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encoding.rs
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encoding.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.
//! Contains all supported encoders for Parquet.
use std::{cmp, io::Write, marker::PhantomData, mem, slice};
use crate::internal::{
basic::*, data_type::*, encodings::rle::RleEncoder, errors::{ParquetError, Result}, schema::types::ColumnDescPtr, util::{
bit_util::{self, log2, num_required_bits, BitWriter}, hash_util, memory::{Buffer, ByteBuffer, ByteBufferPtr, MemTrackerPtr}
}
};
// ----------------------------------------------------------------------
// Encoders
/// An Parquet encoder for the data type `T`.
///
/// Currently this allocates internal buffers for the encoded values. After done putting
/// values, caller should call `flush_buffer()` to get an immutable buffer pointer.
pub trait Encoder<T: DataType> {
/// Encodes data from `values`.
fn put(&mut self, values: &[T::Type]) -> Result<()>;
/// Encodes data from `values`, which contains spaces for null values, that is
/// identified by `valid_bits`.
///
/// Returns the number of non-null values encoded.
fn put_spaced(&mut self, values: &[T::Type], valid_bits: &[u8]) -> Result<usize> {
let num_values = values.len();
let mut buffer = Vec::with_capacity(num_values);
// TODO: this is pretty inefficient. Revisit in future.
for i in 0..num_values {
if bit_util::get_bit(valid_bits, i) {
buffer.push(values[i].clone());
}
}
self.put(&buffer[..])?;
Ok(buffer.len())
}
/// Returns the encoding type of this encoder.
fn encoding(&self) -> Encoding;
/// Returns an estimate of the encoded data, in bytes.
/// Method call must be O(1).
fn estimated_data_encoded_size(&self) -> usize;
/// Flushes the underlying byte buffer that's being processed by this encoder, and
/// return the immutable copy of it. This will also reset the internal state.
fn flush_buffer(&mut self) -> Result<ByteBufferPtr>;
}
/// Gets a encoder for the particular data type `T` and encoding `encoding`. Memory usage
/// for the encoder instance is tracked by `mem_tracker`.
pub fn get_encoder<T: DataType>(
desc: ColumnDescPtr, encoding: Encoding, mem_tracker: MemTrackerPtr,
) -> Result<Box<dyn Encoder<T>>> {
let encoder: Box<dyn Encoder<T>> = match encoding {
Encoding::Plain => Box::new(PlainEncoder::new(desc, mem_tracker, vec![])),
Encoding::RleDictionary | Encoding::PlainDictionary => {
return Err(general_err!(
"Cannot initialize this encoding through this function"
));
}
Encoding::Rle => Box::new(RleValueEncoder::new()),
Encoding::DeltaBinaryPacked => Box::new(DeltaBitPackEncoder::new()),
Encoding::DeltaLengthByteArray => Box::new(DeltaLengthByteArrayEncoder::new()),
Encoding::DeltaByteArray => Box::new(DeltaByteArrayEncoder::new()),
e => return Err(nyi_err!("Encoding {} is not supported", e)),
};
Ok(encoder)
}
// ----------------------------------------------------------------------
// Plain encoding
/// Plain encoding that supports all types.
/// Values are encoded back to back.
/// The plain encoding is used whenever a more efficient encoding can not be used.
/// It stores the data in the following format:
/// - BOOLEAN - 1 bit per value, 0 is false; 1 is true.
/// - INT32 - 4 bytes per value, stored as little-endian.
/// - INT64 - 8 bytes per value, stored as little-endian.
/// - FLOAT - 4 bytes per value, stored as IEEE little-endian.
/// - DOUBLE - 8 bytes per value, stored as IEEE little-endian.
/// - BYTE_ARRAY - 4 byte length stored as little endian, followed by bytes.
