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rocksdb/db/dbformat.h

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// 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).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// 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.
#pragma once
#include <stdio.h>
#include <string>
#include <utility>
#include "monitoring/perf_context_imp.h"
#include "rocksdb/comparator.h"
#include "rocksdb/db.h"
#include "rocksdb/filter_policy.h"
#include "rocksdb/slice.h"
#include "rocksdb/slice_transform.h"
#include "rocksdb/table.h"
#include "rocksdb/types.h"
#include "util/coding.h"
#include "util/logging.h"
namespace rocksdb {
class InternalKey;
// Value types encoded as the last component of internal keys.
// DO NOT CHANGE THESE ENUM VALUES: they are embedded in the on-disk
// data structures.
// The highest bit of the value type needs to be reserved to SST tables
// for them to do more flexible encoding.
enum ValueType : unsigned char {
kTypeDeletion = 0x0,
kTypeValue = 0x1,
kTypeMerge = 0x2,
kTypeLogData = 0x3, // WAL only.
kTypeColumnFamilyDeletion = 0x4, // WAL only.
kTypeColumnFamilyValue = 0x5, // WAL only.
kTypeColumnFamilyMerge = 0x6, // WAL only.
kTypeSingleDeletion = 0x7,
kTypeColumnFamilySingleDeletion = 0x8, // WAL only.
kTypeBeginPrepareXID = 0x9, // WAL only.
kTypeEndPrepareXID = 0xA, // WAL only.
kTypeCommitXID = 0xB, // WAL only.
kTypeRollbackXID = 0xC, // WAL only.
kTypeNoop = 0xD, // WAL only.
kTypeColumnFamilyRangeDeletion = 0xE, // WAL only.
kTypeRangeDeletion = 0xF, // meta block
kTypeColumnFamilyBlobIndex = 0x10, // Blob DB only
kTypeBlobIndex = 0x11, // Blob DB only
// When the prepared record is also persisted in db, we use a different
// record. This is to ensure that the WAL that is generated by a WritePolicy
// is not mistakenly read by another, which would result into data
// inconsistency.
kTypeBeginPersistedPrepareXID = 0x12, // WAL only.
// Similar to kTypeBeginPersistedPrepareXID, this is to ensure that WAL
// generated by WriteUnprepared write policy is not mistakenly read by
// another.
kTypeBeginUnprepareXID = 0x13, // WAL only.
kMaxValue = 0x7F // Not used for storing records.
};
// Defined in dbformat.cc
extern const ValueType kValueTypeForSeek;
extern const ValueType kValueTypeForSeekForPrev;
// Checks whether a type is an inline value type
// (i.e. a type used in memtable skiplist and sst file datablock).
inline bool IsValueType(ValueType t) {
return t <= kTypeMerge || t == kTypeSingleDeletion || t == kTypeBlobIndex;
}
// Checks whether a type is from user operation
// kTypeRangeDeletion is in meta block so this API is separated from above
inline bool IsExtendedValueType(ValueType t) {
return IsValueType(t) || t == kTypeRangeDeletion;
}
// We leave eight bits empty at the bottom so a type and sequence#
// can be packed together into 64-bits.
static const SequenceNumber kMaxSequenceNumber =
((0x1ull << 56) - 1);
static const SequenceNumber kDisableGlobalSequenceNumber = port::kMaxUint64;
struct ParsedInternalKey {
Slice user_key;
SequenceNumber sequence;
ValueType type;
ParsedInternalKey()
: sequence(kMaxSequenceNumber) // Make code analyzer happy
{} // Intentionally left uninitialized (for speed)
ParsedInternalKey(const Slice& u, const SequenceNumber& seq, ValueType t)
: user_key(u), sequence(seq), type(t) { }
std::string DebugString(bool hex = false) const;
void clear() {
user_key.clear();
sequence = 0;
type = kTypeDeletion;
}
};
// Return the length of the encoding of "key".
inline size_t InternalKeyEncodingLength(const ParsedInternalKey& key) {
return key.user_key.size() + 8;
}
// Pack a sequence number and a ValueType into a uint64_t
extern uint64_t PackSequenceAndType(uint64_t seq, ValueType t);
// Given the result of PackSequenceAndType, store the sequence number in *seq
// and the ValueType in *t.
extern void UnPackSequenceAndType(uint64_t packed, uint64_t* seq, ValueType* t);
EntryType GetEntryType(ValueType value_type);
// Append the serialization of "key" to *result.
extern void AppendInternalKey(std::string* result,
const ParsedInternalKey& key);
// Serialized internal key consists of user key followed by footer.
