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parallel.rs
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parallel.rs
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use core::slice;
use std::fs::File;
use std::io::{BufWriter, Write};
use std::marker;
use std::path::Path;
use std::sync::atomic::{AtomicBool, AtomicU32, AtomicU64, Ordering};
use heed::types::Bytes;
use heed::{BytesDecode, BytesEncode, RoTxn};
use memmap2::Mmap;
use rand::seq::index;
use rand::Rng;
use roaring::RoaringBitmap;
use crate::internals::{KeyCodec, Leaf, NodeCodec};
use crate::key::{Prefix, PrefixCodec};
use crate::node::Node;
use crate::{Database, Distance, Error, ItemId, Result};
/// A structure to store the tree nodes out of the heed database.
pub struct TmpNodes<DE> {
file: BufWriter<File>,
ids: Vec<ItemId>,
bounds: Vec<usize>,
deleted: RoaringBitmap,
_marker: marker::PhantomData<DE>,
}
impl<'a, DE: BytesEncode<'a>> TmpNodes<DE> {
/// Creates an empty `TmpNodes`.
pub fn new() -> heed::Result<TmpNodes<DE>> {
Ok(TmpNodes {
file: tempfile::tempfile().map(BufWriter::new)?,
ids: Vec::new(),
bounds: vec![0],
deleted: RoaringBitmap::new(),
_marker: marker::PhantomData,
})
}
/// Creates an empty `TmpNodes` in the defined folder.
pub fn new_in(path: &Path) -> heed::Result<TmpNodes<DE>> {
Ok(TmpNodes {
file: tempfile::tempfile_in(path).map(BufWriter::new)?,
ids: Vec::new(),
bounds: vec![0],
deleted: RoaringBitmap::new(),
_marker: marker::PhantomData,
})
}
/// Add a new node in the file.
/// Items do not need to be ordered.
pub fn put(
// TODO move that in the type
&mut self,
item: ItemId,
data: &'a DE::EItem,
) -> heed::Result<()> {
assert!(item != ItemId::MAX);
let bytes = DE::bytes_encode(data).map_err(heed::Error::Encoding)?;
self.file.write_all(&bytes)?;
let last_bound = self.bounds.last().unwrap();
self.bounds.push(last_bound + bytes.len());
self.ids.push(item);
// in the current algorithm, we should never insert a node that was deleted before
debug_assert!(!self.deleted.contains(item));
Ok(())
}
/// Mark a node to delete from the DB.
pub fn remove_from_db(&mut self, item: ItemId) {
self.deleted.insert(item);
}
/// Mark a node to delete from the DB and delete it from the tmp nodes as well.
/// Panic if the node wasn't inserted in the tmp_nodes before calling this method.
pub fn remove(&mut self, item: ItemId) -> heed::Result<()> {
self.remove_from_db(item);
// In the current algorithm, we're supposed to find the node in the two last positions.
if let Some(el) = self.ids.iter_mut().rev().take(2).find(|i| **i == item) {
*el = u32::MAX;
} else {
unreachable!();
}
Ok(())
}
/// Converts it into a readers to be able to read the nodes.
pub fn into_bytes_reader(self) -> Result<TmpNodesReader> {
let file = self.file.into_inner().map_err(|iie| iie.into_error())?;
let mmap = unsafe { Mmap::map(&file)? };
#[cfg(unix)]
mmap.advise(memmap2::Advice::Sequential)?;
Ok(TmpNodesReader { mmap, ids: self.ids, bounds: self.bounds, deleted: self.deleted })
}
}
/// A reader of nodes stored in a file.
pub struct TmpNodesReader {
mmap: Mmap,
ids: Vec<ItemId>,
bounds: Vec<usize>,
deleted: RoaringBitmap,
}
impl TmpNodesReader {
/// The number of nodes stored in this file.
pub fn len(&self) -> usize {
self.ids.len()
}
pub fn to_delete(&self) -> impl Iterator<Item = ItemId> + '_ {
self.deleted.iter()
}
/// Returns an forward iterator over the nodes.
pub fn to_insert(&self) -> impl Iterator<Item = (ItemId, &[u8])> {
self.ids
.iter()
.zip(self.bounds.windows(2))
.map(|(id, bounds)| {
let [start, end] = [bounds[0], bounds[1]];
(*id, &self.mmap[start..end])
})
.filter(|(id, _)| *id != ItemId::MAX)
}
}
/// A concurrent ID generate that will never return the same ID twice.
