a143ef9b38
Summary: Change namespace from leveldb to rocksdb. This allows a single application to link in open-source leveldb code as well as rocksdb code into the same process. Test Plan: compile rocksdb Reviewers: emayanke Reviewed By: emayanke CC: leveldb Differential Revision: https://reviews.facebook.net/D13287
499 lines
17 KiB
C++
499 lines
17 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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#include "table/table.h"
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#include "db/dbformat.h"
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#include "rocksdb/cache.h"
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#include "rocksdb/comparator.h"
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#include "rocksdb/env.h"
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#include "rocksdb/filter_policy.h"
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#include "rocksdb/options.h"
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#include "rocksdb/statistics.h"
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#include "table/block.h"
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#include "table/filter_block.h"
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#include "table/format.h"
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#include "table/two_level_iterator.h"
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#include "util/coding.h"
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#include "util/perf_context_imp.h"
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#include "util/stop_watch.h"
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namespace rocksdb {
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// The longest the prefix of the cache key used to identify blocks can be.
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// We are using the fact that we know for Posix files the unique ID is three
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// varints.
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const size_t kMaxCacheKeyPrefixSize = kMaxVarint64Length*3+1;
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struct Table::Rep {
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~Rep() {
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delete filter;
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delete [] filter_data;
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delete index_block;
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}
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Rep(const EnvOptions& storage_options) :
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soptions(storage_options) {
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}
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Options options;
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const EnvOptions& soptions;
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Status status;
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unique_ptr<RandomAccessFile> file;
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char cache_key_prefix[kMaxCacheKeyPrefixSize];
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size_t cache_key_prefix_size;
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FilterBlockReader* filter;
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const char* filter_data;
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BlockHandle metaindex_handle; // Handle to metaindex_block: saved from footer
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Block* index_block;
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};
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// Helper function to setup the cache key's prefix for the Table.
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void Table::SetupCacheKeyPrefix(Rep* rep) {
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assert(kMaxCacheKeyPrefixSize >= 10);
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rep->cache_key_prefix_size = 0;
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if (rep->options.block_cache) {
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rep->cache_key_prefix_size = rep->file->GetUniqueId(rep->cache_key_prefix,
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kMaxCacheKeyPrefixSize);
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if (rep->cache_key_prefix_size == 0) {
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// If the prefix wasn't generated or was too long, we create one from the
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// cache.
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char* end = EncodeVarint64(rep->cache_key_prefix,
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rep->options.block_cache->NewId());
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rep->cache_key_prefix_size =
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static_cast<size_t>(end - rep->cache_key_prefix);
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}
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}
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}
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namespace { // anonymous namespace, not visible externally
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// Read the block identified by "handle" from "file".
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// The only relevant option is options.verify_checksums for now.
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// Set *didIO to true if didIO is not null.
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// On failure return non-OK.
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// On success fill *result and return OK - caller owns *result
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Status ReadBlock(RandomAccessFile* file,
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const ReadOptions& options,
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const BlockHandle& handle,
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Block** result,
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Env* env,
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bool* didIO = nullptr) {
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BlockContents contents;
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Status s = ReadBlockContents(file, options, handle, &contents, env);
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if (s.ok()) {
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*result = new Block(contents);
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}
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if (didIO) {
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*didIO = true;
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}
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return s;
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}
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} // end of anonymous namespace
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Status Table::Open(const Options& options,
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const EnvOptions& soptions,
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unique_ptr<RandomAccessFile>&& file,
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uint64_t size,
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unique_ptr<Table>* table) {
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table->reset();
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if (size < Footer::kEncodedLength) {
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return Status::InvalidArgument("file is too short to be an sstable");
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}
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char footer_space[Footer::kEncodedLength];
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Slice footer_input;
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Status s = file->Read(size - Footer::kEncodedLength, Footer::kEncodedLength,
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&footer_input, footer_space);
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if (!s.ok()) return s;
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// Check that we actually read the whole footer from the file. It may be
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// that size isn't correct.
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if (footer_input.size() != Footer::kEncodedLength) {
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return Status::InvalidArgument("file is too short to be an sstable");
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}
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Footer footer;
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s = footer.DecodeFrom(&footer_input);
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if (!s.ok()) return s;
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Block* index_block = nullptr;
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// TODO: we never really verify check sum for index block
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s = ReadBlock(file.get(), ReadOptions(), footer.index_handle(), &index_block,
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options.env);
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if (s.ok()) {
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// We've successfully read the footer and the index block: we're
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// ready to serve requests.
