117 lines
3.2 KiB
C++
117 lines
3.2 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
|
|
// This source code is licensed under both the GPLv2 (found in the
|
|
// COPYING file in the root directory) and Apache 2.0 License
|
|
// (found in the LICENSE.Apache file in the root directory).
|
|
//
|
|
#pragma once
|
|
#include <string>
|
|
#include <vector>
|
|
#include "db/dbformat.h"
|
|
#include "rocksdb/slice.h"
|
|
|
|
namespace rocksdb {
|
|
|
|
const std::vector<Slice> empty_operand_list;
|
|
|
|
// The merge context for merging a user key.
|
|
// When doing a Get(), DB will create such a class and pass it when
|
|
// issuing Get() operation to memtables and version_set. The operands
|
|
// will be fetched from the context when issuing partial of full merge.
|
|
class MergeContext {
|
|
public:
|
|
// Clear all the operands
|
|
void Clear() {
|
|
if (operand_list_) {
|
|
operand_list_->clear();
|
|
copied_operands_->clear();
|
|
}
|
|
}
|
|
|
|
// Push a merge operand
|
|
void PushOperand(const Slice& operand_slice, bool operand_pinned = false) {
|
|
Initialize();
|
|
SetDirectionBackward();
|
|
|
|
if (operand_pinned) {
|
|
operand_list_->push_back(operand_slice);
|
|
} else {
|
|
// We need to have our own copy of the operand since it's not pinned
|
|
copied_operands_->emplace_back(
|
|
new std::string(operand_slice.data(), operand_slice.size()));
|
|
operand_list_->push_back(*copied_operands_->back());
|
|
}
|
|
}
|
|
|
|
// Push back a merge operand
|
|
void PushOperandBack(const Slice& operand_slice,
|
|
bool operand_pinned = false) {
|
|
Initialize();
|
|
SetDirectionForward();
|
|
|
|
if (operand_pinned) {
|
|
operand_list_->push_back(operand_slice);
|
|
} else {
|
|
// We need to have our own copy of the operand since it's not pinned
|
|
copied_operands_->emplace_back(
|
|
new std::string(operand_slice.data(), operand_slice.size()));
|
|
operand_list_->push_back(*copied_operands_->back());
|
|
}
|
|
}
|
|
|
|
// return total number of operands in the list
|
|
size_t GetNumOperands() const {
|
|
if (!operand_list_) {
|
|
return 0;
|
|
}
|
|
return operand_list_->size();
|
|
}
|
|
|
|
// Get the operand at the index.
|
|
Slice GetOperand(int index) {
|
|
assert(operand_list_);
|
|
|
|
SetDirectionForward();
|
|
return (*operand_list_)[index];
|
|
}
|
|
|
|
// Return all the operands.
|
|
const std::vector<Slice>& GetOperands() {
|
|
if (!operand_list_) {
|
|
return empty_operand_list;
|
|
}
|
|
|
|
SetDirectionForward();
|
|
return *operand_list_;
|
|
}
|
|
|
|
private:
|
|
void Initialize() {
|
|
if (!operand_list_) {
|
|
operand_list_.reset(new std::vector<Slice>());
|
|
copied_operands_.reset(new std::vector<std::unique_ptr<std::string>>());
|
|
}
|
|
}
|
|
|
|
void SetDirectionForward() {
|
|
if (operands_reversed_ == true) {
|
|
std::reverse(operand_list_->begin(), operand_list_->end());
|
|
operands_reversed_ = false;
|
|
}
|
|
}
|
|
|
|
void SetDirectionBackward() {
|
|
if (operands_reversed_ == false) {
|
|
std::reverse(operand_list_->begin(), operand_list_->end());
|
|
operands_reversed_ = true;
|
|
}
|
|
}
|
|
|
|
// List of operands
|
|
std::unique_ptr<std::vector<Slice>> operand_list_;
|
|
// Copy of operands that are not pinned.
|
|
std::unique_ptr<std::vector<std::unique_ptr<std::string>>> copied_operands_;
|
|
bool operands_reversed_ = true;
|
|
};
|
|
|
|
} // namespace rocksdb
|