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use super::common::*;
use priority_queue::PriorityQueue;
use std::collections::BTreeMap;
pub struct PrimaryMemtable {
capacity: usize,
/// Running counter of memtable operations, used as priority
/// in evict_queue.
n_operations: u64,
records: BTreeMap<IndexableValue, Record>,
/// 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 PrimaryMemtable {
pub fn new(capacity: usize, evict_policy: MemtableEvictPolicy) -> PrimaryMemtable {
PrimaryMemtable {
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 primary 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);
}
self.records.insert(key.clone(), value.clone());
if self.evict_policy == MemtableEvictPolicy::LeastWritten
|| self.evict_policy == MemtableEvictPolicy::LeastReadOrWritten
{
self.set_priority(&key);
}
}
pub fn get(&mut self, key: &IndexableValue) -> Option<&Record> {
if self.evict_policy == MemtableEvictPolicy::LeastRead
|| self.evict_policy == MemtableEvictPolicy::LeastReadOrWritten
{
self.set_priority(&key);
}
self.records.get(key)
}
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
}
}
|