/// - FIXED_LEN_BYTE_ARRAY - just the bytes are stored.
pub struct PlainEncoder<T: DataType> {
buffer: ByteBuffer,
bit_writer: BitWriter,
desc: ColumnDescPtr,
_phantom: PhantomData<T>,
}
impl<T: DataType> PlainEncoder<T> {
/// Creates new plain encoder.
pub fn new(desc: ColumnDescPtr, mem_tracker: MemTrackerPtr, vec: Vec<u8>) -> Self {
let mut byte_buffer = ByteBuffer::new().with_mem_tracker(mem_tracker);
byte_buffer.set_data(vec);
Self {
buffer: byte_buffer,
bit_writer: BitWriter::new(256),
desc,
_phantom: PhantomData,
}
}
}
impl<T: DataType> Encoder<T> for PlainEncoder<T> {
default fn put(&mut self, values: &[T::Type]) -> Result<()> {
let bytes = unsafe {
slice::from_raw_parts(
values as *const [T::Type] as *const u8,
mem::size_of::<T::Type>() * values.len(),
)
};
self.buffer.write_all(bytes)?;
Ok(())
}
fn encoding(&self) -> Encoding {
Encoding::Plain
}
fn estimated_data_encoded_size(&self) -> usize {
self.buffer.size() + self.bit_writer.bytes_written()
}
#[inline]
default fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
self.buffer.write_all(self.bit_writer.flush_buffer())?;
self.buffer.flush()?;
self.bit_writer.clear();
Ok(self.buffer.consume())
}
}
impl Encoder<BoolType> for PlainEncoder<BoolType> {
fn put(&mut self, values: &[bool]) -> Result<()> {
for v in values {
self.bit_writer.put_value(*v as u64, 1)?;
}
Ok(())
}
}
impl Encoder<Int96Type> for PlainEncoder<Int96Type> {
fn put(&mut self, values: &[Int96]) -> Result<()> {
for v in values {
self.buffer.write_all(v.as_bytes())?;
}
self.buffer.flush()?;
Ok(())
}
}
impl Encoder<ByteArrayType> for PlainEncoder<ByteArrayType> {
fn put(&mut self, values: &[ByteArray]) -> Result<()> {
for v in values {
self.buffer
.write_all(&(v.len().to_le() as u32).as_bytes())?;
self.buffer.write_all(v.data())?;
}
self.buffer.flush()?;
Ok(())
}
}
impl Encoder<FixedLenByteArrayType> for PlainEncoder<FixedLenByteArrayType> {
fn put(&mut self, values: &[ByteArray]) -> Result<()> {
for v in values {
self.buffer.write_all(v.data())?;
}
self.buffer.flush()?;
Ok(())
}
}
// ----------------------------------------------------------------------
// Dictionary encoding
const INITIAL_HASH_TABLE_SIZE: usize = 1024;
const MAX_HASH_LOAD: f32 = 0.7;
const HASH_SLOT_EMPTY: i32 = -1;
/// Dictionary encoder.
/// The dictionary encoding builds a dictionary of values encountered in a given column.
/// The dictionary page is written first, before the data pages of the column chunk.
///
/// Dictionary page format: the entries in the dictionary - in dictionary order -
/// using the plain encoding.
///
/// Data page format: the bit width used to encode the entry ids stored as 1 byte
/// (max bit width = 32), followed by the values encoded using RLE/Bit packed described
/// above (with the given bit width).
pub struct DictEncoder<T: DataType> {
// Descriptor for the column to be encoded.
desc: ColumnDescPtr,
// Size of the table. **Must be** a power of 2.
hash_table_size: usize,
// Store `hash_table_size` - 1, so that `j & mod_bitmask` is equivalent to
// `j % hash_table_size`, but uses far fewer CPU cycles.
mod_bitmask: u32,
// Stores indices which map (many-to-one) to the values in the `uniques` array.
// Here we are using fix-sized array with linear probing.
