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74781a0c49
Summary: This patch adds three new MemTableRep's: UnsortedRep, PrefixHashRep, and VectorRep. UnsortedRep stores keys in an std::unordered_map of std::sets. When an iterator is requested, it dumps the keys into an std::set and iterates over that. VectorRep stores keys in an std::vector. When an iterator is requested, it creates a copy of the vector and sorts it using std::sort. The iterator accesses that new vector. PrefixHashRep stores keys in an unordered_map mapping prefixes to ordered sets. I also added one API change. I added a function MemTableRep::MarkImmutable. This function is called when the rep is added to the immutable list. It doesn't do anything yet, but it seems like that could be useful. In particular, for the vectorrep, it means we could elide the extra copy and just sort in place. The only reason I haven't done that yet is because the use of the ArenaAllocator complicates things (I can elaborate on this if needed). Test Plan: make -j32 check ./db_stress --memtablerep=vector ./db_stress --memtablerep=unsorted ./db_stress --memtablerep=prefixhash --prefix_size=10 Reviewers: dhruba, haobo, emayanke Reviewed By: dhruba CC: leveldb Differential Revision: https://reviews.facebook.net/D12117
123 lines
3.4 KiB
C++
123 lines
3.4 KiB
C++
// 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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//
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// Slice is a simple structure containing a pointer into some external
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// storage and a size. The user of a Slice must ensure that the slice
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// is not used after the corresponding external storage has been
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// deallocated.
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//
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// Multiple threads can invoke const methods on a Slice without
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// external synchronization, but if any of the threads may call a
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// non-const method, all threads accessing the same Slice must use
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// external synchronization.
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#ifndef STORAGE_LEVELDB_INCLUDE_SLICE_H_
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#define STORAGE_LEVELDB_INCLUDE_SLICE_H_
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#include <assert.h>
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#include <stddef.h>
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#include <string.h>
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#include <string>
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namespace leveldb {
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class Slice {
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public:
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// Create an empty slice.
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Slice() : data_(""), size_(0) { }
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// Create a slice that refers to d[0,n-1].
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Slice(const char* d, size_t n) : data_(d), size_(n) { }
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// Create a slice that refers to the contents of "s"
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/* implicit */
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Slice(const std::string& s) : data_(s.data()), size_(s.size()) { }
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// Create a slice that refers to s[0,strlen(s)-1]
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/* implicit */
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Slice(const char* s) : data_(s), size_(strlen(s)) { }
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// Return a pointer to the beginning of the referenced data
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const char* data() const { return data_; }
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// Return the length (in bytes) of the referenced data
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size_t size() const { return size_; }
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// Return true iff the length of the referenced data is zero
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bool empty() const { return size_ == 0; }
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// Return the ith byte in the referenced data.
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// REQUIRES: n < size()
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char operator[](size_t n) const {
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assert(n < size());
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return data_[n];
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}
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// Change this slice to refer to an empty array
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void clear() { data_ = ""; size_ = 0; }
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// Drop the first "n" bytes from this slice.
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void remove_prefix(size_t n) {
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assert(n <= size());
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data_ += n;
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size_ -= n;
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}
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// Return a string that contains the copy of the referenced data.
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std::string ToString(bool hex = false) const {
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if (hex) {
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std::string result;
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char buf[10];
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for (size_t i = 0; i < size_; i++) {
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snprintf(buf, 10, "%02X", (unsigned char)data_[i]);
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result += buf;
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}
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return result;
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} else {
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return std::string(data_, size_);
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}
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}
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// Three-way comparison. Returns value:
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// < 0 iff "*this" < "b",
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// == 0 iff "*this" == "b",
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// > 0 iff "*this" > "b"
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int compare(const Slice& b) const;
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// Return true iff "x" is a prefix of "*this"
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bool starts_with(const Slice& x) const {
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return ((size_ >= x.size_) &&
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(memcmp(data_, x.data_, x.size_) == 0));
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}
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// private: make these public for leveldbjni access
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const char* data_;
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size_t size_;
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// Intentionally copyable
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};
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inline bool operator==(const Slice& x, const Slice& y) {
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return ((x.size() == y.size()) &&
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(memcmp(x.data(), y.data(), x.size()) == 0));
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}
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inline bool operator!=(const Slice& x, const Slice& y) {
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return !(x == y);
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}
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inline int Slice::compare(const Slice& b) const {
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const int min_len = (size_ < b.size_) ? size_ : b.size_;
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int r = memcmp(data_, b.data_, min_len);
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if (r == 0) {
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if (size_ < b.size_) r = -1;
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else if (size_ > b.size_) r = +1;
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}
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return r;
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}
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_INCLUDE_SLICE_H_
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