// This function appends the footer to *result, assuming that *result already
// contains the user key at the end.
extern void AppendInternalKeyFooter(std::string* result, SequenceNumber s,
ValueType t);
// Attempt to parse an internal key from "internal_key". On success,
// stores the parsed data in "*result", and returns true.
//
// On error, returns false, leaves "*result" in an undefined state.
extern bool ParseInternalKey(const Slice& internal_key,
ParsedInternalKey* result);
// Returns the user key portion of an internal key.
inline Slice ExtractUserKey(const Slice& internal_key) {
assert(internal_key.size() >= 8);
return Slice(internal_key.data(), internal_key.size() - 8);
}
inline ValueType ExtractValueType(const Slice& internal_key) {
assert(internal_key.size() >= 8);
const size_t n = internal_key.size();
uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
unsigned char c = num & 0xff;
return static_cast<ValueType>(c);
}
// A comparator for internal keys that uses a specified comparator for
// the user key portion and breaks ties by decreasing sequence number.
class InternalKeyComparator
#ifdef NDEBUG
final
#endif
: public Comparator {
private:
const Comparator* user_comparator_;
std::string name_;
public:
explicit InternalKeyComparator(const Comparator* c) : user_comparator_(c),
name_("rocksdb.InternalKeyComparator:" +
std::string(user_comparator_->Name())) {
}
virtual ~InternalKeyComparator() {}
virtual const char* Name() const override;
virtual int Compare(const Slice& a, const Slice& b) const override;
// Same as Compare except that it excludes the value type from comparison
virtual int CompareKeySeq(const Slice& a, const Slice& b) const;
virtual void FindShortestSeparator(std::string* start,
const Slice& limit) const override;
virtual void FindShortSuccessor(std::string* key) const override;
const Comparator* user_comparator() const { return user_comparator_; }
int Compare(const InternalKey& a, const InternalKey& b) const;
int Compare(const ParsedInternalKey& a, const ParsedInternalKey& b) const;
virtual const Comparator* GetRootComparator() const override {
return user_comparator_->GetRootComparator();
}
};
// Modules in this directory should keep internal keys wrapped inside
// the following class instead of plain strings so that we do not
// incorrectly use string comparisons instead of an InternalKeyComparator.
class InternalKey {
private:
std::string rep_;
public:
InternalKey() { } // Leave rep_ as empty to indicate it is invalid
InternalKey(const Slice& _user_key, SequenceNumber s, ValueType t) {
AppendInternalKey(&rep_, ParsedInternalKey(_user_key, s, t));
}
// sets the internal key to be bigger or equal to all internal keys with this
// user key
void SetMaxPossibleForUserKey(const Slice& _user_key) {
AppendInternalKey(
&rep_, ParsedInternalKey(_user_key, 0, static_cast<ValueType>(0)));
}
// sets the internal key to be smaller or equal to all internal keys with this
// user key
void SetMinPossibleForUserKey(const Slice& _user_key) {
AppendInternalKey(&rep_, ParsedInternalKey(_user_key, kMaxSequenceNumber,
kValueTypeForSeek));
}
bool Valid() const {
ParsedInternalKey parsed;
return ParseInternalKey(Slice(rep_), &parsed);
}
void DecodeFrom(const Slice& s) { rep_.assign(s.data(), s.size()); }
Slice Encode() const {
assert(!rep_.empty());
return rep_;
}
Slice user_key() const { return ExtractUserKey(rep_); }
size_t size() { return rep_.size(); }
void Set(const Slice& _user_key, SequenceNumber s, ValueType t) {
SetFrom(ParsedInternalKey(_user_key, s, t));
}
void SetFrom(const ParsedInternalKey& p) {
rep_.clear();
AppendInternalKey(&rep_, p);
}
void Clear() { rep_.clear(); }
// The underlying representation.
