rocksdb/db/memtablelist.cc

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
#include "db/memtablelist.h"
#include <string>
#include "rocksdb/db.h"
#include "db/memtable.h"
#include "rocksdb/env.h"
#include "rocksdb/iterator.h"
#include "util/coding.h"
namespace rocksdb {
class InternalKeyComparator;
class Mutex;
class MemTableListIterator;
class VersionSet;
using std::list;
// Increase reference count on all underling memtables
void MemTableList::RefAll() {
for (auto &memtable : memlist_) {
memtable->Ref();
}
}
// Drop reference count on all underling memtables. If the
// refcount of an underlying memtable drops to zero, then
// return it in to_delete vector.
void MemTableList::UnrefAll(std::vector<MemTable*>* to_delete) {
for (auto &memtable : memlist_) {
MemTable* m = memtable->Unref();
if (m != nullptr) {
to_delete->push_back(m);
}
}
}
// Returns the total number of memtables in the list
int MemTableList::size() {
assert(num_flush_not_started_ <= size_);
return size_;
}
// Returns true if there is at least one memtable on which flush has
// not yet started.
bool MemTableList::IsFlushPending(int min_write_buffer_number_to_merge) {
if ((flush_requested_ && num_flush_not_started_ >= 1) ||
(num_flush_not_started_ >= min_write_buffer_number_to_merge)) {
assert(imm_flush_needed.NoBarrier_Load() != nullptr);
return true;
}
return false;
}
// Returns the memtables that need to be flushed.
void MemTableList::PickMemtablesToFlush(std::vector<MemTable*>* ret) {
for (auto it = memlist_.rbegin(); it != memlist_.rend(); it++) {
MemTable* m = *it;
if (!m->flush_in_progress_) {
assert(!m->flush_completed_);
num_flush_not_started_--;
if (num_flush_not_started_ == 0) {
imm_flush_needed.Release_Store(nullptr);
}
m->flush_in_progress_ = true; // flushing will start very soon
ret->push_back(m);
}
}
flush_requested_ = false; // start-flush request is complete
}
// Record a successful flush in the manifest file
Status MemTableList::InstallMemtableFlushResults(
const std::vector<MemTable*> &mems,
VersionSet* vset, Status flushStatus,
port::Mutex* mu, Logger* info_log,
uint64_t file_number,
std::set<uint64_t>& pending_outputs,
std::vector<MemTable*>* to_delete) {
mu->AssertHeld();
// If the flush was not successful, then just reset state.
// Maybe a suceeding attempt to flush will be successful.
if (!flushStatus.ok()) {
for (MemTable* m : mems) {
assert(m->flush_in_progress_);
assert(m->file_number_ == 0);
m->flush_in_progress_ = false;
m->flush_completed_ = false;
m->edit_.Clear();
num_flush_not_started_++;
imm_flush_needed.Release_Store((void *)1);
pending_outputs.erase(file_number);
}
return flushStatus;
}
// flush was sucessful
for (size_t i = 0; i < mems.size(); ++i) {
// All the edits are associated with the first memtable of this batch.
assert(i == 0 || mems[i]->GetEdits()->NumEntries() == 0);
mems[i]->flush_completed_ = true;
mems[i]->file_number_ = file_number;
}
// if some other thread is already commiting, then return
Status s;
if (commit_in_progress_) {
return s;
}
// Only a single thread can be executing this piece of code
commit_in_progress_ = true;
// scan all memtables from the earliest, and commit those
// (in that order) that have finished flushing. Memetables
// are always committed in the order that they were created.
while (!memlist_.empty() && s.ok()) {
MemTable* m = memlist_.back(); // get the last element
if (!m->flush_completed_) {
break;
}
Log(info_log,
"Level-0 commit table #%lu started",
(unsigned long)m->file_number_);
// this can release and reacquire the mutex.
s = vset->LogAndApply(&m->edit_, mu);
// All the later memtables that have the same filenum
// are part of the same batch. They can be committed now.
uint64_t mem_id = 1; // how many memtables has been flushed.
do {
if (s.ok()) { // commit new state
Log(info_log,
"Level-0 commit table #%lu: memtable #%lu done",
(unsigned long)m->file_number_,
(unsigned long)mem_id);
memlist_.remove(m);
assert(m->file_number_ > 0);
// pending_outputs can be cleared only after the newly created file
// has been written to a committed version so that other concurrently
// executing compaction threads do not mistakenly assume that this
// file is not live.
pending_outputs.erase(m->file_number_);
if (m->Unref() != nullptr) {
to_delete->push_back(m);
}
size_--;
} else {
//commit failed. setup state so that we can flush again.