// A slot with `HASH_SLOT_EMPTY` indicates the slot is not currently occupied.
hash_slots: Buffer<i32>,
// Indices that have not yet be written out by `write_indices()`.
buffered_indices: Buffer<i32>,
// The unique observed values.
uniques: Buffer<T::Type>,
// Size in bytes needed to encode this dictionary.
uniques_size_in_bytes: usize,
// Tracking memory usage for the various data structures in this struct.
mem_tracker: MemTrackerPtr,
}
impl<T: DataType> DictEncoder<T> {
/// Creates new dictionary encoder.
pub fn new(desc: ColumnDescPtr, mem_tracker: MemTrackerPtr) -> Self {
let mut slots = Buffer::new().with_mem_tracker(mem_tracker.clone());
slots.resize(INITIAL_HASH_TABLE_SIZE, -1);
Self {
desc,
hash_table_size: INITIAL_HASH_TABLE_SIZE,
mod_bitmask: (INITIAL_HASH_TABLE_SIZE - 1) as u32,
hash_slots: slots,
buffered_indices: Buffer::new().with_mem_tracker(mem_tracker.clone()),
uniques: Buffer::new().with_mem_tracker(mem_tracker.clone()),
uniques_size_in_bytes: 0,
mem_tracker,
}
}
/// Returns true if dictionary entries are sorted, false otherwise.
#[inline]
pub fn is_sorted(&self) -> bool {
// Sorting is not supported currently.
false
}
/// Returns number of unique values (keys) in the dictionary.
pub fn num_entries(&self) -> usize {
self.uniques.size()
}
/// Returns size of unique values (keys) in the dictionary, in bytes.
pub fn dict_encoded_size(&self) -> usize {
self.uniques_size_in_bytes
}
/// Writes out the dictionary values with PLAIN encoding in a byte buffer, and return
/// the result.
#[inline]
pub fn write_dict(&self) -> Result<ByteBufferPtr> {
let mut plain_encoder =
PlainEncoder::<T>::new(self.desc.clone(), self.mem_tracker.clone(), vec![]);
plain_encoder.put(self.uniques.data())?;
plain_encoder.flush_buffer()
}
/// Writes out the dictionary values with RLE encoding in a byte buffer, and return
/// the result.
#[inline]
pub fn write_indices(&mut self) -> Result<ByteBufferPtr> {
// TODO: the caller should allocate the buffer
let buffer_len = self.estimated_data_encoded_size();
let mut buffer: Vec<u8> = vec![0; buffer_len as usize];
buffer[0] = self.bit_width() as u8;
self.mem_tracker.alloc(buffer.capacity() as i64);
// Write bit width in the first byte
buffer.write_all((self.bit_width() as u8).as_bytes())?;
let mut encoder = RleEncoder::new_from_buf(self.bit_width(), buffer, 1);
for index in self.buffered_indices.data() {
if !encoder.put(*index as u64)? {
return Err(general_err!("Encoder doesn't have enough space"));
}
}
self.buffered_indices.clear();
Ok(ByteBufferPtr::new(encoder.consume()?))
}
#[inline]
fn put_one(&mut self, value: &T::Type) -> Result<()> {
let mut j = (hash_util::hash(value, 0) & self.mod_bitmask) as usize;
let mut index = self.hash_slots[j];
while index != HASH_SLOT_EMPTY && self.uniques[index as usize] != *value {
j += 1;
if j == self.hash_table_size {
j = 0;
}
index = self.hash_slots[j];
}
if index == HASH_SLOT_EMPTY {
index = self.uniques.size() as i32;
self.hash_slots[j] = index;
self.add_dict_key(value.clone());
if self.uniques.size() > (self.hash_table_size as f32 * MAX_HASH_LOAD) as usize {
self.double_table_size();
}
}
self.buffered_indices.push(index);
Ok(())
}
#[inline]
fn add_dict_key(&mut self, value: T::Type) {
self.uniques_size_in_bytes += self.get_encoded_size(&value);
self.uniques.push(value);
}
#[inline]
fn bit_width(&self) -> u8 {
let num_entries = self.uniques.size();
if num_entries == 0 {
0
} else if num_entries == 1 {
1
} else {
log2(num_entries as u64) as u8
}
}
#[inline]
fn double_table_size(&mut self) {
let new_size = self.hash_table_size * 2;
let mut new_hash_slots = Buffer::new().with_mem_tracker(self.mem_tracker.clone());
new_hash_slots.resize(new_size, HASH_SLOT_EMPTY);
for i in 0..self.hash_table_size {
let index = self.hash_slots[i];
if index == HASH_SLOT_EMPTY {
continue;
}
let value = &self.uniques[index as usize];
let mut j = (hash_util::hash(value, 0) & ((new_size - 1) as u32)) as usize;
let mut slot = new_hash_slots[j];
while slot != HASH_SLOT_EMPTY && self.uniques[slot as usize] != *value {
j += 1;
if j == new_size {
j = 0;
}
slot = new_hash_slots[j];
}
new_hash_slots[j] = index;
}
self.hash_table_size = new_size;
self.mod_bitmask = (new_size - 1) as u32;
self.hash_slots = new_hash_slots;
}
}
impl<T: DataType> Encoder<T> for DictEncoder<T> {
#[inline]
fn put(&mut self, values: &[T::Type]) -> Result<()> {
for i in values {
self.put_one(&i)?