#[derive(Debug)]
pub struct ConcurrentNodeIds {
/// The current tree node ID we should use if there is no other IDs available.
current: AtomicU32,
/// The total number of tree node IDs used.
used: AtomicU64,
/// A list of IDs to exhaust before picking IDs from `current`.
available: RoaringBitmap,
/// The current Nth ID to select in the bitmap.
select_in_bitmap: AtomicU32,
/// Tells if you should look in the roaring bitmap or if all the IDs are already exhausted.
look_into_bitmap: AtomicBool,
}
impl ConcurrentNodeIds {
/// Creates an ID generator returning unique IDs, avoiding the specified used IDs.
pub fn new(used: RoaringBitmap) -> ConcurrentNodeIds {
let last_id = used.max().map_or(0, |id| id + 1);
let used_ids = used.len();
let available = RoaringBitmap::from_sorted_iter(0..last_id).unwrap() - used;
ConcurrentNodeIds {
current: AtomicU32::new(last_id),
used: AtomicU64::new(used_ids),
select_in_bitmap: AtomicU32::new(0),
look_into_bitmap: AtomicBool::new(!available.is_empty()),
available,
}
}
/// Returns a new unique ID and increase the count of IDs used.
pub fn next(&self) -> Result<u32> {
if self.used.fetch_add(1, Ordering::Relaxed) > u32::MAX as u64 {
Err(Error::DatabaseFull)
} else if self.look_into_bitmap.load(Ordering::Relaxed) {
let current = self.select_in_bitmap.fetch_add(1, Ordering::Relaxed);
match self.available.select(current) {
Some(id) => Ok(id),
None => {
self.look_into_bitmap.store(false, Ordering::Relaxed);
Ok(self.current.fetch_add(1, Ordering::Relaxed))
}
}
} else {
Ok(self.current.fetch_add(1, Ordering::Relaxed))
}
}
/// Returns the number of used ids in total.
pub fn used(&self) -> u64 {
self.used.load(Ordering::Relaxed)
}
}
/// A struture used to keep a list of the leaf nodes in the tree.
///
/// It is safe to share between threads as the pointer are pointing
/// in the mmapped file and the transaction is kept here and therefore
/// no longer touches the database.
pub struct ImmutableLeafs<'t, D> {
leaf_ids: RoaringBitmap,
constant_length: Option<usize>,
offsets: Vec<*const u8>,
_marker: marker::PhantomData<(&'t (), D)>,
}
impl<'t, D: Distance> ImmutableLeafs<'t, D> {
/// Creates the structure by fetching all the leaf pointers
/// and keeping the transaction making the pointers valid.
pub fn new(rtxn: &'t RoTxn, database: Database<D>, index: u16) -> heed::Result<Self> {
let mut leaf_ids = RoaringBitmap::new();
let mut constant_length = None;
let mut offsets = Vec::new();
let iter = database
.remap_types::<PrefixCodec, Bytes>()
.prefix_iter(rtxn, &Prefix::item(index))?
.remap_key_type::<KeyCodec>();
for result in iter {
let (key, bytes) = result?;
let item_id = key.node.unwrap_item();
assert_eq!(*constant_length.get_or_insert(bytes.len()), bytes.len());
assert!(leaf_ids.push(item_id));
offsets.push(bytes.as_ptr());
}
Ok(ImmutableLeafs { leaf_ids, constant_length, offsets, _marker: marker::PhantomData })
}
/// Returns the leafs identified by the given ID.
pub fn get(&self, item_id: ItemId) -> heed::Result<Option<Leaf<'t, D>>> {
let len = match self.constant_length {
Some(len) => len,
None => return Ok(None),
};
let ptr = match self
.leaf_ids
.rank(item_id)
.checked_sub(1)
.and_then(|offset| self.offsets.get(offset as usize))
{
Some(ptr) => *ptr,
None => return Ok(None),
};
let bytes = unsafe { slice::from_raw_parts(ptr, len) };
NodeCodec::bytes_decode(bytes).map_err(heed::Error::Decoding).map(|node| node.leaf())
}
}
unsafe impl<D> Sync for ImmutableLeafs<'_, D> {}
/// A subset of leafs that are accessible for read.
