Summary:
This reverts commit 54d94e9c2c
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The pull request was landed by mistake.
Closes https://github.com/facebook/rocksdb/pull/1755
Differential Revision: D4391678
Pulled By: maysamyabandeh
fbshipit-source-id: 36d5149
415 lines
16 KiB
C++
415 lines
16 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same 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 <atomic>
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#include <deque>
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#include <functional>
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#include <memory>
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#include <string>
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#include <unordered_map>
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#include <vector>
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#include "db/dbformat.h"
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#include "db/memtable_allocator.h"
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#include "db/range_del_aggregator.h"
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#include "db/skiplist.h"
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#include "db/version_edit.h"
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#include "rocksdb/db.h"
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#include "rocksdb/env.h"
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#include "rocksdb/memtablerep.h"
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#include "util/cf_options.h"
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#include "util/concurrent_arena.h"
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#include "util/dynamic_bloom.h"
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#include "util/hash.h"
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#include "util/instrumented_mutex.h"
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namespace rocksdb {
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class Mutex;
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class MemTableIterator;
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class MergeContext;
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class InternalIterator;
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struct MemTableOptions {
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explicit MemTableOptions(
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const ImmutableCFOptions& ioptions,
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const MutableCFOptions& mutable_cf_options);
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size_t write_buffer_size;
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size_t arena_block_size;
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uint32_t memtable_prefix_bloom_bits;
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size_t memtable_huge_page_size;
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bool inplace_update_support;
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size_t inplace_update_num_locks;
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UpdateStatus (*inplace_callback)(char* existing_value,
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uint32_t* existing_value_size,
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Slice delta_value,
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std::string* merged_value);
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size_t max_successive_merges;
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Statistics* statistics;
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MergeOperator* merge_operator;
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Logger* info_log;
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};
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// Batched counters to updated when inserting keys in one write batch.
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// In post process of the write batch, these can be updated together.
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// Only used in concurrent memtable insert case.
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struct MemTablePostProcessInfo {
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uint64_t data_size = 0;
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uint64_t num_entries = 0;
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uint64_t num_deletes = 0;
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};
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// Note: Many of the methods in this class have comments indicating that
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// external synchromization is required as these methods are not thread-safe.
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// It is up to higher layers of code to decide how to prevent concurrent
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// invokation of these methods. This is usually done by acquiring either
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// the db mutex or the single writer thread.
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//
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// Some of these methods are documented to only require external
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// synchronization if this memtable is immutable. Calling MarkImmutable() is
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// not sufficient to guarantee immutability. It is up to higher layers of
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// code to determine if this MemTable can still be modified by other threads.
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// Eg: The Superversion stores a pointer to the current MemTable (that can
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// be modified) and a separate list of the MemTables that can no longer be
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// written to (aka the 'immutable memtables').
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class MemTable {
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public:
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struct KeyComparator : public MemTableRep::KeyComparator {
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const InternalKeyComparator comparator;
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explicit KeyComparator(const InternalKeyComparator& c) : comparator(c) { }
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virtual int operator()(const char* prefix_len_key1,
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const char* prefix_len_key2) const override;
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virtual int operator()(const char* prefix_len_key,
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const Slice& key) const override;
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};
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// MemTables are reference counted. The initial reference count
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// is zero and the caller must call Ref() at least once.
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//
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// earliest_seq should be the current SequenceNumber in the db such that any
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// key inserted into this memtable will have an equal or larger seq number.
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// (When a db is first created, the earliest sequence number will be 0).
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// If the earliest sequence number is not known, kMaxSequenceNumber may be
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// used, but this may prevent some transactions from succeeding until the
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// first key is inserted into the memtable.
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explicit MemTable(const InternalKeyComparator& comparator,
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const ImmutableCFOptions& ioptions,
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const MutableCFOptions& mutable_cf_options,
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WriteBufferManager* write_buffer_manager,
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SequenceNumber earliest_seq);
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// Do not delete this MemTable unless Unref() indicates it not in use.
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~MemTable();
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// Increase reference count.
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable.
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void Ref() { ++refs_; }
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// Drop reference count.
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// If the refcount goes to zero return this memtable, otherwise return null.
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable.
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MemTable* Unref() {
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--refs_;
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assert(refs_ >= 0);
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if (refs_ <= 0) {
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return this;
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}
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return nullptr;
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}
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// Returns an estimate of the number of bytes of data in use by this
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// data structure.
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//
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable (unless this Memtable is immutable).
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size_t ApproximateMemoryUsage();
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// This method heuristically determines if the memtable should continue to
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// host more data.
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bool ShouldScheduleFlush() const {
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return flush_state_.load(std::memory_order_relaxed) == FLUSH_REQUESTED;
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}
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// Returns true if a flush should be scheduled and the caller should
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// be the one to schedule it
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bool MarkFlushScheduled() {
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auto before = FLUSH_REQUESTED;
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return flush_state_.compare_exchange_strong(before, FLUSH_SCHEDULED,
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std::memory_order_relaxed,
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std::memory_order_relaxed);
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}
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// Return an iterator that yields the contents of the memtable.
