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115 lines
3.2 KiB
115 lines
3.2 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 <iostream>
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#include <fstream>
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#include <thread>
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#include <queue>
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#include "db/unordered_iter.h"
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#include "db/db_impl.h"
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#include "db/dbformat.h"
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#include "db/filename.h"
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#include "leveldb/env.h"
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#include "leveldb/iterator.h"
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#include "port/port.h"
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#include "util/logging.h"
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#include "util/mutexlock.h"
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#include "util/random.h"
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#include "port/port.h"
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namespace leveldb {
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namespace {
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// Memtables and sstables that make the DB representation contain
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// (userkey,seq,type) => uservalue entries. UnorderedIter
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// combines multiple entries for the same userkey found in the DB
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// representation into a single entry while accounting for sequence
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// numbers, deletion markers, overwrites, etc.
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class UnorderedIter : public Iterator {
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public:
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// Which direction is the iterator currently moving?
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// (1) When moving forward, the internal iterator is positioned at
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// the exact entry that yields this->key(), this->value()
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// (2) When moving backwards, the internal iterator is positioned
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// just before all entries whose user key == this->key().
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enum IterPos {Left,Mid,Right};
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UnorderedIter(DBImpl* db, Iterator* iter, Iterator* prefetch_iter,int prefetch_num)
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:
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db_(db),iter_(iter),prefetch_iter_(prefetch_iter),prefetch_num_(prefetch_num) {}
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UnorderedIter(const UnorderedIter&) = delete;
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UnorderedIter& operator=(const UnorderedIter&) = delete;
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~UnorderedIter() override {
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delete iter_;
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}
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bool Valid() const override { return iter_->Valid(); }
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Slice key() const override {
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return iter_->key();
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}
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Slice value() const override {
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buf_for_value=std::move(GetAndParseTrueValue(iter_->value()));
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return Slice(buf_for_value.data(),buf_for_value.size());
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}
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Status status() const override {
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return iter_->status();
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}
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void Next() override;
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void Prev() override;
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void Seek(const Slice& target) override;
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void SeekToFirst() override;
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void SeekToLast() override;
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private:
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std::string GetAndParseTrueValue(Slice tmp_value)const{
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if(tmp_value.size()==0){
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return "";
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}
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if(tmp_value.data()[0]==(char)(0x00)){
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tmp_value.remove_prefix(1);
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return std::string(tmp_value.data(),tmp_value.size());
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}
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tmp_value.remove_prefix(1);
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uint64_t file_id,valuelog_offset;
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bool res=GetVarint64(&tmp_value,&file_id);
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if(!res)assert(0);
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res=GetVarint64(&tmp_value,&valuelog_offset);
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if(!res)assert(0);
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std::string str;
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Status s=db_->ReadValueLog(file_id,valuelog_offset, &str);
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return std::move(str);
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}
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DBImpl* db_;
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Iterator* const iter_;
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};
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void UnorderedIter::Next() {
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iter_->Next();
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}
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void UnorderedIter::Prev() {
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iter_->Prev();
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}
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void UnorderedIter::Seek(const Slice& target) {
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iter_->Seek(target);
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}
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void UnorderedIter::SeekToFirst() {
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iter_->SeekToFirst();
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}
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void UnorderedIter::SeekToLast() {
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iter_->SeekToLast();
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}
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} // anonymous namespace
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Iterator* NewUnorderedIterator(DBImpl* db,Iterator* db_iter) {
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return new UnorderedIter(db,db_iter);
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}
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} // namespace leveldb
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