}
Ok(())
}
#[inline]
fn encoding(&self) -> Encoding {
Encoding::PlainDictionary
}
#[inline]
fn estimated_data_encoded_size(&self) -> usize {
let bit_width = self.bit_width();
1 + RleEncoder::min_buffer_size(bit_width)
+ RleEncoder::max_buffer_size(bit_width, self.buffered_indices.size())
}
#[inline]
fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
self.write_indices()
}
}
/// Provides encoded size for a data type.
/// This is a workaround to calculate dictionary size in bytes.
trait DictEncodedSize<T: DataType> {
fn get_encoded_size(&self, value: &T::Type) -> usize;
}
impl<T: DataType> DictEncodedSize<T> for DictEncoder<T> {
#[inline]
default fn get_encoded_size(&self, _: &T::Type) -> usize {
mem::size_of::<T::Type>()
}
}
impl DictEncodedSize<ByteArrayType> for DictEncoder<ByteArrayType> {
#[inline]
fn get_encoded_size(&self, value: &ByteArray) -> usize {
mem::size_of::<u32>() + value.len()
}
}
impl DictEncodedSize<FixedLenByteArrayType> for DictEncoder<FixedLenByteArrayType> {
#[inline]
fn get_encoded_size(&self, _value: &ByteArray) -> usize {
self.desc.type_length() as usize
}
}
// ----------------------------------------------------------------------
// RLE encoding
const DEFAULT_RLE_BUFFER_LEN: usize = 1024;
/// RLE/Bit-Packing hybrid encoding for values.
/// Currently is used only for data pages v2 and supports boolean types.
pub struct RleValueEncoder<T: DataType> {
// Buffer with raw values that we collect,
// when flushing buffer they are encoded using RLE encoder
encoder: Option<RleEncoder>,
_phantom: PhantomData<T>,
}
impl<T: DataType> RleValueEncoder<T> {
/// Creates new rle value encoder.
