c079976950f65dcb.rds; fn: project

    # second time is much faster
    reRun <- suppressWarnings(
      # project raster generates warnings when run non-interactively
      terra::project(ras, rasTarget) |> Cache(cachePath = tmpDir)
    )

    ## Object to retrieve (fn: project, c079976950f65dcb.rds) ...

    ## Loaded! Cached result from previous project call

    # recovered cached version is same as non-cached version
    all.equal(notCached, reRun, check.attributes = FALSE) ## TRUE

    ## [1] "Attributes: < Names: 2 string mismatches >"
    ## [2] "Attributes: < Length mismatch: comparison on first 2 components >"
    ## [3] "Attributes: < Component 1: Modes: character, list >"
    ## [4] "Attributes: < Component 1: names for current but not for target >"
    ## [5] "Attributes: < Component 1: Attributes: < names for target but not for current > >"
    ## [6] "Attributes: < Component 1: Attributes: < Length mismatch: comparison on first 0 components > >"
    ## [7] "Attributes: < Component 1: target is character, current is list >"
    ## [8] "Attributes: < Component 2: 'current' is not an envRefClass >"

### 1.3.2 Nested Caching

Nested caching, which is when Caching of a function occurs inside an outer function, which is itself cached. This is a critical element to working within a reproducible work flow. It is not enough during development to cache flat code chunks, as there will be many levels of “slow” functions. Ideally, at all points in a development cycle, it should be possible to get to any line of code starting from the very initial steps, running through everything up to that point, in less than a few seconds. If the workflow can be kept very fast like this, then there is a guarantee that it will work at any point.

    ##########################
    ## Nested Caching
    # Make 2 functions
    inner <- function(mean) {
      d <- 1
      rnorm(n = 3, mean = mean)
    }
    outer <- function(n) {
      inner(0.1) |> Cache(cachePath = tmpdir2)
    }

    # make 2 different cache paths
    tmpdir1 <- file.path(tempfile(), "first")
    tmpdir2 <- file.path(tempfile(), "second")

    # Run the Cache ... notOlderThan propagates to all 3 Cache calls,
    #   but cachePath is tmpdir1 in top level Cache and all nested
    #   Cache calls, unless individually overridden ... here inner
    #   uses tmpdir2 repository
    outer(n = 2) |> Cache(cachePath = tmpdir1)

    ## Saved! Cache file: a352d42cb0291199.rds; fn: inner

    ## Saved! Cache file: 61564dd5e84ab6d5.rds; fn: outer

    ## [1] -0.06425582 -0.77553437 -0.95058508
    ## attr(,".Cache")
    ## attr(,".Cache")$newCache
    ## [1] TRUE
    ##
    ## attr(,"tags")
    ## [1] "cacheId:61564dd5e84ab6d5"
    ## attr(,"callInCache")
    ## [1] ""

    showCache(tmpdir1) # 2 function calls

    ## Cache size:

    ## Total (including Rasters): 252 bytes

    ## Selected objects (not including Rasters): 252 bytes

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: 61564dd5e84ab6d5            function                     outer
    ##  2: 61564dd5e84ab6d5            accessed 2026-08-25 12:32:27.74703
    ##  3: 61564dd5e84ab6d5             inCloud                     FALSE
    ##  4: 61564dd5e84ab6d5   elapsedTimeDigest          0.001439095 secs
    ##  5: 61564dd5e84ab6d5           preDigest     .FUN:fd3ff16451bebbef
    ##  6: 61564dd5e84ab6d5           preDigest        n:82dc709f2b91918a
    ##  7: 61564dd5e84ab6d5               class                   numeric
    ##  8: 61564dd5e84ab6d5         object.size                      1008
    ##  9: 61564dd5e84ab6d5            fromDisk                     FALSE
    ## 10: 61564dd5e84ab6d5          resultHash
    ## 11: 61564dd5e84ab6d5 elapsedTimeFirstRun          0.005897045 secs
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:27.753873
    ##  2: 2026-08-25 12:32:27.753873
    ##  3: 2026-08-25 12:32:27.753873
    ##  4: 2026-08-25 12:32:27.753873
    ##  5: 2026-08-25 12:32:27.753873
    ##  6: 2026-08-25 12:32:27.753873
    ##  7: 2026-08-25 12:32:27.753873
    ##  8: 2026-08-25 12:32:27.753873
    ##  9: 2026-08-25 12:32:27.753873
    ## 10: 2026-08-25 12:32:27.753873
    ## 11: 2026-08-25 12:32:27.753873