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//
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// The caller must ensure that the underlying MemTable remains live
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// while the returned iterator is live. The keys returned by this
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// iterator are internal keys encoded by AppendInternalKey in the
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// db/dbformat.{h,cc} module.
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//
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// By default, it returns an iterator for prefix seek if prefix_extractor
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// is configured in Options.
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// arena: If not null, the arena needs to be used to allocate the Iterator.
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// Calling ~Iterator of the iterator will destroy all the states but
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// those allocated in arena.
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InternalIterator* NewIterator(const ReadOptions& read_options, Arena* arena);
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InternalIterator* NewRangeTombstoneIterator(const ReadOptions& read_options);
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// Add an entry into memtable that maps key to value at the
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// specified sequence number and with the specified type.
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// Typically value will be empty if type==kTypeDeletion.
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//
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// REQUIRES: if allow_concurrent = false, external synchronization to prevent
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// simultaneous operations on the same MemTable.
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void Add(SequenceNumber seq, ValueType type, const Slice& key,
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const Slice& value, bool allow_concurrent = false,
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MemTablePostProcessInfo* post_process_info = nullptr);
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// If memtable contains a value for key, store it in *value and return true.
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// If memtable contains a deletion for key, store a NotFound() error
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// in *status and return true.
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// If memtable contains Merge operation as the most recent entry for a key,
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// and the merge process does not stop (not reaching a value or delete),
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// prepend the current merge operand to *operands.
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// store MergeInProgress in s, and return false.
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// Else, return false.
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// If any operation was found, its most recent sequence number
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// will be stored in *seq on success (regardless of whether true/false is
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// returned). Otherwise, *seq will be set to kMaxSequenceNumber.
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// On success, *s may be set to OK, NotFound, or MergeInProgress. Any other
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// status returned indicates a corruption or other unexpected error.
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bool Get(const LookupKey& key, std::string* value, Status* s,
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MergeContext* merge_context, RangeDelAggregator* range_del_agg,
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SequenceNumber* seq, const ReadOptions& read_opts);
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bool Get(const LookupKey& key, std::string* value, Status* s,
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MergeContext* merge_context, RangeDelAggregator* range_del_agg,
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const ReadOptions& read_opts) {
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SequenceNumber seq;
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return Get(key, value, s, merge_context, range_del_agg, &seq, read_opts);
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}
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// Attempts to update the new_value inplace, else does normal Add
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// Pseudocode
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// if key exists in current memtable && prev_value is of type kTypeValue
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// if new sizeof(new_value) <= sizeof(prev_value)
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// update inplace
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// else add(key, new_value)
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// else add(key, new_value)
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//
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable.
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void Update(SequenceNumber seq,
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const Slice& key,
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const Slice& value);
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// If prev_value for key exists, attempts to update it inplace.
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// else returns false
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// Pseudocode
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// if key exists in current memtable && prev_value is of type kTypeValue
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// new_value = delta(prev_value)
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// if sizeof(new_value) <= sizeof(prev_value)
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// update inplace
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// else add(key, new_value)
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// else return false
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//
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable.
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bool UpdateCallback(SequenceNumber seq,
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const Slice& key,
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const Slice& delta);
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// Returns the number of successive merge entries starting from the newest
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// entry for the key up to the last non-merge entry or last entry for the
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// key in the memtable.
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size_t CountSuccessiveMergeEntries(const LookupKey& key);
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// Update counters and flush status after inserting a whole write batch
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// Used in concurrent memtable inserts.
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void BatchPostProcess(const MemTablePostProcessInfo& update_counters) {
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num_entries_.fetch_add(update_counters.num_entries,
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std::memory_order_relaxed);
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data_size_.fetch_add(update_counters.data_size, std::memory_order_relaxed);
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if (update_counters.num_deletes != 0) {
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num_deletes_.fetch_add(update_counters.num_deletes,
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std::memory_order_relaxed);
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}
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UpdateFlushState();
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}
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// Get total number of entries in the mem table.
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable (unless this Memtable is immutable).
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uint64_t num_entries() const {
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return num_entries_.load(std::memory_order_relaxed);
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}
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// Get total number of deletes in the mem table.
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable (unless this Memtable is immutable).
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uint64_t num_deletes() const {
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return num_deletes_.load(std::memory_order_relaxed);
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}
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// Returns the edits area that is needed for flushing the memtable
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VersionEdit* GetEdits() { return &edit_; }
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// Returns if there is no entry inserted to the mem table.
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable (unless this Memtable is immutable).
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bool IsEmpty() const { return first_seqno_ == 0; }
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// Returns the sequence number of the first element that was inserted
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// into the memtable.
