mirror of
https://github.com/facebook/rocksdb.git
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da9274574f
Summary: Modify a functioin TrimAppend in dbformat.h: IterKey. Write a test for it in dbformat_test Use IterKey in block::Iter to replace std::string to reduce malloc. Evaluate it using perf record. malloc: 4.26% -> 2.91% free: 3.61% -> 3.08% Test Plan: make all check ./valgrind db_test dbformat_test Reviewers: ljin, haobo, yhchiang, dhruba, igor, sdong Reviewed By: sdong Differential Revision: https://reviews.facebook.net/D20433
405 lines
13 KiB
C++
405 lines
13 KiB
C++
// Copyright (c) 2013, 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 <stdio.h>
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#include <string>
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#include "rocksdb/comparator.h"
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#include "rocksdb/db.h"
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#include "rocksdb/filter_policy.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/slice_transform.h"
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#include "rocksdb/table.h"
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#include "rocksdb/types.h"
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#include "util/coding.h"
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#include "util/logging.h"
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namespace rocksdb {
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class InternalKey;
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// Value types encoded as the last component of internal keys.
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// DO NOT CHANGE THESE ENUM VALUES: they are embedded in the on-disk
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// data structures.
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// The highest bit of the value type needs to be reserved to SST tables
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// for them to do more flexible encoding.
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enum ValueType : unsigned char {
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kTypeDeletion = 0x0,
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kTypeValue = 0x1,
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kTypeMerge = 0x2,
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// Following types are used only in write ahead logs. They are not used in
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// memtables or sst files:
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kTypeLogData = 0x3,
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kTypeColumnFamilyDeletion = 0x4,
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kTypeColumnFamilyValue = 0x5,
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kTypeColumnFamilyMerge = 0x6,
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kMaxValue = 0x7F
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};
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// kValueTypeForSeek defines the ValueType that should be passed when
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// constructing a ParsedInternalKey object for seeking to a particular
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// sequence number (since we sort sequence numbers in decreasing order
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// and the value type is embedded as the low 8 bits in the sequence
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// number in internal keys, we need to use the highest-numbered
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// ValueType, not the lowest).
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static const ValueType kValueTypeForSeek = kTypeMerge;
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// We leave eight bits empty at the bottom so a type and sequence#
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// can be packed together into 64-bits.
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static const SequenceNumber kMaxSequenceNumber =
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((0x1ull << 56) - 1);
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struct ParsedInternalKey {
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Slice user_key;
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SequenceNumber sequence;
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ValueType type;
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ParsedInternalKey() { } // Intentionally left uninitialized (for speed)
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ParsedInternalKey(const Slice& u, const SequenceNumber& seq, ValueType t)
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: user_key(u), sequence(seq), type(t) { }
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std::string DebugString(bool hex = false) const;
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};
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// Return the length of the encoding of "key".
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inline size_t InternalKeyEncodingLength(const ParsedInternalKey& key) {
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return key.user_key.size() + 8;
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}
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extern uint64_t PackSequenceAndType(uint64_t seq, ValueType t);
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// Append the serialization of "key" to *result.
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extern void AppendInternalKey(std::string* result,
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const ParsedInternalKey& key);
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// Attempt to parse an internal key from "internal_key". On success,
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// stores the parsed data in "*result", and returns true.
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//
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// On error, returns false, leaves "*result" in an undefined state.
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extern bool ParseInternalKey(const Slice& internal_key,
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ParsedInternalKey* result);
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// Returns the user key portion of an internal key.
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inline Slice ExtractUserKey(const Slice& internal_key) {
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assert(internal_key.size() >= 8);
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return Slice(internal_key.data(), internal_key.size() - 8);
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}
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inline ValueType ExtractValueType(const Slice& internal_key) {
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assert(internal_key.size() >= 8);
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const size_t n = internal_key.size();
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uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
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unsigned char c = num & 0xff;
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return static_cast<ValueType>(c);
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}
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// A comparator for internal keys that uses a specified comparator for
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// the user key portion and breaks ties by decreasing sequence number.