    showCache(tmpdir2) # 1 function call

    ## Cache size:

    ## Total (including Rasters): 20 bytes

    ## Selected objects (not including Rasters): 20 bytes

    ##              cacheId              tagKey                  tagValue
    ##               <char>              <char>                    <char>
    ##  1: a352d42cb0291199            function                     inner
    ##  2: a352d42cb0291199       outerFunction                     outer
    ##  3: a352d42cb0291199            accessed 2026-08-25 12:32:27.74977
    ##  4: a352d42cb0291199             inCloud                     FALSE
    ##  5: a352d42cb0291199   elapsedTimeDigest          0.001401424 secs
    ##  6: a352d42cb0291199           preDigest     .FUN:c411a17f70613a02
    ##  7: a352d42cb0291199           preDigest     mean:22413394efd9f6a3
    ##  8: a352d42cb0291199               class                   numeric
    ##  9: a352d42cb0291199         object.size                        80
    ## 10: a352d42cb0291199            fromDisk                     FALSE
    ## 11: a352d42cb0291199          resultHash
    ## 12: a352d42cb0291199 elapsedTimeFirstRun         0.0008907318 secs
    ##                  createdDate
    ##                       <char>
    ##  1: 2026-08-25 12:32:27.7515
    ##  2: 2026-08-25 12:32:27.7515
    ##  3: 2026-08-25 12:32:27.7515
    ##  4: 2026-08-25 12:32:27.7515
    ##  5: 2026-08-25 12:32:27.7515
    ##  6: 2026-08-25 12:32:27.7515
    ##  7: 2026-08-25 12:32:27.7515
    ##  8: 2026-08-25 12:32:27.7515
    ##  9: 2026-08-25 12:32:27.7515
    ## 10: 2026-08-25 12:32:27.7515
    ## 11: 2026-08-25 12:32:27.7515
    ## 12: 2026-08-25 12:32:27.7515

    # userTags get appended
    # all items have the outer tag propagate, plus inner ones only have inner ones
    clearCache(tmpdir1, ask = FALSE)
    outerTag <- "outerTag"
    innerTag <- "innerTag"
    inner <- function(mean) {
      d <- 1
      rnorm(n = 3, mean = mean) |> Cache(notOlderThan = Sys.time() - 1e5, userTags = innerTag)
    }
    outer <- function(n) {
      inner(0.1) |> Cache()
    }
    aa <- Cache(outer, n = 2) |> Cache(cachePath = tmpdir1, userTags = outerTag)

    ## No cachePath supplied and getOption('reproducible.cachePath') is inside a temporary directory;
    ##   this will not persist across R sessions.

    ## No cachePath supplied and getOption('reproducible.cachePath') is inside a temporary directory;
    ##   this will not persist across R sessions.
    ## No cachePath supplied and getOption('reproducible.cachePath') is inside a temporary directory;
    ##   this will not persist across R sessions.

    ## Saved! Cache file: a481e2b85f7337f2.rds; fn: rnorm

    ## Saved! Cache file: 9691c7bae9ad6582.rds; fn: inner

    ## Saved! Cache file: 2d26a68d5154433e.rds; fn: outer

    ## Saved! Cache file: 2a8f39be7cce97cd.rds; fn: Cache

    showCache(tmpdir1) # rnorm function has outerTag and innerTag, inner and outer only have outerTag

    ## Cache size:

    ## Total (including Rasters): 252 bytes

    ## Selected objects (not including Rasters): 252 bytes

    ##              cacheId              tagKey                         tagValue
    ##               <char>              <char>                           <char>
    ##  1: 2a8f39be7cce97cd            function                            Cache
    ##  2: 2a8f39be7cce97cd            userTags                         outerTag
    ##  3: 2a8f39be7cce97cd            accessed        2026-08-25 12:32:27.76980
    ##  4: 2a8f39be7cce97cd             inCloud                            FALSE
    ##  5: 2a8f39be7cce97cd   elapsedTimeDigest                 0.002250671 secs
    ##  6: 2a8f39be7cce97cd           preDigest             FUN:f4ab56347506d214
    ##  7: 2a8f39be7cce97cd           preDigest cacheSaveFormat:cf2828ea967d53e7
    ##  8: 2a8f39be7cce97cd           preDigest          dryRun:e9aac936a0e8f6ae
    ##  9: 2a8f39be7cce97cd           preDigest            .FUN:53b64a48c1458486
    ## 10: 2a8f39be7cce97cd           preDigest  .cacheChaining:71681d621365dfd7
    ## 11: 2a8f39be7cce97cd           preDigest     .cacheExtra:c85d88fc56f4e042
    ## 12: 2a8f39be7cce97cd           preDigest   .functionName:c85d88fc56f4e042
    ## 13: 2a8f39be7cce97cd           preDigest            conn:118387d5d48f757d
    ## 14: 2a8f39be7cce97cd           preDigest             drv:9ce9a83896bf68a1
    ## 15: 2a8f39be7cce97cd           preDigest               n:82dc709f2b91918a
    ## 16: 2a8f39be7cce97cd               class                          numeric
    ## 17: 2a8f39be7cce97cd         object.size                             1008
    ## 18: 2a8f39be7cce97cd            fromDisk                            FALSE
    ## 19: 2a8f39be7cce97cd          resultHash
    ## 20: 2a8f39be7cce97cd elapsedTimeFirstRun                  0.01877427 secs
    ##              cacheId              tagKey                         tagValue
    ##               <char>              <char>                           <char>
    ##                    createdDate
    ##                         <char>
    ##  1: 2026-08-25 12:32:27.789481
    ##  2: 2026-08-25 12:32:27.789481
    ##  3: 2026-08-25 12:32:27.789481
    ##  4: 2026-08-25 12:32:27.789481
    ##  5: 2026-08-25 12:32:27.789481
    ##  6: 2026-08-25 12:32:27.789481
    ##  7: 2026-08-25 12:32:27.789481
    ##  8: 2026-08-25 12:32:27.789481
    ##  9: 2026-08-25 12:32:27.789481
    ## 10: 2026-08-25 12:32:27.789481
    ## 11: 2026-08-25 12:32:27.789481
    ## 12: 2026-08-25 12:32:27.789481
    ## 13: 2026-08-25 12:32:27.789481
    ## 14: 2026-08-25 12:32:27.789481
    ## 15: 2026-08-25 12:32:27.789481
    ## 16: 2026-08-25 12:32:27.789481
    ## 17: 2026-08-25 12:32:27.789481
    ## 18: 2026-08-25 12:32:27.789481
    ## 19: 2026-08-25 12:32:27.789481
    ## 20: 2026-08-25 12:32:27.789481
    ##                    createdDate
    ##                         <char>

