fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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241 lines
8.0 KiB
241 lines
8.0 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include "db/memtable.h"
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#include <memory>
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#include "db/dbformat.h"
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#include "rocksdb/comparator.h"
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#include "rocksdb/env.h"
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#include "rocksdb/iterator.h"
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#include "rocksdb/merge_operator.h"
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#include "util/coding.h"
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#include "util/murmurhash.h"
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namespace leveldb {
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MemTable::MemTable(const InternalKeyComparator& cmp,
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std::shared_ptr<MemTableRepFactory> table_factory,
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int numlevel,
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const Options& options)
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: comparator_(cmp),
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refs_(0),
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arena_impl_(options.arena_block_size),
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table_(table_factory->CreateMemTableRep(comparator_, &arena_impl_)),
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flush_in_progress_(false),
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flush_completed_(false),
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file_number_(0),
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edit_(numlevel),
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first_seqno_(0),
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mem_next_logfile_number_(0),
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mem_logfile_number_(0) { }
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MemTable::~MemTable() {
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assert(refs_ == 0);
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}
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size_t MemTable::ApproximateMemoryUsage() {
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return arena_impl_.ApproximateMemoryUsage() +
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table_->ApproximateMemoryUsage();
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}
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int MemTable::KeyComparator::operator()(const char* aptr, const char* bptr)
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const {
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// Internal keys are encoded as length-prefixed strings.
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Slice a = GetLengthPrefixedSlice(aptr);
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Slice b = GetLengthPrefixedSlice(bptr);
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return comparator.Compare(a, b);
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}
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Slice MemTableRep::UserKey(const char* key) const {
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Slice slice = GetLengthPrefixedSlice(key);
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return Slice(slice.data(), slice.size() - 8);
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}
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// Encode a suitable internal key target for "target" and return it.
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// Uses *scratch as scratch space, and the returned pointer will point
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// into this scratch space.
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static const char* EncodeKey(std::string* scratch, const Slice& target) {
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scratch->clear();
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PutVarint32(scratch, target.size());
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scratch->append(target.data(), target.size());
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return scratch->data();
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}
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class MemTableIterator: public Iterator {
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public:
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explicit MemTableIterator(MemTableRep* table)
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: iter_(table->GetIterator()) { }
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MemTableIterator(MemTableRep* table, const Slice* prefix)
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: iter_(table->GetPrefixIterator(*prefix)) { }
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virtual bool Valid() const { return iter_->Valid(); }
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virtual void Seek(const Slice& k) { iter_->Seek(EncodeKey(&tmp_, k)); }
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virtual void SeekToFirst() { iter_->SeekToFirst(); }
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virtual void SeekToLast() { iter_->SeekToLast(); }
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virtual void Next() { iter_->Next(); }
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virtual void Prev() { iter_->Prev(); }
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virtual Slice key() const {
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return GetLengthPrefixedSlice(iter_->key());
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}
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virtual Slice value() const {
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Slice key_slice = GetLengthPrefixedSlice(iter_->key());
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return GetLengthPrefixedSlice(key_slice.data() + key_slice.size());
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}
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virtual Status status() const { return Status::OK(); }
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private:
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std::shared_ptr<MemTableRep::Iterator> iter_;
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std::string tmp_; // For passing to EncodeKey
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// No copying allowed
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MemTableIterator(const MemTableIterator&);
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void operator=(const MemTableIterator&);
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};
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Iterator* MemTable::NewIterator(const Slice* prefix) {
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if (prefix) {
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return new MemTableIterator(table_.get(), prefix);
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} else {
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return new MemTableIterator(table_.get());
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}
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}
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void MemTable::Add(SequenceNumber s, ValueType type,
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const Slice& key,
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const Slice& value) {
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// Format of an entry is concatenation of:
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// key_size : varint32 of internal_key.size()
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// key bytes : char[internal_key.size()]
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// value_size : varint32 of value.size()
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// value bytes : char[value.size()]
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size_t key_size = key.size();
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size_t val_size = value.size();
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size_t internal_key_size = key_size + 8;
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const size_t encoded_len =
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VarintLength(internal_key_size) + internal_key_size +
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VarintLength(val_size) + val_size;
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char* buf = arena_impl_.Allocate(encoded_len);
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char* p = EncodeVarint32(buf, internal_key_size);
