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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2022/08/03 21:56:18 UTC
[GitHub] [arrow-rs] alamb commented on a diff in pull request #1855: support compression for IPC
alamb commented on code in PR #1855:
URL: https://github.com/apache/arrow-rs/pull/1855#discussion_r937170314
##########
arrow/src/ipc/reader.rs:
##########
@@ -32,15 +32,78 @@ use crate::error::{ArrowError, Result};
use crate::ipc;
use crate::record_batch::{RecordBatch, RecordBatchOptions, RecordBatchReader};
+use crate::ipc::compression::ipc_compression::CompressionCodecType;
+use crate::ipc::compression::{
+ LENGTH_EMPTY_COMPRESSED_DATA, LENGTH_NO_COMPRESSED_DATA, LENGTH_OF_PREFIX_DATA,
+};
+use crate::ipc::CompressionType;
use ipc::CONTINUATION_MARKER;
use DataType::*;
/// Read a buffer based on offset and length
-fn read_buffer(buf: &ipc::Buffer, a_data: &[u8]) -> Buffer {
+/// From <https://github.com/apache/arrow/blob/6a936c4ff5007045e86f65f1a6b6c3c955ad5103/format/Message.fbs#L58>
+/// Each constituent buffer is first compressed with the indicated
+/// compressor, and then written with the uncompressed length in the first 8
+/// bytes as a 64-bit little-endian signed integer followed by the compressed
+/// buffer bytes (and then padding as required by the protocol). The
+/// uncompressed length may be set to -1 to indicate that the data that
+/// follows is not compressed, which can be useful for cases where
+/// compression does not yield appreciable savings.
+fn read_buffer(
+ buf: &ipc::Buffer,
+ a_data: &[u8],
+ compression_codec: &Option<CompressionCodecType>,
+) -> Buffer {
let start_offset = buf.offset() as usize;
let end_offset = start_offset + buf.length() as usize;
let buf_data = &a_data[start_offset..end_offset];
- Buffer::from(&buf_data)
+ // corner case: empty buffer
+ if buf_data.is_empty() {
+ return Buffer::from(buf_data);
+ }
+ match compression_codec {
+ Some(_decompressor) if cfg!(feature = "ipc_compression") || cfg!(test) => {
+ // 8byte + data
+ // read the first 8 bytes
+ // if the data is compressed, decompress the data, otherwise return as is
+ let decompressed_length = read_uncompressed_size(buf_data);
+ if decompressed_length == LENGTH_EMPTY_COMPRESSED_DATA {
+ // emtpy
+ let empty = Vec::<u8>::new();
+ Buffer::from(empty)
+ } else if decompressed_length == LENGTH_NO_COMPRESSED_DATA {
+ // not compress
+ let data = &buf_data[(LENGTH_OF_PREFIX_DATA as usize)..];
+ Buffer::from(data)
+ } else {
+ // decompress data using the codec
+ let mut _uncompressed_buffer =
+ Vec::with_capacity(decompressed_length as usize);
+ let _input_data = &buf_data[(LENGTH_OF_PREFIX_DATA as usize)..];
Review Comment:
Something still isn't quite right with this code -- instead of gating the code on the `test` feature, I think the more typical pattern is to gate the entire test on the `ipc_compression` feature
So something like
```rust
#[cfg(ipc_compression)]
#[test]
fn read_generated_streams_200() {
let testdata = crate::util::test_util::arrow_test_data();
let version = "2.0.0-compression";
...
}
```
##########
arrow/Cargo.toml:
##########
@@ -83,6 +86,8 @@ rand = { version = "0.8", default-features = false, features = ["std", "std_rng
criterion = { version = "0.3", default-features = false }
flate2 = { version = "1", default-features = false, features = ["rust_backend"] }
tempfile = { version = "3", default-features = false }
+lz4 = { version = "1.23", default-features = false }
+zstd = { version = "0.11", default-features = false }
Review Comment:
I don't think these need to be in dev dependencies do they? If they are already in the dependencies of the crate?
