rocksdb/db/dbformat.h
Andrew Kryczka 50e305de98 Collapse range deletions
Summary:
Added a tombstone-collapsing mode to RangeDelAggregator, which eliminates overlap in the TombstoneMap. In this mode, we can check whether a tombstone covers a user key using upper_bound() (i.e., binary search). However, the tradeoff is the overhead to add tombstones is now higher, so at first I've only enabled it for range scans (compaction/flush/user iterators), where we expect a high number of calls to ShouldDelete() for the same tombstones. Point queries like Get() will still use the linear scan approach.

Also in this diff I changed RangeDelAggregator's TombstoneMap to use multimap with user keys instead of map with internal keys. Callers sometimes provided ParsedInternalKey directly, from which it would've required string copying to derive an internal key Slice with which we could search the map.
Closes https://github.com/facebook/rocksdb/pull/1614

Differential Revision: D4270397

Pulled By: ajkr

fbshipit-source-id: 93092c7
2016-12-19 16:54:12 -08:00

560 lines
18 KiB
C++

// 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.
//
// 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 "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
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;
}
// 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() { } // 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;
};
// 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);
// 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 : 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;
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;
};
// 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, kMaxSequenceNumber,
kValueTypeForSeek));
}
// 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, 0, static_cast<ValueType>(0)));
}
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) {}
~IterKey() { ResetBuffer(); }
Slice GetKey() const { return Slice(key_, key_size_); }
Slice GetUserKey() const {
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 SetKey(const Slice& key, bool copy = true) {
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_);
}
// Copies the content of key, updates the reference to the user key in ikey
// and returns a Slice referencing the new copy.
Slice SetKey(const Slice& key, ParsedInternalKey* ikey) {
size_t key_n = key.size();
assert(key_n >= 8);
SetKey(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);
}
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_;
}
private:
char* buf_;
size_t buf_size_;
const char* key_;
size_t key_size_;
char space_[32]; // Avoid allocation for short keys
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_) {
// Need to enlarge the buffer.
ResetBuffer();
buf_ = new char[key_size];
buf_size_ = 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);
}
};
} // namespace rocksdb