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Rep* rep = new Table::Rep(soptions);
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rep->options = options;
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rep->file = std::move(file);
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rep->metaindex_handle = footer.metaindex_handle();
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rep->index_block = index_block;
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SetupCacheKeyPrefix(rep);
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rep->filter_data = nullptr;
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rep->filter = nullptr;
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table->reset(new Table(rep));
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(*table)->ReadMeta(footer);
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} else {
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if (index_block) delete index_block;
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}
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return s;
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}
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void Table::SetupForCompaction() {
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switch (rep_->options.access_hint_on_compaction_start) {
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case Options::NONE:
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break;
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case Options::NORMAL:
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rep_->file->Hint(RandomAccessFile::NORMAL);
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break;
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case Options::SEQUENTIAL:
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rep_->file->Hint(RandomAccessFile::SEQUENTIAL);
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break;
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case Options::WILLNEED:
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rep_->file->Hint(RandomAccessFile::WILLNEED);
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break;
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default:
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assert(false);
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}
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compaction_optimized_ = true;
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}
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void Table::ReadMeta(const Footer& footer) {
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if (rep_->options.filter_policy == nullptr) {
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return; // Do not need any metadata
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}
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// TODO(sanjay): Skip this if footer.metaindex_handle() size indicates
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// it is an empty block.
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// TODO: we never really verify check sum for meta index block
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Block* meta = nullptr;
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if (!ReadBlock(rep_->file.get(), ReadOptions(), footer.metaindex_handle(),
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&meta, rep_->options.env).ok()) {
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// Do not propagate errors since meta info is not needed for operation
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return;
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}
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Iterator* iter = meta->NewIterator(BytewiseComparator());
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std::string key = "filter.";
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key.append(rep_->options.filter_policy->Name());
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iter->Seek(key);
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if (iter->Valid() && iter->key() == Slice(key)) {
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ReadFilter(iter->value());
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}
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delete iter;
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delete meta;
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}
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void Table::ReadFilter(const Slice& filter_handle_value) {
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Slice v = filter_handle_value;
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BlockHandle filter_handle;
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if (!filter_handle.DecodeFrom(&v).ok()) {
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return;
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}
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// TODO: We might want to unify with ReadBlock() if we start
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// requiring checksum verification in Table::Open.
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ReadOptions opt;
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BlockContents block;
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if (!ReadBlockContents(rep_->file.get(), opt, filter_handle, &block,
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rep_->options.env).ok()) {
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return;
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}
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if (block.heap_allocated) {
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rep_->filter_data = block.data.data(); // Will need to delete later
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}
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rep_->filter = new FilterBlockReader(rep_->options, block.data);
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}
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Table::~Table() {
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delete rep_;
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}
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static void DeleteBlock(void* arg, void* ignored) {
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delete reinterpret_cast<Block*>(arg);
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}
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static void DeleteCachedBlock(const Slice& key, void* value) {
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Block* block = reinterpret_cast<Block*>(value);
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delete block;
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}
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static void ReleaseBlock(void* arg, void* h) {
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Cache* cache = reinterpret_cast<Cache*>(arg);
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Cache::Handle* handle = reinterpret_cast<Cache::Handle*>(h);
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cache->Release(handle);
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}
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// Convert an index iterator value (i.e., an encoded BlockHandle)
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// into an iterator over the contents of the corresponding block.
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Iterator* Table::BlockReader(void* arg,
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const ReadOptions& options,
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const Slice& index_value,
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bool* didIO,
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bool for_compaction) {
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const bool no_io = (options.read_tier == kBlockCacheTier);
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Table* table = reinterpret_cast<Table*>(arg);
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Cache* block_cache = table->rep_->options.block_cache.get();
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std::shared_ptr<Statistics> statistics = table->rep_->options.statistics;
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Block* block = nullptr;
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Cache::Handle* cache_handle = nullptr;
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BlockHandle handle;
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Slice input = index_value;
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Status s = handle.DecodeFrom(&input);
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// We intentionally allow extra stuff in index_value so that we
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// can add more features in the future.