pub fn new() -> Self {
Self {
encoder: None,
_phantom: PhantomData,
}
}
}
impl<T: DataType> Encoder<T> for RleValueEncoder<T> {
#[inline]
default fn put(&mut self, _values: &[T::Type]) -> Result<()> {
panic!("RleValueEncoder only supports BoolType");
}
fn encoding(&self) -> Encoding {
Encoding::Rle
}
#[inline]
default fn estimated_data_encoded_size(&self) -> usize {
match self.encoder {
Some(ref enc) => enc.len(),
None => 0,
}
}
#[inline]
default fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
panic!("RleValueEncoder only supports BoolType");
}
}
impl Encoder<BoolType> for RleValueEncoder<BoolType> {
#[inline]
default fn put(&mut self, values: &[bool]) -> Result<()> {
if self.encoder.is_none() {
self.encoder = Some(RleEncoder::new(1, DEFAULT_RLE_BUFFER_LEN));
}
let rle_encoder = self.encoder.as_mut().unwrap();
for value in values {
if !rle_encoder.put(*value as u64)? {
return Err(general_err!("RLE buffer is full"));
}
}
Ok(())
}
#[inline]
fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
assert!(
self.encoder.is_some(),
"RLE value encoder is not initialized"
);
let rle_encoder = self.encoder.as_mut().unwrap();
// Flush all encoder buffers and raw values
let encoded_data = {
let buf = rle_encoder.flush_buffer()?;
// Note that buf does not have any offset, all data is encoded bytes
let len = (buf.len() as i32).to_le();
let len_bytes = len.as_bytes();
let mut encoded_data = Vec::new();
encoded_data.extend_from_slice(len_bytes);
encoded_data.extend_from_slice(buf);
encoded_data
};
// Reset rle encoder for the next batch
rle_encoder.clear();
Ok(ByteBufferPtr::new(encoded_data))
}
}
// ----------------------------------------------------------------------
// ::DeltaBinaryPacked encoding
const MAX_PAGE_HEADER_WRITER_SIZE: usize = 32;
const MAX_BIT_WRITER_SIZE: usize = 10 * 1024 * 1024;
const DEFAULT_BLOCK_SIZE: usize = 128;
const DEFAULT_NUM_MINI_BLOCKS: usize = 4;
/// Delta bit packed encoder.
/// Consists of a header followed by blocks of delta encoded values binary packed.
///
/// Delta-binary-packing:
/// ```shell
/// [page-header] [block 1], [block 2], ... [block N]
/// ```
///
/// Each page header consists of:
/// ```shell
/// [block size] [number of miniblocks in a block] [total value count] [first value]
/// ```
///
/// Each block consists of:
/// ```shell
/// [min delta] [list of bitwidths of miniblocks] [miniblocks]
/// ```
///
/// Current implementation writes values in `put` method, multiple calls to `put` to
/// existing block or start new block if block size is exceeded. Calling `flush_buffer`
/// writes out all data and resets internal state, including page header.
///
/// Supports only INT32 and INT64.
pub struct DeltaBitPackEncoder<T: DataType> {
page_header_writer: BitWriter,
bit_writer: BitWriter,
total_values: usize,
first_value: i64,
current_value: i64,
block_size: usize,
mini_block_size: usize,
num_mini_blocks: usize,
values_in_block: usize,
deltas: Vec<i64>,
_phantom: PhantomData<T>,
}
impl<T: DataType> DeltaBitPackEncoder<T> {
/// Creates new delta bit packed encoder.
pub fn new() -> Self {
let block_size = DEFAULT_BLOCK_SIZE;
let num_mini_blocks = DEFAULT_NUM_MINI_BLOCKS;
let mini_block_size = block_size / num_mini_blocks;
assert!(mini_block_size % 8 == 0);
Self::assert_supported_type();
DeltaBitPackEncoder {
page_header_writer: BitWriter::new(MAX_PAGE_HEADER_WRITER_SIZE),
bit_writer: BitWriter::new(MAX_BIT_WRITER_SIZE),
total_values: 0,
first_value: 0,
current_value: 0, // current value to keep adding deltas
block_size, // can write fewer values than block size for last block
mini_block_size,
num_mini_blocks,
values_in_block: 0, // will be at most block_size
deltas: vec![0; block_size],
_phantom: PhantomData,
}
}
/// Writes page header for blocks, this method is invoked when we are done encoding
/// values. It is also okay to encode when no values have been provided
fn write_page_header(&mut self) {
// We ignore the result of each 'put' operation, because
// MAX_PAGE_HEADER_WRITER_SIZE is chosen to fit all header values and
// guarantees that writes will not fail.
