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175 行
5.2 KiB
175 行
5.2 KiB
// 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 "leveldb/table.h"
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#include "leveldb/cache.h"
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#include "leveldb/env.h"
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#include "table/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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namespace leveldb {
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struct Table::Rep {
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~Rep() {
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delete index_block;
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}
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Options options;
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Status status;
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RandomAccessFile* file;
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uint64_t cache_id;
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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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Status Table::Open(const Options& options,
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RandomAccessFile* file,
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uint64_t size,
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Table** table) {
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*table = NULL;
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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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Footer footer;
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s = footer.DecodeFrom(&footer_input);
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if (!s.ok()) return s;
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// Read the index block
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Block* index_block = NULL;
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if (s.ok()) {
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s = ReadBlock(file, ReadOptions(), footer.index_handle(), &index_block);
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}
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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;
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rep->options = options;
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rep->file = file;
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rep->metaindex_handle = footer.metaindex_handle();
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rep->index_block = index_block;
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rep->cache_id = (options.block_cache ? options.block_cache->NewId() : 0);
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*table = new Table(rep);
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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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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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Table* table = reinterpret_cast<Table*>(arg);
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Cache* block_cache = table->rep_->options.block_cache;
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Block* block = NULL;
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Cache::Handle* cache_handle = NULL;
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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 != NULL) {
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char cache_key_buffer[16];
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EncodeFixed64(cache_key_buffer, table->rep_->cache_id);
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EncodeFixed64(cache_key_buffer+8, handle.offset());
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Slice key(cache_key_buffer, sizeof(cache_key_buffer));
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cache_handle = block_cache->Lookup(key);
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if (cache_handle != NULL) {
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block = reinterpret_cast<Block*>(block_cache->Value(cache_handle));
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} else {
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s = ReadBlock(table->rep_->file, options, handle, &block);
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if (s.ok() && 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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} else {
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s = ReadBlock(table->rep_->file, options, handle, &block);
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}
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}
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Iterator* iter;
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if (block != NULL) {
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iter = block->NewIterator(table->rep_->options.comparator);
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if (cache_handle == NULL) {
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iter->RegisterCleanup(&DeleteBlock, block, NULL);
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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::NewIterator(const ReadOptions& options) const {
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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);
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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 leveldb
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