// Intended only to be used together with ConvertFromUserKey().
std::string* rep() { return &rep_; }
// Assuming that *rep() contains a user key, this method makes internal key
// out of it in-place. This saves a memcpy compared to Set()/SetFrom().
void ConvertFromUserKey(SequenceNumber s, ValueType t) {
AppendInternalKeyFooter(&rep_, s, t);
}
std::string DebugString(bool hex = false) const;
};
inline int InternalKeyComparator::Compare(
const InternalKey& a, const InternalKey& b) const {
return Compare(a.Encode(), b.Encode());
}
inline bool ParseInternalKey(const Slice& internal_key,
ParsedInternalKey* result) {
const size_t n = internal_key.size();
if (n < 8) return false;
uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
unsigned char c = num & 0xff;
result->sequence = num >> 8;
result->type = static_cast<ValueType>(c);
assert(result->type <= ValueType::kMaxValue);
result->user_key = Slice(internal_key.data(), n - 8);
return IsExtendedValueType(result->type);
}
// Update the sequence number in the internal key.
// Guarantees not to invalidate ikey.data().
inline void UpdateInternalKey(std::string* ikey, uint64_t seq, ValueType t) {
size_t ikey_sz = ikey->size();
assert(ikey_sz >= 8);
uint64_t newval = (seq << 8) | t;
// Note: Since C++11, strings are guaranteed to be stored contiguously and
// string::operator[]() is guaranteed not to change ikey.data().
EncodeFixed64(&(*ikey)[ikey_sz - 8], newval);
}
// Get the sequence number from the internal key
inline uint64_t GetInternalKeySeqno(const Slice& internal_key) {
const size_t n = internal_key.size();
assert(n >= 8);
uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
return num >> 8;
}
// A helper class useful for DBImpl::Get()
class LookupKey {
public:
// Initialize *this for looking up user_key at a snapshot with
// the specified sequence number.
LookupKey(const Slice& _user_key, SequenceNumber sequence);
~LookupKey();
// Return a key suitable for lookup in a MemTable.
Slice memtable_key() const {
return Slice(start_, static_cast<size_t>(end_ - start_));
}
// Return an internal key (suitable for passing to an internal iterator)
Slice internal_key() const {
return Slice(kstart_, static_cast<size_t>(end_ - kstart_));
}
// Return the user key
Slice user_key() const {
return Slice(kstart_, static_cast<size_t>(end_ - kstart_ - 8));
}
private:
// We construct a char array of the form:
// klength varint32 <-- start_
// userkey char[klength] <-- kstart_
// tag uint64
// <-- end_
// The array is a suitable MemTable key.
// The suffix starting with "userkey" can be used as an InternalKey.
const char* start_;
const char* kstart_;
const char* end_;
char space_[200]; // Avoid allocation for short keys
// No copying allowed
LookupKey(const LookupKey&);
void operator=(const LookupKey&);
};
inline LookupKey::~LookupKey() {
if (start_ != space_) delete[] start_;
}
class IterKey {
public:
IterKey()
: buf_(space_),
buf_size_(sizeof(space_)),
key_(buf_),
key_size_(0),
is_user_key_(true) {}
~IterKey() { ResetBuffer(); }
Slice GetInternalKey() const {
assert(!IsUserKey());
return Slice(key_, key_size_);
}
Slice GetUserKey() const {
if (IsUserKey()) {
return Slice(key_, key_size_);
} else {
assert(key_size_ >= 8);
return Slice(key_, key_size_ - 8);
}
}
size_t Size() const { return key_size_; }
void Clear() { key_size_ = 0; }
// Append "non_shared_data" to its back, from "shared_len"
// This function is used in Block::Iter::ParseNextKey
// shared_len: bytes in [0, shard_len-1] would be remained
// non_shared_data: data to be append, its length must be >= non_shared_len
void TrimAppend(const size_t shared_len, const char* non_shared_data,
const size_t non_shared_len) {
assert(shared_len <= key_size_);
size_t total_size = shared_len + non_shared_len;
if (IsKeyPinned() /* key is not in buf_ */) {
// Copy the key from external memory to buf_ (copy shared_len bytes)
EnlargeBufferIfNeeded(total_size);
memcpy(buf_, key_, shared_len);
} else if (total_size > buf_size_) {
// Need to allocate space, delete previous space
char* p = new char[total_size];
memcpy(p, key_, shared_len);
if (buf_ != space_) {
delete[] buf_;
}
buf_ = p;
buf_size_ = total_size;
}
memcpy(buf_ + shared_len, non_shared_data, non_shared_len);
key_ = buf_;
key_size_ = total_size;
}
Slice SetUserKey(const Slice& key, bool copy = true) {
is_user_key_ = true;
return SetKeyImpl(key, copy);
}
Slice SetInternalKey(const Slice& key, bool copy = true) {
is_user_key_ = false;
return SetKeyImpl(key, copy);
}
// Copies the content of key, updates the reference to the user key in ikey
// and returns a Slice referencing the new copy.
