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|
use super::common::*;
use priority_queue::PriorityQueue;
use std::collections::BTreeMap;
use std::collections::HashSet;
use std::fmt::Debug;
use std::hash::{Hash, Hasher};
struct UniqueRecord {
/// The value of the record's primary key field
primary_value: IndexableValue,
/// The record itself.
record: Record,
}
impl PartialEq for UniqueRecord {
fn eq(&self, other: &UniqueRecord) -> bool {
self.primary_value == other.primary_value
}
}
impl Eq for UniqueRecord {}
impl Hash for UniqueRecord {
fn hash<H>(&self, state: &mut H)
where
H: Hasher,
{
self.primary_value.hash(state)
}
}
pub struct SecondaryMemtable<Field: Eq + Clone + Debug> {
pub field: Field,
pub primary_field_index: usize,
capacity: usize,
/// Running counter of memtable operations, used as priority
/// in evict_queue.
n_operations: u64,
records: BTreeMap<IndexableValue, HashSet<UniqueRecord>>,
/// A max heap priority queue of keys. Note: n_operations must
/// be negated upon append to evict oldest values first.
evict_queue: PriorityQueue<IndexableValue, i64>,
evict_policy: MemtableEvictPolicy,
}
impl<Field: Eq + Clone + Debug> SecondaryMemtable<Field> {
pub fn new(
field: &Field,
primary_field_index: usize,
capacity: usize,
evict_policy: MemtableEvictPolicy,
) -> SecondaryMemtable<Field> {
SecondaryMemtable {
field: field.clone(),
primary_field_index,
capacity,
n_operations: 0,
records: BTreeMap::new(),
evict_queue: PriorityQueue::new(),
evict_policy,
}
}
pub fn set(&mut self, key: &IndexableValue, value: &Record) {
if self.capacity == 0 {
return;
}
debug!(
"Inserting/updating record in secondary memtable with key {:?} = {:?}",
&key, &value,
);
if self.records.len() >= self.capacity {
let (evict_key, _prio) = self.evict_queue.pop().expect("Evict queue was empty");
self.records.remove(&evict_key);
}
let unique_record = UniqueRecord {
primary_value: value.values[self.primary_field_index]
.as_indexable()
.expect("Value at primary field index was not indexable"),
record: value.clone(),
};
match self.records.get_mut(key) {
Some(existing) => {
debug!(
"Existing entry found with {} records in the set",
&existing.len()
);
existing.insert(unique_record);
}
None => {
debug!("No existing entry found, creating one.");
let mut set = HashSet::with_capacity(1);
set.insert(unique_record);
self.records.insert(key.clone(), set);
}
}
if self.evict_policy == MemtableEvictPolicy::LeastWritten
|| self.evict_policy == MemtableEvictPolicy::LeastReadOrWritten
{
self.set_priority(&key);
}
}
pub fn set_all(&mut self, key: &IndexableValue, values: &[Record]) {
if self.capacity == 0 {
return;
}
debug!(
"Replacing set of records in secondary memtable with key {:?} ({} values)",
&key,
&values.len(),
);
if self.records.len() >= self.capacity {
let (evict_key, _prio) = self.evict_queue.pop().expect("Evict queue was empty");
self.records.remove(&evict_key);
}
let mut set = HashSet::with_capacity(values.len());
values.iter().for_each(|value| {
let unique_record = UniqueRecord {
primary_value: value.values[self.primary_field_index]
.as_indexable()
.expect("Value at primary field index was not indexable"),
record: value.clone(),
};
set.insert(unique_record);
});
self.records.insert(key.clone(), set);
if self.evict_policy == MemtableEvictPolicy::LeastWritten
|| self.evict_policy == MemtableEvictPolicy::LeastReadOrWritten
{
self.set_priority(&key);
}
}
pub fn find_all(&mut self, key: &IndexableValue) -> Vec<&Record> {
if self.evict_policy == MemtableEvictPolicy::LeastRead
|| self.evict_policy == MemtableEvictPolicy::LeastReadOrWritten
{
self.set_priority(&key);
}
match self.records.get(key) {
None => vec![],
Some(set) => set
.iter()
.map(|unique_record| &unique_record.record)
.collect(),
}
}
fn set_priority(&mut self, key: &IndexableValue) {
let priority = self.get_and_increment_current_priority();
match self.evict_queue.get(key) {
Some(_) => {
self.evict_queue.change_priority(key, priority);
}
None => {
self.evict_queue.push(key.clone(), priority);
}
}
}
fn get_and_increment_current_priority(&mut self) -> i64 {
let ret = -(self.n_operations as i64);
self.n_operations += 1;
ret
}
}
|
