cda4006e87
Summary: * PartialMerge api now takes a list of operands instead of two operands. * Add min_pertial_merge_operands to Options, indicating the minimum number of operands to trigger partial merge. * This diff is based on Schalk's previous diff (D14601), but it also includes necessary changes such as updating the pure C api for partial merge. Test Plan: * make check all * develop tests for cases where partial merge takes more than two operands. TODOs (from Schalk): * Add test with min_partial_merge_operands > 2. * Perform benchmarks to measure the performance improvements (can probably use results of task #2837810.) * Add description of problem to doc/index.html. * Change wiki pages to reflect the interface changes. Reviewers: haobo, igor, vamsi Reviewed By: haobo CC: leveldb, dhruba Differential Revision: https://reviews.facebook.net/D16815
70 lines
1.9 KiB
C++
70 lines
1.9 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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#pragma once
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#include "db/dbformat.h"
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#include "rocksdb/slice.h"
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#include <string>
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#include <deque>
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namespace rocksdb {
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const std::deque<std::string> empty_operand_list;
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// The merge context for merging a user key.
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// When doing a Get(), DB will create such a class and pass it when
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// issuing Get() operation to memtables and version_set. The operands
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// will be fetched from the context when issuing partial of full merge.
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class MergeContext {
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public:
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// Clear all the operands
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void Clear() {
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if (operand_list) {
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operand_list->clear();
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}
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}
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// Replace all operands with merge_result, which are expected to be the
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// merge result of them.
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void PushPartialMergeResult(std::string& merge_result) {
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assert (operand_list);
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operand_list->clear();
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operand_list->push_front(std::move(merge_result));
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}
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// Push a merge operand
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void PushOperand(const Slice& operand_slice) {
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Initialize();
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operand_list->push_front(operand_slice.ToString());
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}
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// return total number of operands in the list
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size_t GetNumOperands() const {
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if (!operand_list) {
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return 0;
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}
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return operand_list->size();
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}
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// Get the operand at the index.
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Slice GetOperand(int index) const {
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assert (operand_list);
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return (*operand_list)[index];
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}
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// Return all the operands.
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const std::deque<std::string>& GetOperands() const {
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if (!operand_list) {
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return empty_operand_list;
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}
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return *operand_list;
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}
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private:
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void Initialize() {
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if (!operand_list) {
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operand_list.reset(new std::deque<std::string>());
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}
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}
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std::unique_ptr<std::deque<std::string>> operand_list;
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};
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} // namespace rocksdb
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