pub struct ImmutableSubsetLeafs<'t, D> {
subset: &'t RoaringBitmap,
leafs: &'t ImmutableLeafs<'t, D>,
}
impl<'t, D: Distance> ImmutableSubsetLeafs<'t, D> {
/// Creates a subset view of the available leafs.
pub fn from_item_ids(leafs: &'t ImmutableLeafs<'t, D>, subset: &'t RoaringBitmap) -> Self {
ImmutableSubsetLeafs { subset, leafs }
}
/// Returns the leafs identified by the given ID in the subset.
pub fn get(&self, item_id: ItemId) -> heed::Result<Option<Leaf<'t, D>>> {
if self.subset.contains(item_id) {
self.leafs.get(item_id)
} else {
Ok(None)
}
}
/// Randomly selects two leafs verified to be different.
pub fn choose_two<R: Rng>(&self, rng: &mut R) -> heed::Result<Option<[Leaf<'t, D>; 2]>> {
let indexes = index::sample(rng, self.subset.len() as usize, 2);
let first = match self.subset.select(indexes.index(0) as u32) {
Some(item_id) => self.leafs.get(item_id)?,
None => None,
};
let second = match self.subset.select(indexes.index(1) as u32) {
Some(item_id) => self.leafs.get(item_id)?,
None => None,
};
Ok(first.zip(second).map(|(a, b)| [a, b]))
}
/// Randomly select one leaf out of this subset.
pub fn choose<R: Rng>(&self, rng: &mut R) -> heed::Result<Option<Leaf<'t, D>>> {
if self.subset.is_empty() {
Ok(None)
} else {
let ubound = (self.subset.len() - 1) as u32;
let index = rng.gen_range(0..=ubound);
match self.subset.select(index) {
Some(item_id) => self.leafs.get(item_id),
None => Ok(None),
}
}
}
}
/// A struture used to keep a list of all the tree nodes in the tree.
///
/// It is safe to share between threads as the pointer are pointing
/// in the mmapped file and the transaction is kept here and therefore
/// no longer touches the database.
pub struct ImmutableTrees<'t, D> {
tree_ids: RoaringBitmap,
offsets: Vec<*const u8>,
lengths: Vec<usize>,
_marker: marker::PhantomData<(&'t (), D)>,
}
impl<'t, D: Distance> ImmutableTrees<'t, D> {
/// Creates the structure by fetching all the root pointers
/// and keeping the transaction making the pointers valid.
pub fn new(rtxn: &'t RoTxn, database: Database<D>, index: u16) -> heed::Result<Self> {
let mut tree_ids = RoaringBitmap::new();
let mut offsets = Vec::new();
let mut lengths = Vec::new();
let iter = database
.remap_types::<PrefixCodec, Bytes>()
.prefix_iter(rtxn, &Prefix::tree(index))?
.remap_key_type::<KeyCodec>();
for result in iter {
let (key, bytes) = result?;
let tree_id = key.node.unwrap_tree();
assert!(tree_ids.push(tree_id));
offsets.push(bytes.as_ptr());
lengths.push(bytes.len());
}
Ok(ImmutableTrees { tree_ids, lengths, offsets, _marker: marker::PhantomData })
}
/// Returns the tree node identified by the given ID.
pub fn get(&self, item_id: ItemId) -> heed::Result<Option<Node<'t, D>>> {
let (ptr, len) = match self.tree_ids.rank(item_id).checked_sub(1).and_then(|offset| {
self.offsets.get(offset as usize).zip(self.lengths.get(offset as usize))
}) {
Some((ptr, len)) => (*ptr, *len),
None => return Ok(None),
};
let bytes = unsafe { slice::from_raw_parts(ptr, len) };
NodeCodec::bytes_decode(bytes).map_err(heed::Error::Decoding).map(Some)
}
}
unsafe impl<D> Sync for ImmutableTrees<'_, D> {}