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/*
* include/shard/PGM.h
*
* Copyright (C) 2023 Douglas B. Rumbaugh <drumbaugh@psu.edu>
* Dong Xie <dongx@psu.edu>
*
* Distributed under the Modified BSD License.
*
* A shard shim around the static version of the PGM learned
* index.
*
* TODO: The code in this file is very poorly commented.
*/
#pragma once
#include <vector>
#include "framework/ShardRequirements.h"
#include "pgm/pgm_index.hpp"
#include "psu-ds/BloomFilter.h"
#include "util/SortedMerge.h"
#include "util/bf_config.h"
using psudb::CACHELINE_SIZE;
using psudb::BloomFilter;
using psudb::PriorityQueue;
using psudb::queue_record;
using psudb::byte;
namespace de {
template <RecordInterface R, size_t epsilon=128>
class PGM {
private:
typedef decltype(R::key) K;
typedef decltype(R::value) V;
public:
PGM(BufferView<R> buffer)
: m_bf(nullptr)
, m_reccnt(0)
, m_tombstone_cnt(0)
, m_alloc_size(0) {
m_alloc_size = psudb::sf_aligned_alloc(CACHELINE_SIZE,
buffer.get_record_count() *
sizeof(Wrapped<R>),
(byte**) &m_data);
auto res = sorted_array_from_bufferview<R>(std::move(buffer), m_data, m_bf);
m_reccnt = res.record_count;
m_tombstone_cnt = res.tombstone_count;
if (m_reccnt > 0) {
std::vector<K> keys;
for (size_t i=0; i<m_reccnt; i++) {
keys.emplace_back(m_data[i].rec.key);
}
m_pgm = pgm::PGMIndex<K, epsilon>(keys);
}
}
PGM(std::vector<PGM*> shards)
: m_data(nullptr)
, m_bf(nullptr)
, m_reccnt(0)
, m_tombstone_cnt(0)
, m_alloc_size(0) {
size_t attemp_reccnt = 0;
size_t tombstone_count = 0;
auto cursors = build_cursor_vec<R, PGM>(shards, &attemp_reccnt, &tombstone_count);
m_bf = new BloomFilter<R>(BF_FPR, tombstone_count, BF_HASH_FUNCS);
m_alloc_size = psudb::sf_aligned_alloc(CACHELINE_SIZE,
attemp_reccnt * sizeof(Wrapped<R>),
(byte **) &m_data);
auto res = sorted_array_merge<R>(cursors, m_data, m_bf);
m_reccnt = res.record_count;
m_tombstone_cnt = res.tombstone_count;
if (m_reccnt > 0) {
std::vector<K> keys;
for (size_t i=0; i<m_reccnt; i++) {
keys.emplace_back(m_data[i].rec.key);
}
m_pgm = pgm::PGMIndex<K, epsilon>(keys);
}
}
~PGM() {
free(m_data);
delete m_bf;
}
Wrapped<R> *point_lookup(const R &rec, bool filter=false) {
size_t idx = get_lower_bound(rec.key);
if (idx >= m_reccnt) {
return nullptr;
}
while (idx < m_reccnt && m_data[idx].rec < rec) ++idx;
if (m_data[idx].rec == rec) {
return m_data + idx;
}
return nullptr;
}
Wrapped<R>* get_data() const {
return m_data;
}
size_t get_record_count() const {
return m_reccnt;
}
size_t get_tombstone_count() const {
return m_tombstone_cnt;
}
const Wrapped<R>* get_record_at(size_t idx) const {
if (idx >= m_reccnt) return nullptr;
return m_data + idx;
}
size_t get_memory_usage() {
return m_pgm.size_in_bytes();
}
size_t get_aux_memory_usage() {
return (m_bf) ? m_bf->memory_usage() : 0;
}
size_t get_lower_bound(const K& key) const {
auto bound = m_pgm.search(key);
size_t idx = bound.lo;
if (idx >= m_reccnt) {
return m_reccnt;
}
/*
* If the region to search is less than some pre-specified
* amount, perform a linear scan to locate the record.
*/
if (bound.hi - bound.lo < 256) {
while (idx < bound.hi && m_data[idx].rec.key < key) {
idx++;
}
} else {
/* Otherwise, perform a binary search */
idx = bound.lo;
size_t max = bound.hi;
while (idx < max) {
size_t mid = (idx + max) / 2;
if (key > m_data[mid].rec.key) {
idx = mid + 1;
} else {
max = mid;
}
}
}
/*
* the upper bound returned by PGM is one passed the end of the
* array. If we are at that point, we should just return "not found"
*/
if (idx == m_reccnt) {
return idx;
}
/*
* We may have walked one passed the actual lower bound, so check
* the index before the current one to see if it is the actual bound
*/
if (m_data[idx].rec.key > key && idx > 0 && m_data[idx-1].rec.key <= key) {
return idx-1;
}
/*
* Otherwise, check idx. If it is a valid bound, then return it,
* otherwise return "not found".
*/
return (m_data[idx].rec.key >= key) ? idx : m_reccnt;
}
private:
Wrapped<R>* m_data;
BloomFilter<R> *m_bf;
size_t m_reccnt;
size_t m_tombstone_cnt;
size_t m_alloc_size;
K m_max_key;
K m_min_key;
pgm::PGMIndex<K, epsilon> m_pgm;
};
}
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