Write chain of DafReaders with a final DafWriter.

Produced by chain_writer(). Reads fall through in reverse order (writer last-wins); writes go to the final writer; deletes succeed only if the entry does not exist in any earlier daf.

Usage

WriteChainDaf(
  name = character(0),
  internal = new.env(parent = emptyenv()),
  cache = new.env(parent = emptyenv()),
  axis_version_counter = new.env(parent = emptyenv()),
  vector_version_counter = new.env(parent = emptyenv()),
  matrix_version_counter = new.env(parent = emptyenv()),
  dafs = list(),
  writer = DafWriter()
)

Arguments

name

Human-readable identifier for the Daf store.

internal

Internal per-store environment used by format backends to stash backend-specific state; reserved for package use.

cache

Three-tier cache environment (mapped / memory / query). See new_cache_env().

axis_version_counter

Environment tracking per-axis mutation counters; invalidates cached reads when an axis is modified.

vector_version_counter

Environment tracking per-vector mutation counters.

matrix_version_counter

Environment tracking per-matrix mutation counters.

dafs

Ordered list of base DafReaders.

writer

The final DafWriter (== dafs[[length(dafs)]]).

Examples

base <- memory_daf(name = "base")
writer <- memory_daf(name = "writer")
ch <- chain_writer(list(base, writer))
inherits(ch, "dafr::WriteChainDaf")
#> [1] TRUE