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memcpy(p, key.data(), key_size);
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p += key_size;
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EncodeFixed64(p, (s << 8) | type);
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p += 8;
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p = EncodeVarint32(p, val_size);
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memcpy(p, value.data(), val_size);
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assert((p + val_size) - buf == (unsigned)encoded_len);
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table_->Insert(buf);
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// The first sequence number inserted into the memtable
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assert(first_seqno_ == 0 || s > first_seqno_);
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if (first_seqno_ == 0) {
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first_seqno_ = s;
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}
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}
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bool MemTable::Get(const LookupKey& key, std::string* value, Status* s,
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std::deque<std::string>* operands, const Options& options) {
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Slice memkey = key.memtable_key();
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std::shared_ptr<MemTableRep::Iterator> iter(
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table_->GetIterator(key.user_key()));
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iter->Seek(memkey.data());
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// It is the caller's responsibility to allocate/delete operands list
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assert(operands != nullptr);
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bool merge_in_progress = s->IsMergeInProgress();
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auto merge_operator = options.merge_operator.get();
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auto logger = options.info_log;
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std::string merge_result;
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for (; iter->Valid(); iter->Next()) {
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// entry format is:
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// klength varint32
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// userkey char[klength-8]
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// tag uint64
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// vlength varint32
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// value char[vlength]
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// Check that it belongs to same user key. We do not check the
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// sequence number since the Seek() call above should have skipped
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// all entries with overly large sequence numbers.
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const char* entry = iter->key();
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uint32_t key_length;
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const char* key_ptr = GetVarint32Ptr(entry, entry+5, &key_length);
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if (comparator_.comparator.user_comparator()->Compare(
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Slice(key_ptr, key_length - 8),
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key.user_key()) == 0) {
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// Correct user key
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const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
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switch (static_cast<ValueType>(tag & 0xff)) {
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case kTypeValue: {
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Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
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*s = Status::OK();
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if (merge_in_progress) {
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assert(merge_operator);
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if (!merge_operator->FullMerge(key.user_key(), &v, *operands,
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value, logger.get())) {
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RecordTick(options.statistics, NUMBER_MERGE_FAILURES);
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*s = Status::Corruption("Error: Could not perform merge.");
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}
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} else {
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value->assign(v.data(), v.size());
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}
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return true;
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}
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case kTypeDeletion: {
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if (merge_in_progress) {
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assert(merge_operator);
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*s = Status::OK();
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if (!merge_operator->FullMerge(key.user_key(), nullptr, *operands,
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value, logger.get())) {
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RecordTick(options.statistics, NUMBER_MERGE_FAILURES);
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*s = Status::Corruption("Error: Could not perform merge.");
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}
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} else {
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*s = Status::NotFound(Slice());
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}
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return true;
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}
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case kTypeMerge: {
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Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
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merge_in_progress = true;
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operands->push_front(v.ToString());
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while(operands->size() >= 2) {
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// Attempt to associative merge. (Returns true if successful)
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if (merge_operator->PartialMerge(key.user_key(),
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Slice((*operands)[0]),
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Slice((*operands)[1]),
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&merge_result,
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logger.get())) {
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operands->pop_front();
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swap(operands->front(), merge_result);
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} else {
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// Stack them because user can't associative merge
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break;
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}
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}
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break;
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}
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case kTypeLogData:
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assert(false);
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break;
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}
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} else {
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// exit loop if user key does not match
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break;
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}
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}
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// No change to value, since we have not yet found a Put/Delete
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if (merge_in_progress) {
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*s = Status::MergeInProgress("");
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}
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return false;
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}
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} // namespace leveldb
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