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class InternalKeyComparator : public Comparator {
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private:
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const Comparator* user_comparator_;
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std::string name_;
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public:
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explicit InternalKeyComparator(const Comparator* c) : user_comparator_(c),
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name_("rocksdb.InternalKeyComparator:" +
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std::string(user_comparator_->Name())) {
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}
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virtual ~InternalKeyComparator() {}
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virtual const char* Name() const;
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virtual int Compare(const Slice& a, const Slice& b) const;
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virtual void FindShortestSeparator(
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std::string* start,
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const Slice& limit) const;
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virtual void FindShortSuccessor(std::string* key) const;
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const Comparator* user_comparator() const { return user_comparator_; }
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int Compare(const InternalKey& a, const InternalKey& b) const;
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int Compare(const ParsedInternalKey& a, const ParsedInternalKey& b) const;
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};
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// Filter policy wrapper that converts from internal keys to user keys
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class InternalFilterPolicy : public FilterPolicy {
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private:
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const FilterPolicy* const user_policy_;
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public:
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explicit InternalFilterPolicy(const FilterPolicy* p) : user_policy_(p) { }
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virtual const char* Name() const;
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virtual void CreateFilter(const Slice* keys, int n, std::string* dst) const;
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virtual bool KeyMayMatch(const Slice& key, const Slice& filter) const;
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};
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// Modules in this directory should keep internal keys wrapped inside
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// the following class instead of plain strings so that we do not
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// incorrectly use string comparisons instead of an InternalKeyComparator.
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class InternalKey {
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private:
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std::string rep_;
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public:
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InternalKey() { } // Leave rep_ as empty to indicate it is invalid
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InternalKey(const Slice& user_key, SequenceNumber s, ValueType t) {
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AppendInternalKey(&rep_, ParsedInternalKey(user_key, s, t));
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}
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bool Valid() const {
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ParsedInternalKey parsed;
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return ParseInternalKey(Slice(rep_), &parsed);
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}
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void DecodeFrom(const Slice& s) { rep_.assign(s.data(), s.size()); }
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Slice Encode() const {
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assert(!rep_.empty());
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return rep_;
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}
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Slice user_key() const { return ExtractUserKey(rep_); }
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void SetFrom(const ParsedInternalKey& p) {
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rep_.clear();
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AppendInternalKey(&rep_, p);
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}
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void Clear() { rep_.clear(); }
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std::string DebugString(bool hex = false) const;
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};
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inline int InternalKeyComparator::Compare(
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const InternalKey& a, const InternalKey& b) const {
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return Compare(a.Encode(), b.Encode());
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}
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inline bool ParseInternalKey(const Slice& internal_key,
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ParsedInternalKey* result) {
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const size_t n = internal_key.size();
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if (n < 8) return false;
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uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
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unsigned char c = num & 0xff;
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result->sequence = num >> 8;
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result->type = static_cast<ValueType>(c);
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assert(result->type <= ValueType::kMaxValue);
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result->user_key = Slice(internal_key.data(), n - 8);
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return (c <= static_cast<unsigned char>(kValueTypeForSeek));
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}
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// Update the sequence number in the internal key
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inline void UpdateInternalKey(char* internal_key,
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const size_t internal_key_size,
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uint64_t seq, ValueType t) {
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assert(internal_key_size >= 8);
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char* seqtype = internal_key + internal_key_size - 8;
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uint64_t newval = (seq << 8) | t;
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EncodeFixed64(seqtype, newval);
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}
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// Get the sequence number from the internal key
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inline uint64_t GetInternalKeySeqno(const Slice& internal_key) {
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const size_t n = internal_key.size();
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assert(n >= 8);
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uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
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return num >> 8;
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}
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// A helper class useful for DBImpl::Get()
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class LookupKey {
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public:
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// Initialize *this for looking up user_key at a snapshot with
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// the specified sequence number.
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LookupKey(const Slice& user_key, SequenceNumber sequence);
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~LookupKey();
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// Return a key suitable for lookup in a MemTable.
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Slice memtable_key() const { return Slice(start_, end_ - start_); }
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// Return an internal key (suitable for passing to an internal iterator)
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Slice internal_key() const { return Slice(kstart_, end_ - kstart_); }
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// Return the user key
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Slice user_key() const { return Slice(kstart_, end_ - kstart_ - 8); }
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private:
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// We construct a char array of the form:
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// klength varint32 <-- start_
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// userkey char[klength] <-- kstart_
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// tag uint64
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// <-- end_
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// The array is a suitable MemTable key.
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// The suffix starting with "userkey" can be used as an InternalKey.