Slice SetInternalKey(const Slice& key, ParsedInternalKey* ikey) {
size_t key_n = key.size();
assert(key_n >= 8);
SetInternalKey(key);
ikey->user_key = Slice(key_, key_n - 8);
return Slice(key_, key_n);
}
// Copy the key into IterKey own buf_
void OwnKey() {
assert(IsKeyPinned() == true);
Reserve(key_size_);
memcpy(buf_, key_, key_size_);
key_ = buf_;
}
// Update the sequence number in the internal key. Guarantees not to
// invalidate slices to the key (and the user key).
void UpdateInternalKey(uint64_t seq, ValueType t) {
assert(!IsKeyPinned());
assert(key_size_ >= 8);
uint64_t newval = (seq << 8) | t;
EncodeFixed64(&buf_[key_size_ - 8], newval);
}
bool IsKeyPinned() const { return (key_ != buf_); }
void SetInternalKey(const Slice& key_prefix, const Slice& user_key,
SequenceNumber s,
ValueType value_type = kValueTypeForSeek) {
size_t psize = key_prefix.size();
size_t usize = user_key.size();
EnlargeBufferIfNeeded(psize + usize + sizeof(uint64_t));
if (psize > 0) {
memcpy(buf_, key_prefix.data(), psize);
}
memcpy(buf_ + psize, user_key.data(), usize);
EncodeFixed64(buf_ + usize + psize, PackSequenceAndType(s, value_type));
key_ = buf_;
key_size_ = psize + usize + sizeof(uint64_t);
is_user_key_ = false;
}
void SetInternalKey(const Slice& user_key, SequenceNumber s,
ValueType value_type = kValueTypeForSeek) {
SetInternalKey(Slice(), user_key, s, value_type);
}
void Reserve(size_t size) {
EnlargeBufferIfNeeded(size);
key_size_ = size;
}
void SetInternalKey(const ParsedInternalKey& parsed_key) {
SetInternalKey(Slice(), parsed_key);
}
void SetInternalKey(const Slice& key_prefix,
const ParsedInternalKey& parsed_key_suffix) {
SetInternalKey(key_prefix, parsed_key_suffix.user_key,
parsed_key_suffix.sequence, parsed_key_suffix.type);
}
void EncodeLengthPrefixedKey(const Slice& key) {
auto size = key.size();
EnlargeBufferIfNeeded(size + static_cast<size_t>(VarintLength(size)));
char* ptr = EncodeVarint32(buf_, static_cast<uint32_t>(size));
memcpy(ptr, key.data(), size);
key_ = buf_;
is_user_key_ = true;
}
bool IsUserKey() const { return is_user_key_; }
private:
char* buf_;
size_t buf_size_;
const char* key_;
size_t key_size_;
char space_[32]; // Avoid allocation for short keys
bool is_user_key_;
Slice SetKeyImpl(const Slice& key, bool copy) {
size_t size = key.size();
if (copy) {
// Copy key to buf_
EnlargeBufferIfNeeded(size);
memcpy(buf_, key.data(), size);
key_ = buf_;
} else {
// Update key_ to point to external memory
key_ = key.data();
}
key_size_ = size;
return Slice(key_, key_size_);
}
void ResetBuffer() {
if (buf_ != space_) {
delete[] buf_;
buf_ = space_;
}
buf_size_ = sizeof(space_);
key_size_ = 0;
}
// Enlarge the buffer size if needed based on key_size.
