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bitpacked.rs
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bitpacked.rs
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use std::io::{self, Write};
use common::BinarySerializable;
use tantivy_bitpacker::{compute_num_bits, BitPacker, BitUnpacker};
use crate::{FastFieldCodecReader, FastFieldCodecSerializer, FastFieldDataAccess, FastFieldStats};
/// Depending on the field type, a different
/// fast field is required.
#[derive(Clone)]
pub struct BitpackedFastFieldReader {
bit_unpacker: BitUnpacker,
pub min_value_u64: u64,
pub max_value_u64: u64,
}
impl FastFieldCodecReader for BitpackedFastFieldReader {
/// Opens a fast field given a file.
fn open_from_bytes(bytes: &[u8]) -> io::Result<Self> {
let (_data, mut footer) = bytes.split_at(bytes.len() - 16);
let min_value = u64::deserialize(&mut footer)?;
let amplitude = u64::deserialize(&mut footer)?;
let max_value = min_value + amplitude;
let num_bits = compute_num_bits(amplitude);
let bit_unpacker = BitUnpacker::new(num_bits);
Ok(BitpackedFastFieldReader {
min_value_u64: min_value,
max_value_u64: max_value,
bit_unpacker,
})
}
#[inline]
fn get_u64(&self, doc: u64, data: &[u8]) -> u64 {
self.min_value_u64 + self.bit_unpacker.get(doc, data)
}
#[inline]
fn min_value(&self) -> u64 {
self.min_value_u64
}
#[inline]
fn max_value(&self) -> u64 {
self.max_value_u64
}
}
pub struct BitpackedFastFieldSerializerLegacy<'a, W: 'a + Write> {
bit_packer: BitPacker,
write: &'a mut W,
min_value: u64,
amplitude: u64,
num_bits: u8,
}
impl<'a, W: Write> BitpackedFastFieldSerializerLegacy<'a, W> {
/// Creates a new fast field serializer.
///
/// The serializer in fact encode the values by bitpacking
/// `(val - min_value)`.
///
/// It requires a `min_value` and a `max_value` to compute
/// compute the minimum number of bits required to encode
/// values.
pub fn open(
write: &'a mut W,
min_value: u64,
max_value: u64,
) -> io::Result<BitpackedFastFieldSerializerLegacy<'a, W>> {
assert!(min_value <= max_value);
let amplitude = max_value - min_value;
let num_bits = compute_num_bits(amplitude);
let bit_packer = BitPacker::new();
Ok(BitpackedFastFieldSerializerLegacy {
bit_packer,
write,
min_value,
amplitude,
num_bits,
})
}
/// Pushes a new value to the currently open u64 fast field.
#[inline]
pub fn add_val(&mut self, val: u64) -> io::Result<()> {
let val_to_write: u64 = val - self.min_value;
self.bit_packer
.write(val_to_write, self.num_bits, &mut self.write)?;
Ok(())
}
pub fn close_field(mut self) -> io::Result<()> {
self.bit_packer.close(&mut self.write)?;
self.min_value.serialize(&mut self.write)?;
self.amplitude.serialize(&mut self.write)?;
Ok(())
}
}
pub struct BitpackedFastFieldSerializer {}
impl FastFieldCodecSerializer for BitpackedFastFieldSerializer {
const NAME: &'static str = "Bitpacked";
const ID: u8 = 1;
/// Serializes data with the BitpackedFastFieldSerializer.
///
/// The serializer in fact encode the values by bitpacking
/// `(val - min_value)`.
///
/// It requires a `min_value` and a `max_value` to compute
/// compute the minimum number of bits required to encode
/// values.
fn serialize(
write: &mut impl Write,
_fastfield_accessor: &dyn FastFieldDataAccess,
stats: FastFieldStats,
data_iter: impl Iterator<Item = u64>,
_data_iter1: impl Iterator<Item = u64>,
) -> io::Result<()> {
let mut serializer =
BitpackedFastFieldSerializerLegacy::open(write, stats.min_value, stats.max_value)?;
for val in data_iter {
serializer.add_val(val)?;
}
serializer.close_field()?;
Ok(())
}
fn is_applicable(
_fastfield_accessor: &impl FastFieldDataAccess,
_stats: FastFieldStats,
) -> bool {
true
}
fn estimate(_fastfield_accessor: &impl FastFieldDataAccess, stats: FastFieldStats) -> f32 {
let amplitude = stats.max_value - stats.min_value;
let num_bits = compute_num_bits(amplitude);
let num_bits_uncompressed = 64;
num_bits as f32 / num_bits_uncompressed as f32
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::tests::get_codec_test_data_sets;
fn create_and_validate(data: &[u64], name: &str) {
crate::tests::create_and_validate::<BitpackedFastFieldSerializer, BitpackedFastFieldReader>(
data, name,
);
}
#[test]
fn test_with_codec_data_sets() {
let data_sets = get_codec_test_data_sets();
for (mut data, name) in data_sets {
create_and_validate(&data, name);
data.reverse();
create_and_validate(&data, name);
}
}
#[test]
fn bitpacked_fast_field_rand() {
for _ in 0..500 {
let mut data = (0..1 + rand::random::<u8>() as usize)
.map(|_| rand::random::<i64>() as u64 / 2)
.collect::<Vec<_>>();
create_and_validate(&data, "rand");
data.reverse();
create_and_validate(&data, "rand");
}
}
}