Summary: Move definition and implementation for ArenaWrappedDBIter into its own .h/.cc files. Also, change inlining of functions to better comply with the Google C++ style guide. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5801 Test Plan: make check Differential Revision: D17371012 Pulled By: anand1976 fbshipit-source-id: c1361abc2851575111e357a63d88be3b3d6cb341
325 lines
11 KiB
C++
325 lines
11 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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// 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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#pragma once
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#include <stdint.h>
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#include <string>
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#include "db/db_impl/db_impl.h"
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#include "db/dbformat.h"
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#include "db/range_del_aggregator.h"
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#include "memory/arena.h"
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#include "options/cf_options.h"
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#include "rocksdb/db.h"
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#include "rocksdb/iterator.h"
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#include "table/iterator_wrapper.h"
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#include "util/autovector.h"
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namespace rocksdb {
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// This file declares the factory functions of DBIter, in its original form
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// or a wrapped form with class ArenaWrappedDBIter, which is defined here.
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// Class DBIter, which is declared and implemented inside db_iter.cc, is
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// a iterator that converts internal keys (yielded by an InternalIterator)
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// that were live at the specified sequence number into appropriate user
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// keys.
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// Each internal key is consist of a user key, a sequence number, and a value
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// type. DBIter deals with multiple key versions, tombstones, merge operands,
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// etc, and exposes an Iterator.
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// For example, DBIter may wrap following InternalIterator:
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// user key: AAA value: v3 seqno: 100 type: Put
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// user key: AAA value: v2 seqno: 97 type: Put
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// user key: AAA value: v1 seqno: 95 type: Put
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// user key: BBB value: v1 seqno: 90 type: Put
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// user key: BBC value: N/A seqno: 98 type: Delete
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// user key: BBC value: v1 seqno: 95 type: Put
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// If the snapshot passed in is 102, then the DBIter is expected to
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// expose the following iterator:
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// key: AAA value: v3
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// key: BBB value: v1
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// If the snapshot passed in is 96, then it should expose:
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// key: AAA value: v1
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// key: BBB value: v1
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// key: BBC value: v1
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//
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// Memtables and sstables that make the DB representation contain
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// (userkey,seq,type) => uservalue entries. DBIter
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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 DBIter final: public Iterator {
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public:
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// The following is grossly complicated. TODO: clean it up
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// Which direction is the iterator currently moving?
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// (1) When moving forward:
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// (1a) if current_entry_is_merged_ = false, the internal iterator is
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// positioned at the exact entry that yields this->key(), this->value()
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// (1b) if current_entry_is_merged_ = true, the internal iterator is
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// positioned immediately after the last entry that contributed to the
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// current this->value(). That entry may or may not have key equal to
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// this->key().
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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 Direction {
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kForward,
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kReverse
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};
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// LocalStatistics contain Statistics counters that will be aggregated per
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// each iterator instance and then will be sent to the global statistics when
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// the iterator is destroyed.
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//
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// The purpose of this approach is to avoid perf regression happening
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// when multiple threads bump the atomic counters from a DBIter::Next().