// Write the size of each block
self.page_header_writer
.put_vlq_int(self.block_size as u64)
.unwrap();
// Write the number of mini blocks
self.page_header_writer
.put_vlq_int(self.num_mini_blocks as u64)
.unwrap();
// Write the number of all values (including non-encoded first value)
self.page_header_writer
.put_vlq_int(self.total_values as u64)
.unwrap();
// Write first value
self.page_header_writer
.put_zigzag_vlq_int(self.first_value)
.unwrap();
}
// Write current delta buffer (<= 'block size' values) into bit writer
fn flush_block_values(&mut self) -> Result<()> {
if self.values_in_block == 0 {
return Ok(());
}
let mut min_delta = i64::max_value();
for i in 0..self.values_in_block {
min_delta = cmp::min(min_delta, self.deltas[i]);
}
// Write min delta
self.bit_writer.put_zigzag_vlq_int(min_delta)?;
let offset = self.bit_writer.skip(self.num_mini_blocks)?;
for i in 0..self.num_mini_blocks {
// Find how many values we need to encode - either block size or whatever
// values left
let n = cmp::min(self.mini_block_size, self.values_in_block);
if n == 0 {
break;
}
// Compute the max delta in current mini block
let mut max_delta = i64::min_value();
for j in 0..n {
max_delta = cmp::max(max_delta, self.deltas[i * self.mini_block_size + j]);
}
// Compute bit width to store (max_delta - min_delta)
let bit_width = num_required_bits(Self::subtract_u64(max_delta, min_delta));
self.bit_writer.buffer_set(offset + i, bit_width as u8);
// Encode values in current mini block using min_delta and bit_width
for j in 0..n {
let packed_value =
Self::subtract_u64(self.deltas[i * self.mini_block_size + j], min_delta);
self.bit_writer.put_value(packed_value, bit_width)?;
}
// Pad the last block (n < mini_block_size)
for _ in n..self.mini_block_size {
self.bit_writer.put_value(0, bit_width)?;
}
self.values_in_block -= n;
}
assert!(
self.values_in_block == 0,
"Expected 0 values in block, found {}",
self.values_in_block
);
Ok(())
}
}
// Implementation is shared between Int32Type and Int64Type,
// see `DeltaBitPackEncoderConversion` below for specifics.
impl<T: DataType> Encoder<T> for DeltaBitPackEncoder<T> {
fn put(&mut self, values: &[T::Type]) -> Result<()> {
if values.is_empty() {
return Ok(());
}
let mut idx;
// Define values to encode, initialize state
if self.total_values == 0 {
self.first_value = Self::as_i64(values, 0);
self.current_value = self.first_value;
idx = 1;
} else {
idx = 0;
}
// Add all values (including first value)
self.total_values += values.len();
// Write block
while idx < values.len() {
let value = Self::as_i64(values, idx);
self.deltas[self.values_in_block] = Self::subtract(value, self.current_value);
self.current_value = value;
idx += 1;
self.values_in_block += 1;
if self.values_in_block == self.block_size {
self.flush_block_values()?;
}
}
Ok(())
}
fn encoding(&self) -> Encoding {
Encoding::DeltaBinaryPacked
}
fn estimated_data_encoded_size(&self) -> usize {
self.bit_writer.bytes_written()
}
fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
// Write remaining values
self.flush_block_values()?;
// Write page header with total values
self.write_page_header();
let mut buffer = ByteBuffer::new();
buffer.write_all(self.page_header_writer.flush_buffer())?;
buffer.write_all(self.bit_writer.flush_buffer())?;
buffer.flush()?;
// Reset state
self.page_header_writer.clear();
self.bit_writer.clear();
self.total_values = 0;
self.first_value = 0;
self.current_value = 0;
self.values_in_block = 0;
Ok(buffer.consume())
}
}
/// Helper trait to define specific conversions and subtractions when computing deltas
trait DeltaBitPackEncoderConversion<T: DataType> {
// Method should panic if type is not supported, otherwise no-op
fn assert_supported_type();
fn as_i64(values: &[T::Type], index: usize) -> i64;
fn subtract(left: i64, right: i64) -> i64;
