rocksdb/db/compaction_iterator.h
Yi Wu 1209b6db5c Blob DB: remove existing garbage collection implementation
Summary:
Red diff to remove existing implementation of garbage collection. The current approach is reference counting kind of approach and require a lot of effort to get the size counter right on compaction and deletion. I'm going to go with a simple mark-sweep kind of approach and will send another PR for that.

CompactionEventListener was added solely for blob db and it adds complexity and overhead to compaction iterator. Removing it as well.
Closes https://github.com/facebook/rocksdb/pull/3551

Differential Revision: D7130190

Pulled By: yiwu-arbug

fbshipit-source-id: c3a375ad2639a3f6ed179df6eda602372cc5b8df
2018-03-02 12:57:23 -08:00

213 lines
8.3 KiB
C++

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <algorithm>
#include <deque>
#include <string>
#include <vector>
#include "db/compaction.h"
#include "db/compaction_iteration_stats.h"
#include "db/merge_helper.h"
#include "db/pinned_iterators_manager.h"
#include "db/range_del_aggregator.h"
#include "db/snapshot_checker.h"
#include "options/cf_options.h"
#include "rocksdb/compaction_filter.h"
namespace rocksdb {
class CompactionIterator {
public:
// A wrapper around Compaction. Has a much smaller interface, only what
// CompactionIterator uses. Tests can override it.
class CompactionProxy {
public:
explicit CompactionProxy(const Compaction* compaction)
: compaction_(compaction) {}
virtual ~CompactionProxy() = default;
virtual int level(size_t compaction_input_level = 0) const {
return compaction_->level();
}
virtual bool KeyNotExistsBeyondOutputLevel(
const Slice& user_key, std::vector<size_t>* level_ptrs) const {
return compaction_->KeyNotExistsBeyondOutputLevel(user_key, level_ptrs);
}
virtual bool bottommost_level() const {
return compaction_->bottommost_level();
}
virtual int number_levels() const { return compaction_->number_levels(); }
virtual Slice GetLargestUserKey() const {
return compaction_->GetLargestUserKey();
}
virtual bool allow_ingest_behind() const {
return compaction_->immutable_cf_options()->allow_ingest_behind;
}
virtual bool preserve_deletes() const {
return compaction_->immutable_cf_options()->preserve_deletes;
}
protected:
CompactionProxy() = default;
private:
const Compaction* compaction_;
};
CompactionIterator(InternalIterator* input, const Comparator* cmp,
MergeHelper* merge_helper, SequenceNumber last_sequence,
std::vector<SequenceNumber>* snapshots,
SequenceNumber earliest_write_conflict_snapshot,
const SnapshotChecker* snapshot_checker, Env* env,
bool expect_valid_internal_key,
RangeDelAggregator* range_del_agg,
const Compaction* compaction = nullptr,
const CompactionFilter* compaction_filter = nullptr,
const std::atomic<bool>* shutting_down = nullptr,
const SequenceNumber preserve_deletes_seqnum = 0);
// Constructor with custom CompactionProxy, used for tests.
CompactionIterator(InternalIterator* input, const Comparator* cmp,
MergeHelper* merge_helper, SequenceNumber last_sequence,
std::vector<SequenceNumber>* snapshots,
SequenceNumber earliest_write_conflict_snapshot,
const SnapshotChecker* snapshot_checker, Env* env,
bool expect_valid_internal_key,
RangeDelAggregator* range_del_agg,
std::unique_ptr<CompactionProxy> compaction,
const CompactionFilter* compaction_filter = nullptr,
const std::atomic<bool>* shutting_down = nullptr,
const SequenceNumber preserve_deletes_seqnum = 0);
~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 CompactionIterationStats& 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();
// Invoke compaction filter if needed.
void InvokeFilterIfNeeded(bool* need_skip, Slice* skip_until);
// 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);
// Checks whether the currently seen ikey_ is needed for
// incremental (differential) snapshot and hence can't be dropped
// or seqnum be zero-ed out even if all other conditions for it are met.
inline bool ikeyNotNeededForIncrementalSnapshot();
InternalIterator* input_;
const Comparator* cmp_;
MergeHelper* merge_helper_;
const std::vector<SequenceNumber>* snapshots_;
const SequenceNumber earliest_write_conflict_snapshot_;
const SnapshotChecker* const snapshot_checker_;
Env* env_;
bool expect_valid_internal_key_;
RangeDelAggregator* range_del_agg_;
std::unique_ptr<CompactionProxy> compaction_;
const CompactionFilter* compaction_filter_;
const std::atomic<bool>* shutting_down_;
const SequenceNumber preserve_deletes_seqnum_;
bool bottommost_level_;
bool valid_ = false;
bool 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_;
InternalKey compaction_filter_skip_until_;
// "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_;
CompactionIterationStats iter_stats_;
// Used to avoid purging uncommitted values. The application can specify
// uncommitted values by providing a SnapshotChecker object.
bool current_key_committed_;
bool IsShuttingDown() {
// This is a best-effort facility, so memory_order_relaxed is sufficient.
return shutting_down_ && shutting_down_->load(std::memory_order_relaxed);
}
};
} // namespace rocksdb