/
definition_levels.rs
436 lines (378 loc) · 13.7 KB
/
definition_levels.rs
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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
use std::ops::Range;
use arrow::array::BooleanBufferBuilder;
use arrow::bitmap::Bitmap;
use arrow::buffer::Buffer;
use crate::arrow::buffer::bit_util::count_set_bits;
use crate::arrow::record_reader::buffer::BufferQueue;
use crate::basic::Encoding;
use crate::column::reader::decoder::{
ColumnLevelDecoder, ColumnLevelDecoderImpl, DefinitionLevelDecoder, LevelsBufferSlice,
};
use crate::errors::{ParquetError, Result};
use crate::schema::types::ColumnDescPtr;
use crate::util::memory::ByteBufferPtr;
use super::{buffer::ScalarBuffer, MIN_BATCH_SIZE};
enum BufferInner {
/// Compute levels and null mask
Full {
levels: ScalarBuffer<i16>,
nulls: BooleanBufferBuilder,
max_level: i16,
},
/// Only compute null bitmask - requires max level to be 1
///
/// This is an optimisation for the common case of a nullable scalar column, as decoding
/// the definition level data is only required when decoding nested structures
///
Mask { nulls: BooleanBufferBuilder },
}
pub struct DefinitionLevelBuffer {
inner: BufferInner,
/// The length of this buffer
///
/// Note: `buffer` and `builder` may contain more elements
len: usize,
}
impl DefinitionLevelBuffer {
pub fn new(desc: &ColumnDescPtr, null_mask_only: bool) -> Self {
let inner = match null_mask_only {
true => {
assert_eq!(
desc.max_def_level(),
1,
"max definition level must be 1 to only compute null bitmask"
);
assert_eq!(
desc.max_rep_level(),
0,
"max repetition level must be 0 to only compute null bitmask"
);
BufferInner::Mask {
nulls: BooleanBufferBuilder::new(0),
}
}
false => BufferInner::Full {
levels: ScalarBuffer::new(),
nulls: BooleanBufferBuilder::new(0),
max_level: desc.max_def_level(),
},
};
Self { inner, len: 0 }
}
pub fn split_levels(&mut self, len: usize) -> Option<Buffer> {
match &mut self.inner {
BufferInner::Full { levels, .. } => {
let out = levels.split_off(len);
self.len = levels.len();
Some(out)
}
BufferInner::Mask { .. } => None,
}
}
pub fn set_len(&mut self, len: usize) {
assert_eq!(self.nulls().len(), len);
self.len = len;
}
/// Split `len` levels out of `self`
pub fn split_bitmask(&mut self, len: usize) -> Bitmap {
let old_builder = match &mut self.inner {
BufferInner::Full { nulls, .. } => nulls,
BufferInner::Mask { nulls } => nulls,
};
// Compute the number of values left behind
let num_left_values = old_builder.len() - len;
let mut new_builder =
BooleanBufferBuilder::new(MIN_BATCH_SIZE.max(num_left_values));
// Copy across remaining values
new_builder.append_packed_range(len..old_builder.len(), old_builder.as_slice());
// Truncate buffer
old_builder.resize(len);
// Swap into self
self.len = new_builder.len();
Bitmap::from(std::mem::replace(old_builder, new_builder).finish())
}
pub fn nulls(&self) -> &BooleanBufferBuilder {
match &self.inner {
BufferInner::Full { nulls, .. } => nulls,
BufferInner::Mask { nulls } => nulls,
}
}
}
impl LevelsBufferSlice for DefinitionLevelBuffer {
fn capacity(&self) -> usize {
usize::MAX
}
fn count_nulls(&self, range: Range<usize>, _max_level: i16) -> usize {
let total_count = range.end - range.start;
let range = range.start + self.len..range.end + self.len;
total_count - count_set_bits(self.nulls().as_slice(), range)
}
}
enum MaybePacked {
Packed(PackedDecoder),
Fallback(ColumnLevelDecoderImpl),
}
impl MaybePacked {
