fc0c399d2e
Summary: If ReadOptions.non_blocking_io is set to true, then KeyMayExists and Iterators will return data that is cached in RAM. If the Iterator needs to do IO from storage to serve the data, then the Iterator.status() will return Status::IsRetry(). Test Plan: Enhanced unit test DBTest.KeyMayExist to detect if there were are IOs issues from storage. Added DBTest.NonBlockingIteration to verify nonblocking Iterations. Reviewers: emayanke, haobo Reviewed By: haobo CC: leveldb Maniphest Tasks: T63 Differential Revision: https://reviews.facebook.net/D12531
108 lines
3.8 KiB
C++
108 lines
3.8 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 "rocksdb/iterator.h"
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#include "rocksdb/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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bool PrefixMayMatch(const Slice& internal_prefix) const;
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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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// Set up the table for Compaction. Might change some parameters with
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// posix_fadvise
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void SetupForCompaction();
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private:
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struct Rep;
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Rep* rep_;
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bool compaction_optimized_;
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explicit Table(Rep* rep) : compaction_optimized_(false) { 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, bool for_compaction = false);
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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 (*mark_key_may_exist)(void*) = nullptr);
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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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