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struct LocalStatistics {
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explicit LocalStatistics() { ResetCounters(); }
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void ResetCounters() {
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next_count_ = 0;
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next_found_count_ = 0;
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prev_count_ = 0;
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prev_found_count_ = 0;
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bytes_read_ = 0;
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skip_count_ = 0;
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}
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void BumpGlobalStatistics(Statistics* global_statistics) {
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RecordTick(global_statistics, NUMBER_DB_NEXT, next_count_);
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RecordTick(global_statistics, NUMBER_DB_NEXT_FOUND, next_found_count_);
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RecordTick(global_statistics, NUMBER_DB_PREV, prev_count_);
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RecordTick(global_statistics, NUMBER_DB_PREV_FOUND, prev_found_count_);
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RecordTick(global_statistics, ITER_BYTES_READ, bytes_read_);
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RecordTick(global_statistics, NUMBER_ITER_SKIP, skip_count_);
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PERF_COUNTER_ADD(iter_read_bytes, bytes_read_);
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ResetCounters();
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}
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// Map to Tickers::NUMBER_DB_NEXT
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uint64_t next_count_;
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// Map to Tickers::NUMBER_DB_NEXT_FOUND
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uint64_t next_found_count_;
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// Map to Tickers::NUMBER_DB_PREV
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uint64_t prev_count_;
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// Map to Tickers::NUMBER_DB_PREV_FOUND
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uint64_t prev_found_count_;
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// Map to Tickers::ITER_BYTES_READ
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uint64_t bytes_read_;
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// Map to Tickers::NUMBER_ITER_SKIP
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uint64_t skip_count_;
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};
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DBIter(Env* _env, const ReadOptions& read_options,
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const ImmutableCFOptions& cf_options,
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const MutableCFOptions& mutable_cf_options, const Comparator* cmp,
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InternalIterator* iter, SequenceNumber s, bool arena_mode,
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uint64_t max_sequential_skip_in_iterations,
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ReadCallback* read_callback, DBImpl* db_impl, ColumnFamilyData* cfd,
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bool allow_blob);
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// No copying allowed
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DBIter(const DBIter&) = delete;
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void operator=(const DBIter&) = delete;
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~DBIter() override {
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// Release pinned data if any
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if (pinned_iters_mgr_.PinningEnabled()) {
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pinned_iters_mgr_.ReleasePinnedData();
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}
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RecordTick(statistics_, NO_ITERATOR_DELETED);
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ResetInternalKeysSkippedCounter();
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local_stats_.BumpGlobalStatistics(statistics_);
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iter_.DeleteIter(arena_mode_);
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}
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virtual void SetIter(InternalIterator* iter) {
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assert(iter_.iter() == nullptr);
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iter_.Set(iter);
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iter_.iter()->SetPinnedItersMgr(&pinned_iters_mgr_);
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}
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virtual ReadRangeDelAggregator* GetRangeDelAggregator() {
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return &range_del_agg_;
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}
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bool Valid() const override { return valid_; }
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Slice key() const override {
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assert(valid_);
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if(start_seqnum_ > 0) {
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return saved_key_.GetInternalKey();
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} else {
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return saved_key_.GetUserKey();
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}
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}
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Slice value() const override {
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assert(valid_);
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if (current_entry_is_merged_) {
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// If pinned_value_ is set then the result of merge operator is one of
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// the merge operands and we should return it.
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return pinned_value_.data() ? pinned_value_ : saved_value_;
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} else if (direction_ == kReverse) {
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return pinned_value_;
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} else {
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return iter_.value();
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}
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}
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Status status() const override {
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if (status_.ok()) {
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return iter_.status();
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} else {
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assert(!valid_);
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return status_;
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}
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}
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bool IsBlob() const {
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assert(valid_ && (allow_blob_ || !is_blob_));
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return is_blob_;
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}
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Status GetProperty(std::string prop_name, std::string* prop) override;
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void Next() final override;
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void Prev() final override;
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void Seek(const Slice& target) final override;
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void SeekForPrev(const Slice& target) final override;
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void SeekToFirst() final override;
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void SeekToLast() final override;
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Env* env() { return env_; }
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void set_sequence(uint64_t s) {
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sequence_ = s;
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if (read_callback_) {
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read_callback_->Refresh(s);
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}
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}
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void set_valid(bool v) { valid_ = v; }
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private:
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// For all methods in this block:
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// PRE: iter_->Valid() && status_.ok()
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// Return false if there was an error, and status() is non-ok, valid_ = false;
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// in this case callers would usually stop what they were doing and return.
