ab8d2f6ab2
Summary: Current posix advice implementation ties up the access pattern hint with the creation of a file. It is not possible to apply different advice for different access (random get vs compaction read), without keeping two open files for the same table. This patch extended the RandomeAccessFile interface to accept new access hint at anytime. Particularly, we are able to set different access hint on the same table file based on when/how the file is used. Two options are added to set the access hint, after the file is first opened and after the file is being compacted. Test Plan: make check; db_stress; db_bench Reviewers: dhruba Reviewed By: dhruba CC: MarkCallaghan, leveldb Differential Revision: https://reviews.facebook.net/D10905
103 lines
3.6 KiB
C++
103 lines
3.6 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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#ifndef STORAGE_LEVELDB_INCLUDE_TABLE_H_
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#define STORAGE_LEVELDB_INCLUDE_TABLE_H_
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#include <memory>
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#include <stdint.h>
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#include "leveldb/iterator.h"
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#include "leveldb/env.h"
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namespace leveldb {
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class Block;
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class BlockHandle;
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class Footer;
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struct Options;
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class RandomAccessFile;
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struct ReadOptions;
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class TableCache;
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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 Table {
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public:
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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" to the newly opened
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// table. The client should delete "*table" when no longer needed.
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// If there was an error while initializing the table, sets "*table"
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// to nullptr and returns a non-ok status. Does not take ownership of
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// "*source", but the client must ensure that "source" remains live
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// for the duration of the returned table's lifetime.
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//
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// *file must remain live while this Table is in use.
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static Status 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 file_size,
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unique_ptr<Table>* table);
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~Table();
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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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Iterator* NewIterator(const ReadOptions&) const;
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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) const;
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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.
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bool TEST_KeyInCache(const ReadOptions& options, const Slice& key);
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void SetAccessHintForCompaction();
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private:
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struct Rep;
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Rep* rep_;
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explicit Table(Rep* rep) { rep_ = rep; }
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static Iterator* BlockReader(void*, const ReadOptions&,
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const EnvOptions& soptions, const Slice&,
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bool for_compaction);
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static Iterator* BlockReader(void*, const ReadOptions&, const Slice&,
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bool* didIO);
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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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Status InternalGet(
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const ReadOptions&, const Slice& key,
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void* arg,
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bool (*handle_result)(void* arg, const Slice& k, const Slice& v, bool));
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void ReadMeta(const Footer& footer);
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void ReadFilter(const Slice& filter_handle_value);
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static void SetupCacheKeyPrefix(Rep* rep);
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// No copying allowed
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Table(const Table&);
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void operator=(const Table&);
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};
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} // namespace leveldb
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#endif // STORAGE_LEVELDB_INCLUDE_TABLE_H_
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