Jimexist commented on code in PR #3057: URL: https://github.com/apache/arrow-rs/pull/3057#discussion_r1020311911
########## parquet/src/bloom_filter/mod.rs: ########## @@ -0,0 +1,212 @@ +// 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. + +//! Bloom filter implementation specific to Parquet, as described +//! in the [spec](https://github.com/apache/parquet-format/blob/master/BloomFilter.md) + +use crate::errors::ParquetError; +use crate::file::metadata::ColumnChunkMetaData; +use crate::format::{ + BloomFilterAlgorithm, BloomFilterCompression, BloomFilterHash, BloomFilterHeader, +}; +use std::hash::Hasher; +use std::io::{Read, Seek, SeekFrom}; +use thrift::protocol::TCompactInputProtocol; +use twox_hash::XxHash64; + +const SALT: [u32; 8] = [ + 0x47b6137b_u32, + 0x44974d91_u32, + 0x8824ad5b_u32, + 0xa2b7289d_u32, + 0x705495c7_u32, + 0x2df1424b_u32, + 0x9efc4947_u32, + 0x5c6bfb31_u32, +]; + +/// Each block is 256 bits, broken up into eight contiguous "words", each consisting of 32 bits. +/// Each word is thought of as an array of bits; each bit is either "set" or "not set". +type Block = [u32; 8]; + +/// takes as its argument a single unsigned 32-bit integer and returns a block in which each +/// word has exactly one bit set. +fn mask(x: u32) -> Block { + let mut result = [0_u32; 8]; + for i in 0..8 { + // wrapping instead of checking for overflow + let y = x.wrapping_mul(SALT[i]); + let y = y >> 27; + result[i] = 1 << y; + } + result +} + +/// setting every bit in the block that was also set in the result from mask +fn block_insert(block: &mut Block, hash: u32) { + let mask = mask(hash); + for i in 0..8 { + block[i] |= mask[i]; + } +} + +/// returns true when every bit that is set in the result of mask is also set in the block. +fn block_check(block: &Block, hash: u32) -> bool { + let mask = mask(hash); + for i in 0..8 { + if block[i] & mask[i] == 0 { + return false; + } + } + true +} + +/// A split block Bloom filter +pub struct Sbbf(Vec<Block>); + +impl Sbbf { + fn new(bitset: &[u8]) -> Self { + let data = bitset + .chunks_exact(4 * 8) + .map(|chunk| { + let mut block = [0_u32; 8]; + for (i, word) in chunk.chunks_exact(4).enumerate() { + block[i] = u32::from_le_bytes(word.try_into().unwrap()); + } + block + }) + .collect::<Vec<Block>>(); + Self(data) + } + + pub fn read_from_column_chunk<R: Read + Seek>( Review Comment: yes eventually, but i think it can be done later after being used in the reader, likely `RowGroupReader`. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