#[inline]
fn packed(&mut self) -> &mut PackedDecoder {
match self {
Self::Packed(d) => d,
_ => panic!("expected packed"),
}
}
#[inline]
fn fallback(&mut self) -> &mut ColumnLevelDecoderImpl {
match self {
Self::Fallback(d) => d,
_ => panic!("expected packed"),
}
}
}
pub struct DefinitionLevelBufferDecoder {
max_level: i16,
decoder: MaybePacked,
}
impl DefinitionLevelBufferDecoder {
pub fn new(max_level: i16, packed: bool) -> Self {
let decoder = match packed {
true => MaybePacked::Packed(PackedDecoder::new()),
false => MaybePacked::Fallback(ColumnLevelDecoderImpl::new(max_level)),
};
Self { max_level, decoder }
}
}
impl ColumnLevelDecoder for DefinitionLevelBufferDecoder {
type Slice = DefinitionLevelBuffer;
fn set_data(&mut self, encoding: Encoding, data: ByteBufferPtr) {
match &mut self.decoder {
MaybePacked::Packed(d) => d.set_data(encoding, data),
MaybePacked::Fallback(d) => d.set_data(encoding, data),
}
}
fn read(&mut self, writer: &mut Self::Slice, range: Range<usize>) -> Result<usize> {
match &mut writer.inner {
BufferInner::Full {
levels,
nulls,
max_level,
} => {
assert_eq!(self.max_level, *max_level);
assert_eq!(range.start + writer.len, nulls.len());
let decoder = self.decoder.fallback();
levels.resize(range.end + writer.len);
let slice = &mut levels.as_slice_mut()[writer.len..];
let levels_read = decoder.read(slice, range.clone())?;
nulls.reserve(levels_read);
for i in &slice[range.start..range.start + levels_read] {
nulls.append(i == max_level)
}
Ok(levels_read)
}
BufferInner::Mask { nulls } => {
assert_eq!(self.max_level, 1);
assert_eq!(range.start + writer.len, nulls.len());
let decoder = self.decoder.packed();
decoder.read(nulls, range.end - range.start)
}
}
}
}
impl DefinitionLevelDecoder for DefinitionLevelBufferDecoder {
fn skip_def_levels(
&mut self,
_num_levels: usize,
_max_def_level: i16,
) -> Result<(usize, usize)> {
Err(nyi_err!("https://github.com/apache/arrow-rs/issues/1792"))
}
}
/// An optimized decoder for decoding [RLE] and [BIT_PACKED] data with a bit width of 1
/// directly into a bitmask
///
/// This is significantly faster than decoding the data into `[i16]` and then computing
/// a bitmask from this, as not only can it skip this buffer allocation and construction,
/// but it can exploit properties of the encoded data to reduce work further
///
/// In particular:
///
/// * Packed runs are already bitmask encoded and can simply be appended
/// * Runs of 1 or 0 bits can be efficiently appended with byte (or larger) operations
///
/// [RLE]: https://github.com/apache/parquet-format/blob/master/Encodings.md#run-length-encoding--bit-packing-hybrid-rle--3
/// [BIT_PACKED]: https://github.com/apache/parquet-format/blob/master/Encodings.md#bit-packed-deprecated-bit_packed--4
struct PackedDecoder {
data: ByteBufferPtr,
data_offset: usize,
rle_left: usize,
rle_value: bool,
packed_count: usize,
packed_offset: usize,
}
impl PackedDecoder {
fn next_rle_block(&mut self) -> Result<()> {
let indicator_value = self.decode_header()?;
if indicator_value & 1 == 1 {
let len = (indicator_value >> 1) as usize;
self.packed_count = len * 8;
self.packed_offset = 0;
} else {
self.rle_left = (indicator_value >> 1) as usize;
let byte = *self.data.as_ref().get(self.data_offset).ok_or_else(|| {
ParquetError::EOF(
"unexpected end of file whilst decoding definition levels rle value"
.into(),
)
})?;
self.data_offset += 1;
self.rle_value = byte != 0;
}
Ok(())
}
