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
114 lines
3.1 KiB
C++
114 lines
3.1 KiB
C++
/**
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* @author Deon Nicholas (dnicholas@fb.com)
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* Copyright 2013 Facebook
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*/
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#include "stringappend2.h"
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#include <memory>
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#include <string>
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#include <assert.h>
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#include "rocksdb/slice.h"
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#include "rocksdb/merge_operator.h"
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#include "utilities/merge_operators.h"
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namespace rocksdb {
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// Constructor: also specify the delimiter character.
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StringAppendTESTOperator::StringAppendTESTOperator(char delim_char)
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: delim_(delim_char) {
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}
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// Implementation for the merge operation (concatenates two strings)
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bool StringAppendTESTOperator::FullMerge(
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const Slice& key,
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const Slice* existing_value,
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const std::deque<std::string>& operands,
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std::string* new_value,
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Logger* logger) const {
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// Clear the *new_value for writing.
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assert(new_value);
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new_value->clear();
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// Compute the space needed for the final result.
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int numBytes = 0;
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for(auto it = operands.begin(); it != operands.end(); ++it) {
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numBytes += it->size() + 1; // Plus 1 for the delimiter
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}
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// Only print the delimiter after the first entry has been printed
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bool printDelim = false;
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// Prepend the *existing_value if one exists.
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if (existing_value) {
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new_value->reserve(numBytes + existing_value->size());
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new_value->append(existing_value->data(), existing_value->size());
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printDelim = true;
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} else if (numBytes) {
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new_value->reserve(numBytes-1); // Minus 1 since we have one less delimiter
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}
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// Concatenate the sequence of strings (and add a delimiter between each)
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for(auto it = operands.begin(); it != operands.end(); ++it) {
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if (printDelim) {
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new_value->append(1,delim_);
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}
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new_value->append(*it);
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printDelim = true;
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}
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return true;
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}
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bool StringAppendTESTOperator::PartialMergeMulti(
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const Slice& key, const std::deque<Slice>& operand_list,
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std::string* new_value, Logger* logger) const {
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return false;
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}
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// A version of PartialMerge that actually performs "partial merging".
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// Use this to simulate the exact behaviour of the StringAppendOperator.
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bool StringAppendTESTOperator::_AssocPartialMergeMulti(
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const Slice& key, const std::deque<Slice>& operand_list,
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std::string* new_value, Logger* logger) const {
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// Clear the *new_value for writing
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assert(new_value);
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new_value->clear();
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assert(operand_list.size() >= 2);
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// Generic append
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// Determine and reserve correct size for *new_value.
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size_t size = 0;
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for (const auto& operand : operand_list) {
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size += operand.size();
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}
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size += operand_list.size() - 1; // Delimiters
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new_value->reserve(size);
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// Apply concatenation
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new_value->assign(operand_list.front().data(), operand_list.front().size());
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for (std::deque<Slice>::const_iterator it = operand_list.begin() + 1;
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it != operand_list.end(); ++it) {
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new_value->append(1, delim_);
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new_value->append(it->data(), it->size());
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}
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return true;
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}
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const char* StringAppendTESTOperator::Name() const {
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return "StringAppendTESTOperator";
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}
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std::shared_ptr<MergeOperator>
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MergeOperators::CreateStringAppendTESTOperator() {
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return std::make_shared<StringAppendTESTOperator>(',');
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}
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} // namespace rocksdb
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