fn subtract_u64(left: i64, right: i64) -> u64;
}
impl<T: DataType> DeltaBitPackEncoderConversion<T> for DeltaBitPackEncoder<T> {
#[inline]
default fn assert_supported_type() {
panic!("DeltaBitPackDecoder only supports Int32Type and Int64Type");
}
#[inline]
default fn as_i64(_values: &[T::Type], _index: usize) -> i64 {
0
}
#[inline]
default fn subtract(_left: i64, _right: i64) -> i64 {
0
}
#[inline]
default fn subtract_u64(_left: i64, _right: i64) -> u64 {
0
}
}
impl DeltaBitPackEncoderConversion<Int32Type> for DeltaBitPackEncoder<Int32Type> {
#[inline]
fn assert_supported_type() {
// no-op: supported type
}
#[inline]
fn as_i64(values: &[i32], index: usize) -> i64 {
values[index] as i64
}
#[inline]
fn subtract(left: i64, right: i64) -> i64 {
// It is okay for values to overflow, wrapping_sub wrapping around at the boundary
(left as i32).wrapping_sub(right as i32) as i64
}
#[inline]
fn subtract_u64(left: i64, right: i64) -> u64 {
// Conversion of i32 -> u32 -> u64 is to avoid non-zero left most bytes in int
// representation
(left as i32).wrapping_sub(right as i32) as u32 as u64
}
}
impl DeltaBitPackEncoderConversion<Int64Type> for DeltaBitPackEncoder<Int64Type> {
#[inline]
fn assert_supported_type() {
// no-op: supported type
}
#[inline]
fn as_i64(values: &[i64], index: usize) -> i64 {
values[index]
}
#[inline]
fn subtract(left: i64, right: i64) -> i64 {
// It is okay for values to overflow, wrapping_sub wrapping around at the boundary
left.wrapping_sub(right)
}
#[inline]
fn subtract_u64(left: i64, right: i64) -> u64 {
left.wrapping_sub(right) as u64
}
}
// ----------------------------------------------------------------------
// DELTA_LENGTH_BYTE_ARRAY encoding
/// Encoding for byte arrays to separate the length values and the data.
/// The lengths are encoded using ::DeltaBinaryPacked encoding, data is
/// stored as raw bytes.
pub struct DeltaLengthByteArrayEncoder<T: DataType> {
// length encoder
len_encoder: DeltaBitPackEncoder<Int32Type>,
// byte array data
data: Vec<ByteArray>,
// data size in bytes of encoded values
encoded_size: usize,
_phantom: PhantomData<T>,
}
impl<T: DataType> DeltaLengthByteArrayEncoder<T> {
/// Creates new delta length byte array encoder.
pub fn new() -> Self {
Self {
len_encoder: DeltaBitPackEncoder::new(),
data: vec![],
encoded_size: 0,
_phantom: PhantomData,
}
}
}
impl<T: DataType> Encoder<T> for DeltaLengthByteArrayEncoder<T> {
default fn put(&mut self, _values: &[T::Type]) -> Result<()> {
panic!("DeltaLengthByteArrayEncoder only supports ByteArrayType");
}
fn encoding(&self) -> Encoding {
Encoding::DeltaLengthByteArray
}
fn estimated_data_encoded_size(&self) -> usize {
self.len_encoder.estimated_data_encoded_size() + self.encoded_size
}
default fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
panic!("DeltaLengthByteArrayEncoder only supports ByteArrayType");
}
}
impl Encoder<ByteArrayType> for DeltaLengthByteArrayEncoder<ByteArrayType> {
fn put(&mut self, values: &[ByteArray]) -> Result<()> {
let lengths: Vec<i32> = values
.iter()
.map(|byte_array| byte_array.len() as i32)
.collect();
self.len_encoder.put(&lengths)?;
for byte_array in values {
self.encoded_size += byte_array.len();
self.data.push(byte_array.clone());
}
Ok(())
}
fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
let mut total_bytes = vec![];
let lengths = self.len_encoder.flush_buffer()?;
total_bytes.extend_from_slice(lengths.data());
self.data.iter().for_each(|byte_array| {
total_bytes.extend_from_slice(byte_array.data());
});
self.data.clear();
self.encoded_size = 0;
Ok(ByteBufferPtr::new(total_bytes))
}
}
// ----------------------------------------------------------------------
// DELTA_BYTE_ARRAY encoding
/// Encoding for byte arrays, prefix lengths are encoded using ::DeltaBinaryPacked
/// encoding, followed by suffixes with DELTA_LENGTH_BYTE_ARRAY encoding.