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable (unless this Memtable is immutable).
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SequenceNumber GetFirstSequenceNumber() {
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return first_seqno_.load(std::memory_order_relaxed);
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}
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// Returns the sequence number that is guaranteed to be smaller than or equal
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// to the sequence number of any key that could be inserted into this
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// memtable. It can then be assumed that any write with a larger(or equal)
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// sequence number will be present in this memtable or a later memtable.
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//
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// If the earliest sequence number could not be determined,
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// kMaxSequenceNumber will be returned.
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SequenceNumber GetEarliestSequenceNumber() {
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return earliest_seqno_.load(std::memory_order_relaxed);
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}
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// Returns the next active logfile number when this memtable is about to
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// be flushed to storage
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable.
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uint64_t GetNextLogNumber() { return mem_next_logfile_number_; }
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// Sets the next active logfile number when this memtable is about to
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// be flushed to storage
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable.
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void SetNextLogNumber(uint64_t num) { mem_next_logfile_number_ = num; }
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// if this memtable contains data from a committed
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// two phase transaction we must take note of the
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// log which contains that data so we can know
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// when to relese that log
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void RefLogContainingPrepSection(uint64_t log);
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uint64_t GetMinLogContainingPrepSection();
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// Notify the underlying storage that no more items will be added.
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// REQUIRES: external synchronization to prevent simultaneous
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// operations on the same MemTable.
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// After MarkImmutable() is called, you should not attempt to
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// write anything to this MemTable(). (Ie. do not call Add() or Update()).
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void MarkImmutable() {
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table_->MarkReadOnly();
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allocator_.DoneAllocating();
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}
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// return true if the current MemTableRep supports merge operator.
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bool IsMergeOperatorSupported() const {
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return table_->IsMergeOperatorSupported();
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}
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// return true if the current MemTableRep supports snapshots.
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// inplace update prevents snapshots,
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bool IsSnapshotSupported() const {
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return table_->IsSnapshotSupported() && !moptions_.inplace_update_support;
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}
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uint64_t ApproximateSize(const Slice& start_ikey, const Slice& end_ikey);
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// Get the lock associated for the key
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port::RWMutex* GetLock(const Slice& key);
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const InternalKeyComparator& GetInternalKeyComparator() const {
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return comparator_.comparator;
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}
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const MemTableOptions* GetMemTableOptions() const { return &moptions_; }
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private:
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enum FlushStateEnum { FLUSH_NOT_REQUESTED, FLUSH_REQUESTED, FLUSH_SCHEDULED };
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friend class MemTableIterator;
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friend class MemTableBackwardIterator;
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friend class MemTableList;
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KeyComparator comparator_;
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const MemTableOptions moptions_;
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int refs_;
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const size_t kArenaBlockSize;
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ConcurrentArena arena_;
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MemTableAllocator allocator_;
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unique_ptr<MemTableRep> table_;
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unique_ptr<MemTableRep> range_del_table_;
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bool is_range_del_table_empty_;
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// Total data size of all data inserted
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std::atomic<uint64_t> data_size_;
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std::atomic<uint64_t> num_entries_;
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std::atomic<uint64_t> num_deletes_;
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// These are used to manage memtable flushes to storage
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bool flush_in_progress_; // started the flush
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bool flush_completed_; // finished the flush
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uint64_t file_number_; // filled up after flush is complete
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// The updates to be applied to the transaction log when this
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// memtable is flushed to storage.
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VersionEdit edit_;
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// The sequence number of the kv that was inserted first
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std::atomic<SequenceNumber> first_seqno_;
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// The db sequence number at the time of creation or kMaxSequenceNumber
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// if not set.
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std::atomic<SequenceNumber> earliest_seqno_;
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// The log files earlier than this number can be deleted.
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uint64_t mem_next_logfile_number_;
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// the earliest log containing a prepared section
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// which has been inserted into this memtable.
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std::atomic<uint64_t> min_prep_log_referenced_;
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// rw locks for inplace updates
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std::vector<port::RWMutex> locks_;
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const SliceTransform* const prefix_extractor_;
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std::unique_ptr<DynamicBloom> prefix_bloom_;
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std::atomic<FlushStateEnum> flush_state_;
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Env* env_;
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// Extract sequential insert prefixes.
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const SliceTransform* insert_with_hint_prefix_extractor_;
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// Insert hints for each prefix.
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std::unordered_map<Slice, void*, SliceHasher> insert_hints_;
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// Returns a heuristic flush decision
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bool ShouldFlushNow() const;
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// Updates flush_state_ using ShouldFlushNow()
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void UpdateFlushState();
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// No copying allowed
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MemTable(const MemTable&);
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MemTable& operator=(const MemTable&);
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};
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extern const char* EncodeKey(std::string* scratch, const Slice& target);
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} // namespace rocksdb
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