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if (s.ok()) {
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if (block_cache != nullptr) {
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char cache_key[kMaxCacheKeyPrefixSize + kMaxVarint64Length];
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const size_t cache_key_prefix_size = table->rep_->cache_key_prefix_size;
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assert(cache_key_prefix_size != 0);
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assert(cache_key_prefix_size <= kMaxCacheKeyPrefixSize);
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memcpy(cache_key, table->rep_->cache_key_prefix,
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cache_key_prefix_size);
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char* end = EncodeVarint64(cache_key + cache_key_prefix_size,
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handle.offset());
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Slice key(cache_key, static_cast<size_t>(end-cache_key));
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cache_handle = block_cache->Lookup(key);
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if (cache_handle != nullptr) {
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block = reinterpret_cast<Block*>(block_cache->Value(cache_handle));
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BumpPerfCount(&perf_context.block_cache_hit_count);
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RecordTick(statistics, BLOCK_CACHE_HIT);
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} else if (no_io) {
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// Did not find in block_cache and can't do IO
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return NewErrorIterator(Status::Incomplete("no blocking io"));
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} else {
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Histograms histogram = for_compaction ?
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READ_BLOCK_COMPACTION_MICROS : READ_BLOCK_GET_MICROS;
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{ // block for stop watch
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StopWatch sw(table->rep_->options.env, statistics, histogram);
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s = ReadBlock(
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table->rep_->file.get(),
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options,
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handle,
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&block,
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table->rep_->options.env,
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didIO
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);
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}
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if (s.ok()) {
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if (block->isCachable() && options.fill_cache) {
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cache_handle = block_cache->Insert(
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key, block, block->size(), &DeleteCachedBlock);
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}
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}
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RecordTick(statistics, BLOCK_CACHE_MISS);
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}
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} else if (no_io) {
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// Could not read from block_cache and can't do IO
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return NewErrorIterator(Status::Incomplete("no blocking io"));
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} else {
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s = ReadBlock(table->rep_->file.get(), options, handle, &block,
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table->rep_->options.env, didIO);
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}
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}
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Iterator* iter;
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if (block != nullptr) {
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iter = block->NewIterator(table->rep_->options.comparator);
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if (cache_handle == nullptr) {
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iter->RegisterCleanup(&DeleteBlock, block, nullptr);
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} else {
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iter->RegisterCleanup(&ReleaseBlock, block_cache, cache_handle);
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}
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} else {
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iter = NewErrorIterator(s);
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}
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return iter;
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}
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Iterator* Table::BlockReader(void* arg,
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const ReadOptions& options,
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const EnvOptions& soptions,
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const Slice& index_value,
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bool for_compaction) {
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return BlockReader(arg, options, index_value, nullptr, for_compaction);
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}
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// This will be broken if the user specifies an unusual implementation
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// of Options.comparator, or if the user specifies an unusual
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// definition of prefixes in Options.filter_policy. In particular, we
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// require the following three properties:
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//
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// 1) key.starts_with(prefix(key))
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// 2) Compare(prefix(key), key) <= 0.
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// 3) If Compare(key1, key2) <= 0, then Compare(prefix(key1), prefix(key2)) <= 0
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//
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// TODO(tylerharter): right now, this won't cause I/O since blooms are
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// in memory. When blooms may need to be paged in, we should refactor so that
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// this is only ever called lazily. In particular, this shouldn't be called
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// while the DB lock is held like it is now.
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bool Table::PrefixMayMatch(const Slice& internal_prefix) const {
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FilterBlockReader* filter = rep_->filter;
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bool may_match = true;
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Status s;
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if (filter == nullptr) {
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return true;
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}
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std::unique_ptr<Iterator> iiter(rep_->index_block->NewIterator(
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rep_->options.comparator));
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iiter->Seek(internal_prefix);
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if (!iiter->Valid()) {
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// we're past end of file
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may_match = false;
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} else if (ExtractUserKey(iiter->key()).starts_with(
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ExtractUserKey(internal_prefix))) {
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// we need to check for this subtle case because our only
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// guarantee is that "the key is a string >= last key in that data
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// block" according to the doc/table_format.txt spec.
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//
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// Suppose iiter->key() starts with the desired prefix; it is not
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// necessarily the case that the corresponding data block will
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// contain the prefix, since iiter->key() need not be in the
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// block. However, the next data block may contain the prefix, so
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// we return true to play it safe.
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may_match = true;
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} else {
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// iiter->key() does NOT start with the desired prefix. Because
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// Seek() finds the first key that is >= the seek target, this
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// means that iiter->key() > prefix. Thus, any data blocks coming
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// after the data block corresponding to iiter->key() cannot
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// possibly contain the key. Thus, the corresponding data block
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// is the only one which could potentially contain the prefix.