/// Decodes a VLQ encoded little endian integer and returns it
fn decode_header(&mut self) -> Result<i64> {
let mut offset = 0;
let mut v: i64 = 0;
while offset < 10 {
let byte = *self
.data
.as_ref()
.get(self.data_offset + offset)
.ok_or_else(|| {
ParquetError::EOF(
"unexpected end of file whilst decoding definition levels rle header"
.into(),
)
})?;
v |= ((byte & 0x7F) as i64) << (offset * 7);
offset += 1;
if byte & 0x80 == 0 {
self.data_offset += offset;
return Ok(v);
}
}
Err(general_err!("too many bytes for VLQ"))
}
}
impl PackedDecoder {
fn new() -> Self {
Self {
data: ByteBufferPtr::new(vec![]),
data_offset: 0,
rle_left: 0,
rle_value: false,
packed_count: 0,
packed_offset: 0,
}
}
fn set_data(&mut self, encoding: Encoding, data: ByteBufferPtr) {
self.rle_left = 0;
self.rle_value = false;
self.packed_offset = 0;
self.packed_count = match encoding {
Encoding::RLE => 0,
Encoding::BIT_PACKED => data.len() * 8,
_ => unreachable!("invalid level encoding: {}", encoding),
};
self.data = data;
self.data_offset = 0;
}
fn read(&mut self, buffer: &mut BooleanBufferBuilder, len: usize) -> Result<usize> {
let mut read = 0;
while read != len {
if self.rle_left != 0 {
let to_read = self.rle_left.min(len - read);
buffer.append_n(to_read, self.rle_value);
self.rle_left -= to_read;
read += to_read;
} else if self.packed_count != self.packed_offset {
let to_read = (self.packed_count - self.packed_offset).min(len - read);
let offset = self.data_offset * 8 + self.packed_offset;
buffer.append_packed_range(offset..offset + to_read, self.data.as_ref());
self.packed_offset += to_read;
read += to_read;
if self.packed_offset == self.packed_count {
self.data_offset += self.packed_count / 8;
}
} else if self.data_offset == self.data.len() {
break;
} else {
self.next_rle_block()?
}
}
Ok(read)
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::sync::Arc;
use crate::basic::Type as PhysicalType;
use crate::encodings::rle::RleEncoder;
use crate::schema::types::{ColumnDescriptor, ColumnPath, Type};
use rand::{thread_rng, Rng};
#[test]
fn test_packed_decoder() {
let mut rng = thread_rng();
let len: usize = rng.gen_range(512..1024);
let mut expected = BooleanBufferBuilder::new(len);
let mut encoder = RleEncoder::new(1, 1024);
for _ in 0..len {
let bool = rng.gen_bool(0.8);
assert!(encoder.put(bool as u64).unwrap());
expected.append(bool);
}
assert_eq!(expected.len(), len);
let encoded = encoder.consume().unwrap();
let mut decoder = PackedDecoder::new();
decoder.set_data(Encoding::RLE, ByteBufferPtr::new(encoded));
// Decode data in random length intervals
let mut decoded = BooleanBufferBuilder::new(len);
loop {
let remaining = len - decoded.len();
if remaining == 0 {
break;
}
let to_read = rng.gen_range(1..=remaining);
decoder.read(&mut decoded, to_read).unwrap();
}
assert_eq!(decoded.len(), len);
assert_eq!(decoded.as_slice(), expected.as_slice());
}
#[test]
fn test_split_off() {
let t = Type::primitive_type_builder("col", PhysicalType::INT32)
.build()
.unwrap();
let descriptor = Arc::new(ColumnDescriptor::new(
Arc::new(t),
1,
0,
ColumnPath::new(vec![]),
));
let mut buffer = DefinitionLevelBuffer::new(&descriptor, true);
match &mut buffer.inner {
BufferInner::Mask { nulls } => nulls.append_n(100, false),
_ => unreachable!(),
};
let bitmap = buffer.split_bitmask(19);
// Should have split off 19 records leaving, 81 behind
assert_eq!(bitmap.bit_len(), 3 * 8); // Note: bitmask only tracks bytes not bits
assert_eq!(buffer.nulls().len(), 81);
}
}