2014cdf2d0
Summary: Now if we have iterate_upper_bound set, we continue read until get a key >= upper_bound. For a lot of cases that neighboring data blocks have a user key gap between them, our index key will be a user key in the middle to get a shorter size. For example, if we have blocks: [a b c d][f g h] Then the index key for the first block will be 'e'. then if upper bound is any key between 'd' and 'e', for example, d1, d2, ..., d99999999999, we don't have to read the second block and also know that we have done our iteration by reaching the last key that smaller the upper bound already. This diff can reduce RA in most cases. Closes https://github.com/facebook/rocksdb/pull/2239 Differential Revision: D4990693 Pulled By: lightmark fbshipit-source-id: ab30ea2e3c6edf3fddd5efed3c34fcf7739827ff
54 lines
2.2 KiB
C++
54 lines
2.2 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 "rocksdb/iterator.h"
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#include "rocksdb/env.h"
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#include "table/iterator_wrapper.h"
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namespace rocksdb {
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struct ReadOptions;
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class InternalKeyComparator;
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class Arena;
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struct TwoLevelIteratorState {
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explicit TwoLevelIteratorState(bool _check_prefix_may_match)
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: check_prefix_may_match(_check_prefix_may_match) {}
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virtual ~TwoLevelIteratorState() {}
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virtual InternalIterator* NewSecondaryIterator(const Slice& handle) = 0;
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virtual bool PrefixMayMatch(const Slice& internal_key) = 0;
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virtual bool KeyReachedUpperBound(const Slice& internal_key) = 0;
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// If call PrefixMayMatch()
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bool check_prefix_may_match;
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};
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// Return a new two level iterator. A two-level iterator contains an
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// index iterator whose values point to a sequence of blocks where
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// each block is itself a sequence of key,value pairs. The returned
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// two-level iterator yields the concatenation of all key/value pairs
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// in the sequence of blocks. Takes ownership of "index_iter" and
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// will delete it when no longer needed.
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//
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// Uses a supplied function to convert an index_iter value into
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// an iterator over the contents of the corresponding block.
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// arena: If not null, the arena is used to allocate the Iterator.
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// When destroying the iterator, the destructor will destroy
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// all the states but those allocated in arena.
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// need_free_iter_and_state: free `state` and `first_level_iter` if
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// true. Otherwise, just call destructor.
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extern InternalIterator* NewTwoLevelIterator(
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TwoLevelIteratorState* state, InternalIterator* first_level_iter,
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Arena* arena = nullptr, bool need_free_iter_and_state = true);
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} // namespace rocksdb
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