### 1.3.3 cacheId

Sometimes, it is not absolutely desirable to maintain the work flow intact because changes that are irrelevant to the analysis, such as changing messages sent to a user, may be changed, without a desire to rerun functions. The `cacheId` argument is for this. Once a piece of code is run, then the `cacheId` can be manually extracted (it is reported at the end of a Cache call) and manually placed in the code, passed in as, say, `cacheId = "ad184ce64541972b50afd8e7b75f821b"`.

    ### cacheId
    set.seed(1)
    rnorm(1) |> Cache(cachePath = tmpdir1)

    ## Saved! Cache file: ca275879d5116967.rds; fn: rnorm

    ## [1] -0.6264538
    ## attr(,".Cache")
    ## attr(,".Cache")$newCache
    ## [1] TRUE
    ##
    ## attr(,"tags")
    ## [1] "cacheId:ca275879d5116967"
    ## attr(,"callInCache")
    ## [1] ""

    # manually look at output attribute which shows cacheId: 422bae4ed2f770cc
    rnorm(1) |> Cache(cachePath = tmpdir1, cacheId = "422bae4ed2f770cc") # same value

    ## cacheId passed to override automatic digesting; using 422bae4ed2f770cc

    ## Saved! Cache file: 422bae4ed2f770cc.rds; fn: rnorm

    ## [1] 0.1836433
    ## attr(,".Cache")
    ## attr(,".Cache")$newCache
    ## [1] TRUE
    ##
    ## attr(,"tags")
    ## [1] "cacheId:422bae4ed2f770cc"
    ## attr(,"callInCache")
    ## [1] ""

    # override even with different inputs:
    rnorm(2) |> Cache(cachePath = tmpdir1, cacheId = "422bae4ed2f770cc")

    ## cacheId passed to override automatic digesting; using 422bae4ed2f770cc

    ## Object to retrieve (fn: rnorm, 422bae4ed2f770cc.rds) ...

    ## Loaded! Cached result from previous rnorm call

    ## [1] 0.1836433
    ## attr(,".Cache")
    ## attr(,".Cache")$newCache
    ## [1] FALSE
    ##
    ## attr(,"tags")
    ## [1] "cacheId:422bae4ed2f770cc"
    ## attr(,"callInCache")
    ## [1] ""

## 1.4 Working with the Cache manually

Since the cache is simply a `DBI` data table (of an SQLite database by default). In addition, there are several helpers in the `reproducible` package, including `showCache`, `keepCache` and `clearCache` that may be useful. Also, one can access cached items manually (rather than simply rerunning the same `Cache` function again).

    # As of reproducible version 1.0, there is a new backend directly using DBI
    mapHash <- unique(showCache(tmpDir, userTags = "project")$cacheId)

    ## Cache size:

    ## Total (including Rasters): 676 bytes

    ## Selected objects (not including Rasters): 676 bytes

    map <- loadFromCache(mapHash[1], cachePath = tmpDir)

    ## Loaded! Cached result from previous  call

    terra::plot(map)

    ## cleanup
    unlink(dirname(tmpDir), recursive = TRUE)

# 2 Alternative database backends

By default, caching relies on a sqlite database for it’s backend. While this works in many situations, there are some important limitations of using sqlite for caching, including 1) speed; 2) concurrent transactions; 3) sharing database across machines or projects. Fortunately, `Cache` makes use of `DBI` package and thus supports several database backends, including mysql and postgresql.

See https://github.com/PredictiveEcology/SpaDES/wiki/Using-alternate-database-backends-for-Cache for further information on configuring these additional backends.

# 3 Reproducible workflow

In general, we feel that a liberal use of `Cache` will make a re-usable and reproducible work flow. `shiny` apps can be made, taking advantage of `Cache`. Indeed, much of the difficulty in managing data sets and saving them for future use, can be accommodated by caching.