// By default, static allocated buffer is used. Once there is a key
// larger than the static allocated buffer, another buffer is dynamically
// allocated, until a larger key buffer is requested. In that case, we
// reallocate buffer and delete the old one.
void EnlargeBufferIfNeeded(size_t key_size) {
// If size is smaller than buffer size, continue using current buffer,
// or the static allocated one, as default
if (key_size > buf_size_) {
EnlargeBuffer(key_size);
}
}
void EnlargeBuffer(size_t key_size);
// No copying allowed
IterKey(const IterKey&) = delete;
void operator=(const IterKey&) = delete;
};
class InternalKeySliceTransform : public SliceTransform {
public:
explicit InternalKeySliceTransform(const SliceTransform* transform)
: transform_(transform) {}
virtual const char* Name() const override { return transform_->Name(); }
virtual Slice Transform(const Slice& src) const override {
auto user_key = ExtractUserKey(src);
return transform_->Transform(user_key);
}
virtual bool InDomain(const Slice& src) const override {
auto user_key = ExtractUserKey(src);
return transform_->InDomain(user_key);
}
virtual bool InRange(const Slice& dst) const override {
auto user_key = ExtractUserKey(dst);
return transform_->InRange(user_key);
}
const SliceTransform* user_prefix_extractor() const { return transform_; }
private:
// Like comparator, InternalKeySliceTransform will not take care of the
// deletion of transform_
const SliceTransform* const transform_;
};
// Read the key of a record from a write batch.
// if this record represent the default column family then cf_record
// must be passed as false, otherwise it must be passed as true.
extern bool ReadKeyFromWriteBatchEntry(Slice* input, Slice* key,
bool cf_record);
// Read record from a write batch piece from input.
// tag, column_family, key, value and blob are return values. Callers own the
// Slice they point to.
// Tag is defined as ValueType.
// input will be advanced to after the record.
extern Status ReadRecordFromWriteBatch(Slice* input, char* tag,
uint32_t* column_family, Slice* key,
Slice* value, Slice* blob, Slice* xid);
// When user call DeleteRange() to delete a range of keys,
// we will store a serialized RangeTombstone in MemTable and SST.
// the struct here is a easy-understood form
// start/end_key_ is the start/end user key of the range to be deleted
struct RangeTombstone {
Slice start_key_;
Slice end_key_;
SequenceNumber seq_;
RangeTombstone() = default;
RangeTombstone(Slice sk, Slice ek, SequenceNumber sn)
: start_key_(sk), end_key_(ek), seq_(sn) {}
RangeTombstone(ParsedInternalKey parsed_key, Slice value) {
start_key_ = parsed_key.user_key;
seq_ = parsed_key.sequence;
end_key_ = value;
}
// be careful to use Serialize(), allocates new memory
std::pair<InternalKey, Slice> Serialize() const {
auto key = InternalKey(start_key_, seq_, kTypeRangeDeletion);
Slice value = end_key_;
return std::make_pair(std::move(key), std::move(value));
}
// be careful to use SerializeKey(), allocates new memory
InternalKey SerializeKey() const {
return InternalKey(start_key_, seq_, kTypeRangeDeletion);
}
// be careful to use SerializeEndKey(), allocates new memory
InternalKey SerializeEndKey() const {
return InternalKey(end_key_, seq_, kTypeRangeDeletion);
}
};
inline
int InternalKeyComparator::Compare(const Slice& akey, const Slice& bkey) const {
// Order by:
// increasing user key (according to user-supplied comparator)
// decreasing sequence number
// decreasing type (though sequence# should be enough to disambiguate)
int r = user_comparator_->Compare(ExtractUserKey(akey), ExtractUserKey(bkey));
PERF_COUNTER_ADD(user_key_comparison_count, 1);
if (r == 0) {
const uint64_t anum = DecodeFixed64(akey.data() + akey.size() - 8);
const uint64_t bnum = DecodeFixed64(bkey.data() + bkey.size() - 8);
if (anum > bnum) {
r = -1;
} else if (anum < bnum) {
r = +1;
}
}
return r;
}
inline
int InternalKeyComparator::CompareKeySeq(const Slice& akey,
const Slice& bkey) const {
// Order by:
// increasing user key (according to user-supplied comparator)
// decreasing sequence number
int r = user_comparator_->Compare(ExtractUserKey(akey), ExtractUserKey(bkey));
PERF_COUNTER_ADD(user_key_comparison_count, 1);
if (r == 0) {
// Shift the number to exclude the last byte which contains the value type
const uint64_t anum = DecodeFixed64(akey.data() + akey.size() - 8) >> 8;
const uint64_t bnum = DecodeFixed64(bkey.data() + bkey.size() - 8) >> 8;
if (anum > bnum) {
r = -1;
} else if (anum < bnum) {
r = +1;
}
}
return r;
}
} // namespace rocksdb