pub struct DeltaByteArrayEncoder<T: DataType> {
prefix_len_encoder: DeltaBitPackEncoder<Int32Type>,
suffix_writer: DeltaLengthByteArrayEncoder<T>,
previous: Vec<u8>,
_phantom: PhantomData<T>,
}
impl<T: DataType> DeltaByteArrayEncoder<T> {
/// Creates new delta byte array encoder.
pub fn new() -> Self {
Self {
prefix_len_encoder: DeltaBitPackEncoder::<Int32Type>::new(),
suffix_writer: DeltaLengthByteArrayEncoder::<T>::new(),
previous: vec![],
_phantom: PhantomData,
}
}
}
impl<T: DataType> Encoder<T> for DeltaByteArrayEncoder<T> {
default fn put(&mut self, _values: &[T::Type]) -> Result<()> {
panic!("DeltaByteArrayEncoder only supports ByteArrayType and FixedLenByteArrayType");
}
fn encoding(&self) -> Encoding {
Encoding::DeltaByteArray
}
fn estimated_data_encoded_size(&self) -> usize {
self.prefix_len_encoder.estimated_data_encoded_size()
+ self.suffix_writer.estimated_data_encoded_size()
}
default fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
panic!("DeltaByteArrayEncoder only supports ByteArrayType and FixedLenByteArrayType");
}
}
impl Encoder<ByteArrayType> for DeltaByteArrayEncoder<ByteArrayType> {
fn put(&mut self, values: &[ByteArray]) -> Result<()> {
let mut prefix_lengths: Vec<i32> = vec![];
let mut suffixes: Vec<ByteArray> = vec![];
for byte_array in values {
let current = byte_array.data();
// Maximum prefix length that is shared between previous value and current
// value
let prefix_len = cmp::min(self.previous.len(), current.len());
let mut match_len = 0;
while match_len < prefix_len && self.previous[match_len] == current[match_len] {
match_len += 1;
}
prefix_lengths.push(match_len as i32);
suffixes.push(byte_array.slice(match_len, byte_array.len() - match_len));
// Update previous for the next prefix
self.previous.clear();
self.previous.extend_from_slice(current);
}
self.prefix_len_encoder.put(&prefix_lengths)?;
self.suffix_writer.put(&suffixes)?;
Ok(())
}
fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
// TODO: investigate if we can merge lengths and suffixes
// without copying data into new vector.
let mut total_bytes = vec![];
// Insert lengths ...
let lengths = self.prefix_len_encoder.flush_buffer()?;
total_bytes.extend_from_slice(lengths.data());
// ... followed by suffixes
let suffixes = self.suffix_writer.flush_buffer()?;
total_bytes.extend_from_slice(suffixes.data());
self.previous.clear();
Ok(ByteBufferPtr::new(total_bytes))
}
}
impl Encoder<FixedLenByteArrayType> for DeltaByteArrayEncoder<FixedLenByteArrayType> {
fn put(&mut self, values: &[ByteArray]) -> Result<()> {
let s: &mut DeltaByteArrayEncoder<ByteArrayType> = unsafe { mem::transmute(self) };
s.put(values)
}
fn flush_buffer(&mut self) -> Result<ByteBufferPtr> {
let s: &mut DeltaByteArrayEncoder<ByteArrayType> = unsafe { mem::transmute(self) };
s.flush_buffer()
}
}
#[cfg(test)]
mod tests {
use std::rc::Rc;
use test::Bencher;
use super::*;
use crate::internal::{