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a661c0d208
Summary: The read path includes a callback function, ReadCallback, which would eventually calls IsInSnapshot to figure if a particular seq is in the reading snapshot or not. This callback is virtual, which adds the cost of multiple virtual function call to each read. The first few checks in IsInSnapshot, however, are quite trivial and take care of majority of the cases. The patch moves those to a non-virtual function in the the parent class, ReadCallback, to lower the virtual callback cost. Pull Request resolved: https://github.com/facebook/rocksdb/pull/5018 Differential Revision: D14226562 Pulled By: maysamyabandeh fbshipit-source-id: 6feed5b34f3b082e52092c5ef143e29b49c46b44
53 lines
1.7 KiB
C++
53 lines
1.7 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include "rocksdb/types.h"
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namespace rocksdb {
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class ReadCallback {
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public:
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ReadCallback() {}
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ReadCallback(SequenceNumber snapshot) : snapshot_(snapshot) {}
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ReadCallback(SequenceNumber snapshot, SequenceNumber min_uncommitted)
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: snapshot_(snapshot), min_uncommitted_(min_uncommitted) {}
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virtual ~ReadCallback() {}
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// Will be called to see if the seq number visible; if not it moves on to
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// the next seq number.
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virtual bool IsVisibleFullCheck(SequenceNumber seq) = 0;
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inline bool IsVisible(SequenceNumber seq) {
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if (seq == 0 || seq < min_uncommitted_) {
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assert(seq <= snapshot_);
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return true;
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} else if (snapshot_ < seq) {
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return false;
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} else {
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return IsVisibleFullCheck(seq);
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}
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}
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// This is called to determine the maximum visible sequence number for the
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// current transaction for read-your-own-write semantics. This is so that
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// for write unprepared, we will not skip keys that are written by the
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// current transaction with the seek to snapshot optimization.
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//
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// For other uses, this returns zero, meaning that the current snapshot
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// sequence number is the maximum visible sequence number.
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inline virtual SequenceNumber MaxUnpreparedSequenceNumber() { return 0; };
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protected:
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// The snapshot at which the read is performed.
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const SequenceNumber snapshot_ = kMaxSequenceNumber;
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// Any seq less than min_uncommitted_ is committed.
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const SequenceNumber min_uncommitted_ = 0;
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};
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} // namespace rocksdb
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