##########
arrow/src/ipc/reader.rs:
##########
@@ -32,15 +32,78 @@ use crate::error::{ArrowError, Result};
use crate::ipc;
use crate::record_batch::{RecordBatch, RecordBatchOptions, RecordBatchReader};
+use crate::ipc::compression::ipc_compression::CompressionCodecType;
+use crate::ipc::compression::{
+ LENGTH_EMPTY_COMPRESSED_DATA, LENGTH_NO_COMPRESSED_DATA, LENGTH_OF_PREFIX_DATA,
+};
+use crate::ipc::CompressionType;
use ipc::CONTINUATION_MARKER;
use DataType::*;
/// Read a buffer based on offset and length
-fn read_buffer(buf: &ipc::Buffer, a_data: &[u8]) -> Buffer {
+/// From <https://github.com/apache/arrow/blob/6a936c4ff5007045e86f65f1a6b6c3c955ad5103/format/Message.fbs#L58>
+/// Each constituent buffer is first compressed with the indicated
+/// compressor, and then written with the uncompressed length in the first 8
+/// bytes as a 64-bit little-endian signed integer followed by the compressed
+/// buffer bytes (and then padding as required by the protocol). The
+/// uncompressed length may be set to -1 to indicate that the data that
+/// follows is not compressed, which can be useful for cases where
+/// compression does not yield appreciable savings.
+fn read_buffer(
+ buf: &ipc::Buffer,
+ a_data: &[u8],
+ compression_codec: &CompressionCodecType,
+) -> Buffer {
let start_offset = buf.offset() as usize;
let end_offset = start_offset + buf.length() as usize;
let buf_data = &a_data[start_offset..end_offset];
- Buffer::from(&buf_data)
+ // corner case: empty buffer
+ if buf_data.is_empty() {
+ return Buffer::from(buf_data);
+ }
+ match compression_codec {
+ CompressionCodecType::Lz4Frame | CompressionCodecType::Zstd
+ if cfg!(feature = "ipc_compression") || cfg!(test) =>
+ {
+ // 8byte + data
+ // read the first 8 bytes
+ // if the data is compressed, decompress the data, otherwise return as is
+ let decompressed_length = read_uncompressed_size(buf_data);
+ if decompressed_length == LENGTH_EMPTY_COMPRESSED_DATA {
+ // emtpy
+ let empty = Vec::<u8>::new();
+ Buffer::from(empty)
+ } else if decompressed_length == LENGTH_NO_COMPRESSED_DATA {
+ // not compress
+ let data = &buf_data[(LENGTH_OF_PREFIX_DATA as usize)..];
+ Buffer::from(data)
+ } else {
+ // decompress data using the codec
+ let mut _uncompressed_buffer = Vec::new();
+ let _input_data = &buf_data[(LENGTH_OF_PREFIX_DATA as usize)..];
+ #[cfg(any(feature = "ipc_compression", test))]
+ compression_codec
+ .decompress(_input_data, &mut _uncompressed_buffer)
+ .unwrap();
+ Buffer::from(_uncompressed_buffer)
+ }
+ }
+ CompressionCodecType::NoCompression => Buffer::from(buf_data),
+ _ => {
Review Comment:
I think returning an error is the correct way but as you have identifed above you can't do that without changing the signature to `Result<Buffer>` -- but since decompression can fail we probably need to make the change
##########
arrow/src/ipc/reader.rs:
##########
@@ -32,15 +32,78 @@ use crate::error::{ArrowError, Result};
use crate::ipc;
use crate::record_batch::{RecordBatch, RecordBatchOptions, RecordBatchReader};
+use crate::ipc::compression::ipc_compression::CompressionCodecType;
+use crate::ipc::compression::{
+ LENGTH_EMPTY_COMPRESSED_DATA, LENGTH_NO_COMPRESSED_DATA, LENGTH_OF_PREFIX_DATA,
+};
+use crate::ipc::CompressionType;
use ipc::CONTINUATION_MARKER;
use DataType::*;
/// Read a buffer based on offset and length
-fn read_buffer(buf: &ipc::Buffer, a_data: &[u8]) -> Buffer {
+/// From <https://github.com/apache/arrow/blob/6a936c4ff5007045e86f65f1a6b6c3c955ad5103/format/Message.fbs#L58>
+/// Each constituent buffer is first compressed with the indicated
+/// compressor, and then written with the uncompressed length in the first 8
+/// bytes as a 64-bit little-endian signed integer followed by the compressed
+/// buffer bytes (and then padding as required by the protocol). The
+/// uncompressed length may be set to -1 to indicate that the data that
+/// follows is not compressed, which can be useful for cases where
+/// compression does not yield appreciable savings.
+fn read_buffer(
Review Comment:
do you still intend to make this change? Or is it planned for a subsequent PR?
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