df9069d23f
Summary: In this patch, try to allocate the whole iterator tree starting from DBIter from an arena 1. ArenaWrappedDBIter is created when serves as the entry point of an iterator tree, with an arena in it. 2. Add an option to create iterator from arena for following iterators: DBIter, MergingIterator, MemtableIterator, all mem table's iterators, all table reader's iterators and two level iterator. 3. MergeIteratorBuilder is created to incrementally build the tree of internal iterators. It is passed to mem table list and version set and add iterators to it. Limitations: (1) Only DB::NewIterator() without tailing uses the arena. Other cases, including readonly DB and compactions are still from malloc (2) Two level iterator itself is allocated in arena, but not iterators inside it. Test Plan: make all check Reviewers: ljin, haobo Reviewed By: haobo Subscribers: leveldb, dhruba, yhchiang, igor Differential Revision: https://reviews.facebook.net/D18513
72 lines
3.1 KiB
C++
72 lines
3.1 KiB
C++
// Copyright (c) 2013, 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 <memory>
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namespace rocksdb {
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class Iterator;
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struct ParsedInternalKey;
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class Slice;
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class Arena;
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struct ReadOptions;
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struct TableProperties;
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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 TableReader {
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public:
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virtual ~TableReader() {}
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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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// arena: If not null, the arena needs to be used to allocate the Iterator.
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// When destroying the iterator, the caller will not call "delete"
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// but Iterator::~Iterator() directly. The destructor needs to destroy
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// all the states but those allocated in arena.
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virtual Iterator* NewIterator(const ReadOptions&, Arena* arena = nullptr) = 0;
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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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virtual uint64_t ApproximateOffsetOf(const Slice& key) = 0;
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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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virtual void SetupForCompaction() = 0;
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virtual std::shared_ptr<const TableProperties> GetTableProperties() const = 0;
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// Calls (*result_handler)(handle_context, ...) repeatedly, starting with
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// the entry found after a call to Seek(key), until result_handler returns
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// false, where k is the actual internal key for a row found and v as the
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// value of the key. didIO is true if I/O is involved in the operation. May
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// not make such a call if filter policy says that key is not present.
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//
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// mark_key_may_exist_handler needs to be called when it is configured to be
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// memory only and the key is not found in the block cache, with
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// the parameter to be handle_context.
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//
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// readOptions is the options for the read
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// key is the key to search for
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virtual Status Get(
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const ReadOptions& readOptions, const Slice& key, void* handle_context,
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bool (*result_handler)(void* arg, const ParsedInternalKey& k,
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const Slice& v, bool didIO),
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void (*mark_key_may_exist_handler)(void* handle_context) = nullptr) = 0;
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};
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} // namespace rocksdb
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