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const char* start_;
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const char* kstart_;
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const char* end_;
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char space_[200]; // Avoid allocation for short keys
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// No copying allowed
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LookupKey(const LookupKey&);
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void operator=(const LookupKey&);
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};
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inline LookupKey::~LookupKey() {
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if (start_ != space_) delete[] start_;
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}
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class IterKey {
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public:
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IterKey() : key_(space_), buf_size_(sizeof(space_)), key_size_(0) {}
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~IterKey() { ResetBuffer(); }
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Slice GetKey() const { return Slice(key_, key_size_); }
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const size_t Size() { return key_size_; }
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void Clear() { key_size_ = 0; }
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// Append "non_shared_data" to its back, from "shared_len"
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// This function is used in Block::Iter::ParseNextKey
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// shared_len: bytes in [0, shard_len-1] would be remained
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// non_shared_data: data to be append, its length must be >= non_shared_len
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void TrimAppend(const size_t shared_len, const char* non_shared_data,
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const size_t non_shared_len) {
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assert(shared_len <= key_size_);
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size_t total_size = shared_len + non_shared_len;
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if (total_size <= buf_size_) {
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key_size_ = total_size;
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} else {
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// Need to allocate space, delete previous space
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char* p = new char[total_size];
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memcpy(p, key_, shared_len);
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if (key_ != nullptr && key_ != space_) {
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delete[] key_;
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}
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key_ = p;
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key_size_ = total_size;
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buf_size_ = total_size;
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}
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memcpy(key_ + shared_len, non_shared_data, non_shared_len);
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}
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void SetKey(const Slice& key) {
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size_t size = key.size();
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EnlargeBufferIfNeeded(size);
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memcpy(key_, key.data(), size);
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key_size_ = size;
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}
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void SetInternalKey(const Slice& key_prefix, const Slice& user_key,
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SequenceNumber s,
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ValueType value_type = kValueTypeForSeek) {
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size_t psize = key_prefix.size();
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size_t usize = user_key.size();
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EnlargeBufferIfNeeded(psize + usize + sizeof(uint64_t));
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if (psize > 0) {
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memcpy(key_, key_prefix.data(), psize);
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}
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memcpy(key_ + psize, user_key.data(), usize);
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EncodeFixed64(key_ + usize + psize, PackSequenceAndType(s, value_type));
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key_size_ = psize + usize + sizeof(uint64_t);
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}
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void SetInternalKey(const Slice& user_key, SequenceNumber s,
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ValueType value_type = kValueTypeForSeek) {
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SetInternalKey(Slice(), user_key, s, value_type);
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}
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void Reserve(size_t size) {
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EnlargeBufferIfNeeded(size);
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key_size_ = size;
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}
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void SetInternalKey(const ParsedInternalKey& parsed_key) {
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SetInternalKey(Slice(), parsed_key);
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}
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void SetInternalKey(const Slice& key_prefix,
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const ParsedInternalKey& parsed_key_suffix) {
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SetInternalKey(key_prefix, parsed_key_suffix.user_key,
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parsed_key_suffix.sequence, parsed_key_suffix.type);
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}
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void EncodeLengthPrefixedKey(const Slice& key) {
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auto size = key.size();
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EnlargeBufferIfNeeded(size + VarintLength(size));
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char* ptr = EncodeVarint32(key_, size);
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memcpy(ptr, key.data(), size);
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}
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private:
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char* key_;
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size_t buf_size_;
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size_t key_size_;
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char space_[32]; // Avoid allocation for short keys
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void ResetBuffer() {
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if (key_ != nullptr && key_ != space_) {
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delete[] key_;
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}
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key_ = space_;
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buf_size_ = sizeof(space_);
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key_size_ = 0;
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}
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// Enlarge the buffer size if needed based on key_size.
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// By default, static allocated buffer is used. Once there is a key
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// larger than the static allocated buffer, another buffer is dynamically
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// allocated, until a larger key buffer is requested. In that case, we
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// reallocate buffer and delete the old one.
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void EnlargeBufferIfNeeded(size_t key_size) {
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// If size is smaller than buffer size, continue using current buffer,
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// or the static allocated one, as default
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if (key_size > buf_size_) {
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// Need to enlarge the buffer.
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ResetBuffer();
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key_ = new char[key_size];
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buf_size_ = key_size;
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}
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}
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// No copying allowed
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IterKey(const IterKey&) = delete;
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void operator=(const IterKey&) = delete;
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};
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class InternalKeySliceTransform : public SliceTransform {
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public:
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explicit InternalKeySliceTransform(const SliceTransform* transform)
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: transform_(transform) {}
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virtual const char* Name() const { return transform_->Name(); }
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virtual Slice Transform(const Slice& src) const {
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auto user_key = ExtractUserKey(src);
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return transform_->Transform(user_key);
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}
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virtual bool InDomain(const Slice& src) const {
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auto user_key = ExtractUserKey(src);
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return transform_->InDomain(user_key);
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}
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virtual bool InRange(const Slice& dst) const {
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auto user_key = ExtractUserKey(dst);
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return transform_->InRange(user_key);
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}
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const SliceTransform* user_prefix_extractor() const { return transform_; }
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private:
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// Like comparator, InternalKeySliceTransform will not take care of the
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// deletion of transform_
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const SliceTransform* const transform_;
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};
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} // namespace rocksdb
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