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bool ReverseToForward();
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bool ReverseToBackward();
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bool FindValueForCurrentKey();
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bool FindValueForCurrentKeyUsingSeek();
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bool FindUserKeyBeforeSavedKey();
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bool FindNextUserEntry(bool skipping, bool prefix_check);
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bool FindNextUserEntryInternal(bool skipping, bool prefix_check);
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bool ParseKey(ParsedInternalKey* key);
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bool MergeValuesNewToOld();
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void PrevInternal();
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bool TooManyInternalKeysSkipped(bool increment = true);
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bool IsVisible(SequenceNumber sequence);
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// Temporarily pin the blocks that we encounter until ReleaseTempPinnedData()
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// is called
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void TempPinData() {
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if (!pin_thru_lifetime_) {
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pinned_iters_mgr_.StartPinning();
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}
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}
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// Release blocks pinned by TempPinData()
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void ReleaseTempPinnedData() {
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if (!pin_thru_lifetime_ && pinned_iters_mgr_.PinningEnabled()) {
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pinned_iters_mgr_.ReleasePinnedData();
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}
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}
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inline void ClearSavedValue() {
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if (saved_value_.capacity() > 1048576) {
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std::string empty;
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swap(empty, saved_value_);
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} else {
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saved_value_.clear();
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}
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}
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inline void ResetInternalKeysSkippedCounter() {
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local_stats_.skip_count_ += num_internal_keys_skipped_;
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if (valid_) {
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local_stats_.skip_count_--;
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}
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num_internal_keys_skipped_ = 0;
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}
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const SliceTransform* prefix_extractor_;
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Env* const env_;
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Logger* logger_;
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UserComparatorWrapper user_comparator_;
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const MergeOperator* const merge_operator_;
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IteratorWrapper iter_;
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ReadCallback* read_callback_;
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// Max visible sequence number. It is normally the snapshot seq unless we have
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// uncommitted data in db as in WriteUnCommitted.
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SequenceNumber sequence_;
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IterKey saved_key_;
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// Reusable internal key data structure. This is only used inside one function
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// and should not be used across functions. Reusing this object can reduce
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// overhead of calling construction of the function if creating it each time.
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ParsedInternalKey ikey_;
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std::string saved_value_;
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Slice pinned_value_;
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// for prefix seek mode to support prev()
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Statistics* statistics_;
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uint64_t max_skip_;
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uint64_t max_skippable_internal_keys_;
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uint64_t num_internal_keys_skipped_;
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const Slice* iterate_lower_bound_;
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const Slice* iterate_upper_bound_;
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IterKey prefix_start_buf_;
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Status status_;
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Slice prefix_start_key_;
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Direction direction_;
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bool valid_;
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bool current_entry_is_merged_;
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// True if we know that the current entry's seqnum is 0.
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// This information is used as that the next entry will be for another
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// user key.
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bool is_key_seqnum_zero_;
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const bool prefix_same_as_start_;
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// Means that we will pin all data blocks we read as long the Iterator
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// is not deleted, will be true if ReadOptions::pin_data is true
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const bool pin_thru_lifetime_;
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const bool total_order_seek_;
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bool allow_blob_;
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bool is_blob_;
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bool arena_mode_;
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// List of operands for merge operator.
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MergeContext merge_context_;
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ReadRangeDelAggregator range_del_agg_;
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LocalStatistics local_stats_;
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PinnedIteratorsManager pinned_iters_mgr_;
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#ifdef ROCKSDB_LITE
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ROCKSDB_FIELD_UNUSED
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#endif
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DBImpl* db_impl_;
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#ifdef ROCKSDB_LITE
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ROCKSDB_FIELD_UNUSED
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#endif
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ColumnFamilyData* cfd_;
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// for diff snapshots we want the lower bound on the seqnum;
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// if this value > 0 iterator will return internal keys
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SequenceNumber start_seqnum_;
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};
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// Return a new iterator that converts internal keys (yielded by
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// "*internal_iter") that were live at the specified `sequence` number
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// into appropriate user keys.
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extern Iterator* NewDBIterator(
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Env* env, const ReadOptions& read_options,
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const ImmutableCFOptions& cf_options,
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const MutableCFOptions& mutable_cf_options,
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const Comparator* user_key_comparator, InternalIterator* internal_iter,
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const SequenceNumber& sequence, uint64_t max_sequential_skip_in_iterations,
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ReadCallback* read_callback, DBImpl* db_impl = nullptr,
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ColumnFamilyData* cfd = nullptr, bool allow_blob = false);
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} // namespace rocksdb
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