Log(info_log,
"Level-0 commit table #%lu: memtable #%lu failed",
(unsigned long)m->file_number_,
(unsigned long)mem_id);
m->flush_completed_ = false;
m->flush_in_progress_ = false;
m->edit_.Clear();
num_flush_not_started_++;
pending_outputs.erase(m->file_number_);
m->file_number_ = 0;
imm_flush_needed.Release_Store((void *)1);
s = Status::IOError("Unable to commit flushed memtable");
}
++mem_id;
} while (!memlist_.empty() && (m = memlist_.back()) &&
m->file_number_ == file_number);
}
commit_in_progress_ = false;
return s;
}
// New memtables are inserted at the front of the list.
void MemTableList::Add(MemTable* m) {
assert(size_ >= num_flush_not_started_);
size_++;
memlist_.push_front(m);
m->MarkImmutable();
num_flush_not_started_++;
if (num_flush_not_started_ == 1) {
imm_flush_needed.Release_Store((void *)1);
}
}
// Returns an estimate of the number of bytes of data in use.
size_t MemTableList::ApproximateMemoryUsage() {
size_t size = 0;
for (auto &memtable : memlist_) {
size += memtable->ApproximateMemoryUsage();
}
return size;
}
// Search all the memtables starting from the most recent one.
// Return the most recent value found, if any.
[RocksDB] [MergeOperator] The new Merge Interface! Uses merge sequences. Summary: Here are the major changes to the Merge Interface. It has been expanded to handle cases where the MergeOperator is not associative. It does so by stacking up merge operations while scanning through the key history (i.e.: during Get() or Compaction), until a valid Put/Delete/end-of-history is encountered; it then applies all of the merge operations in the correct sequence starting with the base/sentinel value. I have also introduced an "AssociativeMerge" function which allows the user to take advantage of associative merge operations (such as in the case of counters). The implementation will always attempt to merge the operations/operands themselves together when they are encountered, and will resort to the "stacking" method if and only if the "associative-merge" fails. This implementation is conjectured to allow MergeOperator to handle the general case, while still providing the user with the ability to take advantage of certain efficiencies in their own merge-operator / data-structure. NOTE: This is a preliminary diff. This must still go through a lot of review, revision, and testing. Feedback welcome! Test Plan: -This is a preliminary diff. I have only just begun testing/debugging it. -I will be testing this with the existing MergeOperator use-cases and unit-tests (counters, string-append, and redis-lists) -I will be "desk-checking" and walking through the code with the help gdb. -I will find a way of stress-testing the new interface / implementation using db_bench, db_test, merge_test, and/or db_stress. -I will ensure that my tests cover all cases: Get-Memtable, Get-Immutable-Memtable, Get-from-Disk, Iterator-Range-Scan, Flush-Memtable-to-L0, Compaction-L0-L1, Compaction-Ln-L(n+1), Put/Delete found, Put/Delete not-found, end-of-history, end-of-file, etc. -A lot of feedback from the reviewers. Reviewers: haobo, dhruba, zshao, emayanke Reviewed By: haobo CC: leveldb Differential Revision: https://reviews.facebook.net/D11499
2013-08-06 05:14:32 +02:00
// Operands stores the list of merge operations to apply, so far.
bool MemTableList::Get(const LookupKey& key, std::string* value, Status* s,
MergeContext& merge_context, const Options& options) {
for (auto &memtable : memlist_) {
if (memtable->Get(key, value, s, merge_context, options)) {
return true;
}
}
return false;
}
void MemTableList::GetMemTables(std::vector<MemTable*>* output) {
for (auto &memtable : memlist_) {
output->push_back(memtable);
}
}
} // namespace rocksdb