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rocksdb/db/compaction_iterator.h

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// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
#pragma once
#include <algorithm>
#include <deque>
#include <string>
#include <vector>
#include "db/compaction.h"
#include "db/merge_helper.h"
#include "db/pinned_iterators_manager.h"
#include "rocksdb/compaction_filter.h"
#include "util/log_buffer.h"
namespace rocksdb {
struct CompactionIteratorStats {
// Compaction statistics
int64_t num_record_drop_user = 0;
int64_t num_record_drop_hidden = 0;
int64_t num_record_drop_obsolete = 0;
uint64_t total_filter_time = 0;
// Input statistics
// TODO(noetzli): The stats are incomplete. They are lacking everything
// consumed by MergeHelper.
uint64_t num_input_records = 0;
uint64_t num_input_deletion_records = 0;
uint64_t num_input_corrupt_records = 0;
uint64_t total_input_raw_key_bytes = 0;
uint64_t total_input_raw_value_bytes = 0;
};
class CompactionIterator {
public:
CompactionIterator(InternalIterator* input, const Comparator* cmp,
MergeHelper* merge_helper, SequenceNumber last_sequence,
std::vector<SequenceNumber>* snapshots,
SequenceNumber earliest_write_conflict_snapshot, Env* env,
bool expect_valid_internal_key,
const Compaction* compaction = nullptr,
const CompactionFilter* compaction_filter = nullptr,
LogBuffer* log_buffer = nullptr);
~CompactionIterator();
void ResetRecordCounts();
// Seek to the beginning of the compaction iterator output.
//
// REQUIRED: Call only once.
void SeekToFirst();
// Produces the next record in the compaction.
//
// REQUIRED: SeekToFirst() has been called.
void Next();
// Getters
const Slice& key() const { return key_; }
const Slice& value() const { return value_; }
const Status& status() const { return status_; }
const ParsedInternalKey& ikey() const { return ikey_; }
bool Valid() const { return valid_; }
const Slice& user_key() const { return current_user_key_; }
const CompactionIteratorStats& iter_stats() const { return iter_stats_; }
private:
// Processes the input stream to find the next output
void NextFromInput();
// Do last preparations before presenting the output to the callee. At this
// point this only zeroes out the sequence number if possible for better
// compression.
void PrepareOutput();
// Given a sequence number, return the sequence number of the
// earliest snapshot that this sequence number is visible in.
// The snapshots themselves are arranged in ascending order of
// sequence numbers.
// Employ a sequential search because the total number of
// snapshots are typically small.
inline SequenceNumber findEarliestVisibleSnapshot(
SequenceNumber in, SequenceNumber* prev_snapshot);
InternalIterator* input_;
const Comparator* cmp_;
MergeHelper* merge_helper_;
const std::vector<SequenceNumber>* snapshots_;
const SequenceNumber earliest_write_conflict_snapshot_;
Env* env_;
bool expect_valid_internal_key_;
const Compaction* compaction_;
const CompactionFilter* compaction_filter_;
LogBuffer* log_buffer_;
bool bottommost_level_;
bool valid_ = false;
SequenceNumber visible_at_tip_;
SequenceNumber earliest_snapshot_;
SequenceNumber latest_snapshot_;
bool ignore_snapshots_;
// State
//
// Points to a copy of the current compaction iterator output (current_key_)
// if valid_.
Slice key_;
// Points to the value in the underlying iterator that corresponds to the
// current output.
Slice value_;
// The status is OK unless compaction iterator encounters a merge operand
// while not having a merge operator defined.
Status status_;
// Stores the user key, sequence number and type of the current compaction
// iterator output (or current key in the underlying iterator during
// NextFromInput()).
ParsedInternalKey ikey_;
// Stores whether ikey_.user_key is valid. If set to false, the user key is
// not compared against the current key in the underlying iterator.
bool has_current_user_key_ = false;
bool at_next_ = false; // If false, the iterator
// Holds a copy of the current compaction iterator output (or current key in
// the underlying iterator during NextFromInput()).
IterKey current_key_;
Slice current_user_key_;
SequenceNumber current_user_key_sequence_;
SequenceNumber current_user_key_snapshot_;
// True if the iterator has already returned a record for the current key.
bool has_outputted_key_ = false;
// truncated the value of the next key and output it without applying any
// compaction rules. This is used for outputting a put after a single delete.
bool clear_and_output_next_key_ = false;
MergeOutputIterator merge_out_iter_;
// PinnedIteratorsManager used to pin input_ Iterator blocks while reading
// merge operands and then releasing them after consuming them.
PinnedIteratorsManager pinned_iters_mgr_;
std::string compaction_filter_value_;
// "level_ptrs" holds indices that remember which file of an associated
// level we were last checking during the last call to compaction->
// KeyNotExistsBeyondOutputLevel(). This allows future calls to the function
// to pick off where it left off since each subcompaction's key range is
// increasing so a later call to the function must be looking for a key that
// is in or beyond the last file checked during the previous call
std::vector<size_t> level_ptrs_;
CompactionIteratorStats iter_stats_;
};
} // namespace rocksdb