arrow

Pure-Elixir Apache Arrow. Verified round-trip against the upstream arrow-testing cross-language fixture corpus, with pyarrow-produced golden files in the default test suite.

Install

{:arrow, "~> 0.1.0"}

:flatbuf is a :dev-only dependency (tracking lawik/flatbuf main) — used once to regenerate the metadata codec from the vendored .fbs sources. Generated code is dependency-free. After regenerating, re-apply @moduledoc false to the generated modules (they are internal and kept out of the docs):

perl -i -pe 's{^(\s*)\@moduledoc ".*"$}{$1\@moduledoc false}' lib/arrow/ipc/flatbuf/*.ex

Use

In-memory data model:

schema = %Arrow.Schema{
  fields: [
    %Arrow.Field{name: "n", type: %Arrow.Type.Int{bit_width: 32, signed: true}, nullable: false},
    %Arrow.Field{name: "s", type: %Arrow.Type.Utf8{}, nullable: true}
  ]
}

batch = %Arrow.RecordBatch{
  schema: schema,
  length: 3,
  columns: [
    %Arrow.Array.Int32{length: 3, null_count: 0, values: Arrow.Buffer.pack_primitive([1, 2, 3], :int32)},
    %Arrow.Array.Utf8{length: 3, null_count: 0,
                      offsets: Arrow.Buffer.pack_int32_offsets([3, 3, 3]),
                      values: "foobarbaz"}
  ]
}

IPC stream + file formats:

bin = Arrow.Ipc.Stream.encode(schema, [batch])
{:ok, %{schema: ^schema, dictionaries: %{}, batches: [_]}} = Arrow.Ipc.Stream.decode(bin)

bin = Arrow.Ipc.File.encode(schema, [batch])
{:ok, decoded} = Arrow.Ipc.File.decode(bin)

Decoders return {:ok, payload} or {:error, %Arrow.DecodeError{kind: :unsupported | :malformed}}; decode!/1 variants raise instead.

Arrow integration test JSON:

{:ok, %{schema: _, dictionaries: _, batches: _}} = Arrow.Json.decode(File.read!("fixture.json"))
iodata = Arrow.Json.encode(schema, [batch])

Null-aware logical equality across formats and producers:

Arrow.Logical.payloads_equivalent?(from_stream, from_json)

Mix tasks for poking at IPC data from the command line:

mix arrow.inspect data.arrow             # schema, batch row counts, dictionaries
mix arrow.convert data.arrow out.stream  # file ↔ stream, input auto-detected

Archery integration CLI (subprocess shims under bin/, forwarding to repo-only scripts under scripts/ — not part of the Hex package):

mix run scripts/json_to_arrow.exs --json fixture.json --arrow out.arrow
mix run scripts/arrow_to_json.exs --arrow file.arrow --json out.json
mix run scripts/validate.exs --json fixture.json --arrow file.arrow

Run the tests:

mix test                          # always-run suite, incl. golden decode
                                  # tests against pyarrow-produced IPC
                                  # files (test/golden/)
./scripts/fetch_fixtures.sh       # one-time: clone apache/arrow-testing
mix test --include fixtures       # cross-language conformance suite

Coverage

Logical types: Null, Bool, Int{8,16,32,64} (signed + unsigned), Float{32,64}, Utf8, Binary, Date{32,64}, Timestamp (all units

• timezone), Time{32,64}, Duration, FixedSizeBinary, FixedSizeList, List, Struct, Map, Decimal{32,64,128,256}, Dictionary (incl. DictionaryBatch in IPC), Interval (YEAR_MONTH / DAY_TIME / MONTH_DAY_NANO), LargeUtf8, LargeBinary, LargeList.

IPC: stream framing, file format (magic + Footer + Block descriptors), RecordBatch + DictionaryBatch messages, end-of-stream markers.

Limitations

• Little-endian only. Big-endian IPC payloads are rejected on decode.
• IPC body compression (LZ4_FRAME / ZSTD) is rejected on decode.
• Union (sparse + dense), BinaryView / Utf8View, ListView / LargeListView, RunEndEncoded, and Float16 are rejected on decode and absent from the data model.
• Legacy (pre-0.15 / V4, no continuation marker) IPC files are rejected.
• Tensor and SparseTensor messages are out of scope for the IPC reader.
• Delta DictionaryBatch messages are rejected.
• force_align and (vector64) follow flatbuf's coverage, not ours.
• Float32 / Float64NaN slots break the logical comparator (NaN != NaN per IEEE-754). Float NaN-heavy data needs custom comparison.

License

Apache-2.0. This project is REUSE-compliant: every file carries SPDX licensing information (in-file headers or REUSE.toml), license texts live in LICENSES/, and NOTICE carries the attribution for the FlatBuffers schemas vendored from apache/arrow. reuse spdx generates an SPDX bill of materials. Not affiliated with the Apache Software Foundation.