235 lines
9.5 KiB
C++
235 lines
9.5 KiB
C++
// Copyright (c) 2011-present, 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 <stdint.h>
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#include <memory>
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#include <utility>
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#include <string>
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#include "rocksdb/options.h"
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#include "rocksdb/statistics.h"
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#include "rocksdb/status.h"
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#include "rocksdb/table.h"
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#include "table/table_reader.h"
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#include "table/table_properties_internal.h"
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#include "util/coding.h"
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#include "util/file_reader_writer.h"
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namespace rocksdb {
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class Block;
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class BlockIter;
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class BlockHandle;
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class Cache;
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class FilterBlockReader;
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class BlockBasedFilterBlockReader;
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class FullFilterBlockReader;
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class Footer;
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class InternalKeyComparator;
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class Iterator;
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class RandomAccessFile;
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class TableCache;
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class TableReader;
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class WritableFile;
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struct BlockBasedTableOptions;
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struct EnvOptions;
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struct ReadOptions;
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class GetContext;
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class InternalIterator;
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using std::unique_ptr;
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// A Table is a sorted map from strings to strings. Tables are
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// immutable and persistent. A Table may be safely accessed from
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// multiple threads without external synchronization.
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class BlockBasedTable : public TableReader {
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public:
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static const std::string kFilterBlockPrefix;
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static const std::string kFullFilterBlockPrefix;
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// Attempt to open the table that is stored in bytes [0..file_size)
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// of "file", and read the metadata entries necessary to allow
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// retrieving data from the table.
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//
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// If successful, returns ok and sets "*table_reader" to the newly opened
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// table. The client should delete "*table_reader" when no longer needed.
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// If there was an error while initializing the table, sets "*table_reader"
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// to nullptr and returns a non-ok status.
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//
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// @param file must remain live while this Table is in use.
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// @param prefetch_index_and_filter can be used to disable prefetching of
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// index and filter blocks at startup
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// @param skip_filters Disables loading/accessing the filter block. Overrides
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// prefetch_index_and_filter, so filter will be skipped if both are set.
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static Status Open(const ImmutableCFOptions& ioptions,
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const EnvOptions& env_options,
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const BlockBasedTableOptions& table_options,
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const InternalKeyComparator& internal_key_comparator,
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unique_ptr<RandomAccessFileReader>&& file,
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uint64_t file_size, unique_ptr<TableReader>* table_reader,
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bool prefetch_index_and_filter = true,
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bool skip_filters = false);
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bool PrefixMayMatch(const Slice& internal_key);
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// Returns a new iterator over the table contents.
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// The result of NewIterator() is initially invalid (caller must
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// call one of the Seek methods on the iterator before using it).
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// @param skip_filters Disables loading/accessing the filter block
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InternalIterator* NewIterator(const ReadOptions&, Arena* arena = nullptr,
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bool skip_filters = false) override;
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// @param skip_filters Disables loading/accessing the filter block
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Status Get(const ReadOptions& readOptions, const Slice& key,
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GetContext* get_context, bool skip_filters = false) override;
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// Pre-fetch the disk blocks that correspond to the key range specified by
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// (kbegin, kend). The call will return return error status in the event of
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// IO or iteration error.
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Status Prefetch(const Slice* begin, const Slice* end) override;
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// Given a key, return an approximate byte offset in the file where
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// the data for that key begins (or would begin if the key were
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// present in the file). The returned value is in terms of file
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// bytes, and so includes effects like compression of the underlying data.
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// E.g., the approximate offset of the last key in the table will
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// be close to the file length.
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uint64_t ApproximateOffsetOf(const Slice& key) override;
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// Returns true if the block for the specified key is in cache.
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// REQUIRES: key is in this table && block cache enabled
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bool TEST_KeyInCache(const ReadOptions& options, const Slice& key);
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// Set up the table for Compaction. Might change some parameters with
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// posix_fadvise
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void SetupForCompaction() override;
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std::shared_ptr<const TableProperties> GetTableProperties() const override;
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size_t ApproximateMemoryUsage() const override;
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// convert SST file to a human readable form
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Status DumpTable(WritableFile* out_file) override;
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~BlockBasedTable();
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bool TEST_filter_block_preloaded() const;
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bool TEST_index_reader_preloaded() const;
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// Implementation of IndexReader will be exposed to internal cc file only.