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Slice handle_value = iiter->value();
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BlockHandle handle;
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s = handle.DecodeFrom(&handle_value);
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assert(s.ok());
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may_match = filter->PrefixMayMatch(handle.offset(), internal_prefix);
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}
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RecordTick(rep_->options.statistics, BLOOM_FILTER_PREFIX_CHECKED);
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if (!may_match) {
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RecordTick(rep_->options.statistics, BLOOM_FILTER_PREFIX_USEFUL);
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}
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return may_match;
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}
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Iterator* Table::NewIterator(const ReadOptions& options) const {
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if (options.prefix) {
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InternalKey internal_prefix(*options.prefix, 0, kTypeValue);
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if (!PrefixMayMatch(internal_prefix.Encode())) {
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// nothing in this file can match the prefix, so we should not
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// bother doing I/O to this file when iterating.
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return NewEmptyIterator();
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}
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}
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return NewTwoLevelIterator(
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rep_->index_block->NewIterator(rep_->options.comparator),
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&Table::BlockReader, const_cast<Table*>(this), options, rep_->soptions);
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}
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Status Table::InternalGet(const ReadOptions& options, const Slice& k,
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void* arg,
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bool (*saver)(void*, const Slice&, const Slice&,
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bool),
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void (*mark_key_may_exist)(void*)) {
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Status s;
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Iterator* iiter = rep_->index_block->NewIterator(rep_->options.comparator);
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bool done = false;
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for (iiter->Seek(k); iiter->Valid() && !done; iiter->Next()) {
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Slice handle_value = iiter->value();
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FilterBlockReader* filter = rep_->filter;
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BlockHandle handle;
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if (filter != nullptr &&
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handle.DecodeFrom(&handle_value).ok() &&
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!filter->KeyMayMatch(handle.offset(), k)) {
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// Not found
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// TODO: think about interaction with Merge. If a user key cannot
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// cross one data block, we should be fine.
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RecordTick(rep_->options.statistics, BLOOM_FILTER_USEFUL);
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break;
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} else {
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bool didIO = false;
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std::unique_ptr<Iterator> block_iter(
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BlockReader(this, options, iiter->value(), &didIO));
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if (options.read_tier && block_iter->status().IsIncomplete()) {
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// couldn't get block from block_cache
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// Update Saver.state to Found because we are only looking for whether
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// we can guarantee the key is not there when "no_io" is set
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(*mark_key_may_exist)(arg);
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break;
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}
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// Call the *saver function on each entry/block until it returns false
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for (block_iter->Seek(k); block_iter->Valid(); block_iter->Next()) {
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if (!(*saver)(arg, block_iter->key(), block_iter->value(), didIO)) {
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done = true;
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break;
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}
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}
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s = block_iter->status();
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}
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}
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if (s.ok()) {
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s = iiter->status();
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}
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delete iiter;
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return s;
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}
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bool SaveDidIO(void* arg, const Slice& key, const Slice& value, bool didIO) {
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*reinterpret_cast<bool*>(arg) = didIO;
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return false;
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}
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bool Table::TEST_KeyInCache(const ReadOptions& options, const Slice& key) {
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// We use InternalGet() as it has logic that checks whether we read the
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// block from the disk or not.
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bool didIO = false;
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Status s = InternalGet(options, key, &didIO, SaveDidIO);
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assert(s.ok());
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return !didIO;
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}
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uint64_t Table::ApproximateOffsetOf(const Slice& key) const {
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Iterator* index_iter =
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rep_->index_block->NewIterator(rep_->options.comparator);
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index_iter->Seek(key);
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uint64_t result;
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if (index_iter->Valid()) {
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BlockHandle handle;
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Slice input = index_iter->value();
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Status s = handle.DecodeFrom(&input);
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if (s.ok()) {
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result = handle.offset();
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} else {
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// Strange: we can't decode the block handle in the index block.
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// We'll just return the offset of the metaindex block, which is
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// close to the whole file size for this case.
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result = rep_->metaindex_handle.offset();
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}
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} else {
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// key is past the last key in the file. Approximate the offset
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// by returning the offset of the metaindex block (which is
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// right near the end of the file).
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result = rep_->metaindex_handle.offset();
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}
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delete index_iter;
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return result;
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}
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} // namespace rocksdb
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