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-rw-r--r--src/rocksdb/db/read_callback.h54
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diff --git a/src/rocksdb/db/read_callback.h b/src/rocksdb/db/read_callback.h
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+// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
+// This source code is licensed under both the GPLv2 (found in the
+// COPYING file in the root directory) and Apache 2.0 License
+// (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include "db/dbformat.h"
+#include "rocksdb/types.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class ReadCallback {
+ public:
+ explicit ReadCallback(SequenceNumber last_visible_seq)
+ : max_visible_seq_(last_visible_seq) {}
+ ReadCallback(SequenceNumber last_visible_seq, SequenceNumber min_uncommitted)
+ : max_visible_seq_(last_visible_seq), min_uncommitted_(min_uncommitted) {}
+
+ virtual ~ReadCallback() {}
+
+ // Will be called to see if the seq number visible; if not it moves on to
+ // the next seq number.
+ virtual bool IsVisibleFullCheck(SequenceNumber seq) = 0;
+
+ inline bool IsVisible(SequenceNumber seq) {
+ assert(min_uncommitted_ > 0);
+ assert(min_uncommitted_ >= kMinUnCommittedSeq);
+ if (seq < min_uncommitted_) { // handles seq == 0 as well
+ assert(seq <= max_visible_seq_);
+ return true;
+ } else if (max_visible_seq_ < seq) {
+ assert(seq != 0);
+ return false;
+ } else {
+ assert(seq != 0); // already handled in the first if-then clause
+ return IsVisibleFullCheck(seq);
+ }
+ }
+
+ inline SequenceNumber max_visible_seq() { return max_visible_seq_; }
+
+ // Refresh to a more recent visible seq
+ virtual void Refresh(SequenceNumber seq) { max_visible_seq_ = seq; }
+
+ protected:
+ // The max visible seq, it is usually the snapshot but could be larger if
+ // transaction has its own writes written to db.
+ SequenceNumber max_visible_seq_ = kMaxSequenceNumber;
+ // Any seq less than min_uncommitted_ is committed.
+ const SequenceNumber min_uncommitted_ = kMinUnCommittedSeq;
+};
+
+} // namespace ROCKSDB_NAMESPACE