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[RocksDB Performance Branch] Introduce MergeContext to Lazily Initialize merge operand list

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Summary: In get operations, merge_operands is only used in few cases. Lazily initialize it can reduce average latency in some cases

Test Plan: make all check

Reviewers: haobo, kailiu, dhruba

Reviewed By: haobo

CC: igor, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14415
This commit is contained in:
Siying Dong
2013-12-02 18:34:05 -08:00
parent 90729f8b23
commit ef2211a9ca
10 changed files with 129 additions and 53 deletions
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34
db/version_set.cc
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@@ -16,6 +16,7 @@
#include "db/log_reader.h"
#include "db/log_writer.h"
#include "db/memtable.h"
#include "db/merge_context.h"
#include "db/table_cache.h"
#include "rocksdb/env.h"
#include "rocksdb/merge_operator.h"
@@ -287,7 +288,8 @@ struct Saver {
bool* value_found; // Is value set correctly? Used by KeyMayExist
std::string* value;
const MergeOperator* merge_operator;
std::deque<std::string>* merge_operands; // the merge operations encountered
// the merge operations encountered;
MergeContext* merge_context;
Logger* logger;
bool didIO; // did we do any disk io?
Statistics* statistics;
@@ -309,10 +311,10 @@ static void MarkKeyMayExist(void* arg) {
static bool SaveValue(void* arg, const Slice& ikey, const Slice& v, bool didIO){
Saver* s = reinterpret_cast<Saver*>(arg);
std::deque<std::string>* const ops = s->merge_operands; // shorter alias
MergeContext* merge_contex = s->merge_context;
std::string merge_result; // temporary area for merge results later
assert(s != nullptr && ops != nullptr);
assert(s != nullptr && merge_contex != nullptr);
ParsedInternalKey parsed_key;
// TODO: didIO and Merge?
@@ -331,7 +333,8 @@ static bool SaveValue(void* arg, const Slice& ikey, const Slice& v, bool didIO){
} else if (kMerge == s->state) {
assert(s->merge_operator != nullptr);
s->state = kFound;
if (!s->merge_operator->FullMerge(s->user_key, &v, *ops,
if (!s->merge_operator->FullMerge(s->user_key, &v,
merge_contex->GetOperands(),
s->value, s->logger)) {
RecordTick(s->statistics, NUMBER_MERGE_FAILURES);
s->state = kCorrupt;
@@ -346,8 +349,9 @@ static bool SaveValue(void* arg, const Slice& ikey, const Slice& v, bool didIO){
s->state = kDeleted;
} else if (kMerge == s->state) {
s->state = kFound;
if (!s->merge_operator->FullMerge(s->user_key, nullptr, *ops,
s->value, s->logger)) {
if (!s->merge_operator->FullMerge(s->user_key, nullptr,
merge_contex->GetOperands(),
s->value, s->logger)) {
RecordTick(s->statistics, NUMBER_MERGE_FAILURES);
s->state = kCorrupt;
}
@@ -359,16 +363,15 @@ static bool SaveValue(void* arg, const Slice& ikey, const Slice& v, bool didIO){
case kTypeMerge:
assert(s->state == kNotFound || s->state == kMerge);
s->state = kMerge;
ops->push_front(v.ToString());
while (ops->size() >= 2) {
merge_contex->PushOperand(v);
while (merge_contex->GetNumOperands() >= 2) {
// Attempt to merge operands together via user associateive merge
if (s->merge_operator->PartialMerge(s->user_key,
Slice((*ops)[0]),
Slice((*ops)[1]),
merge_contex->GetOperand(0),
merge_contex->GetOperand(1),
&merge_result,
s->logger)) {
ops->pop_front();
swap(ops->front(), merge_result);
merge_contex->PushPartialMergeResult(merge_result);
} else {
// Associative merge returns false ==> stack the operands
break;
@@ -417,7 +420,7 @@ void Version::Get(const ReadOptions& options,
const LookupKey& k,
std::string* value,
Status* status,
std::deque<std::string>* operands,
MergeContext* merge_context,
GetStats* stats,
const Options& db_options,
bool* value_found) {
@@ -436,7 +439,7 @@ void Version::Get(const ReadOptions& options,
saver.value_found = value_found;
saver.value = value;
saver.merge_operator = merge_operator;
saver.merge_operands = operands;
saver.merge_context = merge_context;
saver.logger = logger.get();
saver.didIO = false;
saver.statistics = db_options.statistics.get();
@@ -564,7 +567,8 @@ void Version::Get(const ReadOptions& options,
if (kMerge == saver.state) {
// merge_operands are in saver and we hit the beginning of the key history
// do a final merge of nullptr and operands;
if (merge_operator->FullMerge(user_key, nullptr, *saver.merge_operands,
if (merge_operator->FullMerge(user_key, nullptr,
saver.merge_context->GetOperands(),
value, logger.get())) {
*status = Status::OK();
} else {