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class IndexReader;
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private:
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template <class TValue>
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struct CachableEntry;
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struct Rep;
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Rep* rep_;
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bool compaction_optimized_;
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class BlockEntryIteratorState;
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// input_iter: if it is not null, update this one and return it as Iterator
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static InternalIterator* NewDataBlockIterator(
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Rep* rep, const ReadOptions& ro, const Slice& index_value,
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BlockIter* input_iter = nullptr);
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// For the following two functions:
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// if `no_io == true`, we will not try to read filter/index from sst file
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// were they not present in cache yet.
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CachableEntry<FilterBlockReader> GetFilter(bool no_io = false) const;
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// Get the iterator from the index reader.
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// If input_iter is not set, return new Iterator
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// If input_iter is set, update it and return it as Iterator
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//
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// Note: ErrorIterator with Status::Incomplete shall be returned if all the
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// following conditions are met:
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// 1. We enabled table_options.cache_index_and_filter_blocks.
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// 2. index is not present in block cache.
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// 3. We disallowed any io to be performed, that is, read_options ==
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// kBlockCacheTier
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InternalIterator* NewIndexIterator(const ReadOptions& read_options,
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BlockIter* input_iter = nullptr);
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// Read block cache from block caches (if set): block_cache and
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// block_cache_compressed.
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// On success, Status::OK with be returned and @block will be populated with
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// pointer to the block as well as its block handle.
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static Status GetDataBlockFromCache(
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const Slice& block_cache_key, const Slice& compressed_block_cache_key,
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Cache* block_cache, Cache* block_cache_compressed, Statistics* statistics,
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const ReadOptions& read_options,
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BlockBasedTable::CachableEntry<Block>* block, uint32_t format_version);
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// Put a raw block (maybe compressed) to the corresponding block caches.
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// This method will perform decompression against raw_block if needed and then
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// populate the block caches.
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// On success, Status::OK will be returned; also @block will be populated with
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// uncompressed block and its cache handle.
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//
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// REQUIRES: raw_block is heap-allocated. PutDataBlockToCache() will be
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// responsible for releasing its memory if error occurs.
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static Status PutDataBlockToCache(
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const Slice& block_cache_key, const Slice& compressed_block_cache_key,
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Cache* block_cache, Cache* block_cache_compressed,
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const ReadOptions& read_options, Statistics* statistics,
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CachableEntry<Block>* block, Block* raw_block, uint32_t format_version);
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// Calls (*handle_result)(arg, ...) repeatedly, starting with the entry found
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// after a call to Seek(key), until handle_result returns false.
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// May not make such a call if filter policy says that key is not present.
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friend class TableCache;
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friend class BlockBasedTableBuilder;
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void ReadMeta(const Footer& footer);
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// Create a index reader based on the index type stored in the table.
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// Optionally, user can pass a preloaded meta_index_iter for the index that
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// need to access extra meta blocks for index construction. This parameter
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// helps avoid re-reading meta index block if caller already created one.
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Status CreateIndexReader(
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IndexReader** index_reader,
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InternalIterator* preloaded_meta_index_iter = nullptr);
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bool FullFilterKeyMayMatch(FilterBlockReader* filter,
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const Slice& user_key) const;
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// Read the meta block from sst.
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static Status ReadMetaBlock(Rep* rep, std::unique_ptr<Block>* meta_block,
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std::unique_ptr<InternalIterator>* iter);
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// Create the filter from the filter block.
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static FilterBlockReader* ReadFilter(Rep* rep, size_t* filter_size = nullptr);
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static void SetupCacheKeyPrefix(Rep* rep, uint64_t file_size);
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explicit BlockBasedTable(Rep* rep)
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: rep_(rep), compaction_optimized_(false) {}
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// Generate a cache key prefix from the file
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static void GenerateCachePrefix(Cache* cc,
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RandomAccessFile* file, char* buffer, size_t* size);
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static void GenerateCachePrefix(Cache* cc,
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WritableFile* file, char* buffer, size_t* size);
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// The longest prefix of the cache key used to identify blocks.
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// For Posix files the unique ID is three varints.
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static const size_t kMaxCacheKeyPrefixSize = kMaxVarint64Length*3+1;
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// Helper functions for DumpTable()
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Status DumpIndexBlock(WritableFile* out_file);
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Status DumpDataBlocks(WritableFile* out_file);
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// No copying allowed
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explicit BlockBasedTable(const TableReader&) = delete;
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void operator=(const TableReader&) = delete;
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};
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} // namespace rocksdb
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