5b825d6964
Summary: liveness of the statistics object is already ensured by the shared pointer in DB options. There's no reason to pass again shared pointer among internal functions. Raw pointer is sufficient and efficient. Test Plan: make check Reviewers: dhruba, MarkCallaghan, igor Reviewed By: dhruba CC: leveldb, reconnect.grayhat Differential Revision: https://reviews.facebook.net/D14289
103 lines
4.0 KiB
C++
103 lines
4.0 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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#ifndef MERGE_HELPER_H
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#define MERGE_HELPER_H
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#include "db/dbformat.h"
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#include "rocksdb/slice.h"
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#include <string>
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#include <deque>
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namespace rocksdb {
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class Comparator;
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class Iterator;
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class Logger;
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class MergeOperator;
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class Statistics;
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class MergeHelper {
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public:
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MergeHelper(const Comparator* user_comparator,
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const MergeOperator* user_merge_operator,
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Logger* logger,
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bool assert_valid_internal_key)
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: user_comparator_(user_comparator),
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user_merge_operator_(user_merge_operator),
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logger_(logger),
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assert_valid_internal_key_(assert_valid_internal_key),
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keys_(),
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operands_(),
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success_(false) {}
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// Merge entries until we hit
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// - a corrupted key
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// - a Put/Delete,
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// - a different user key,
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// - a specific sequence number (snapshot boundary),
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// or - the end of iteration
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// iter: (IN) points to the first merge type entry
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// (OUT) points to the first entry not included in the merge process
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// stop_before: (IN) a sequence number that merge should not cross.
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// 0 means no restriction
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// at_bottom: (IN) true if the iterator covers the bottem level, which means
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// we could reach the start of the history of this user key.
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void MergeUntil(Iterator* iter, SequenceNumber stop_before = 0,
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bool at_bottom = false, Statistics* stats = nullptr);
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// Query the merge result
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// These are valid until the next MergeUntil call
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// If the merging was successful:
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// - IsSuccess() will be true
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// - key() will have the latest sequence number of the merges.
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// The type will be Put or Merge. See IMPORTANT 1 note, below.
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// - value() will be the result of merging all the operands together
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// - The user should ignore keys() and values().
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//
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// IMPORTANT 1: the key type could change after the MergeUntil call.
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// Put/Delete + Merge + ... + Merge => Put
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// Merge + ... + Merge => Merge
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//
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// If the merge operator is not associative, and if a Put/Delete is not found
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// then the merging will be unsuccessful. In this case:
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// - IsSuccess() will be false
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// - keys() contains the list of internal keys seen in order of iteration.
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// - values() contains the list of values (merges) seen in the same order.
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// values() is parallel to keys() so that the first entry in
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// keys() is the key associated with the first entry in values()
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// and so on. These lists will be the same length.
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// All of these pairs will be merges over the same user key.
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// See IMPORTANT 2 note below.
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// - The user should ignore key() and value().
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//
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// IMPORTANT 2: The entries were traversed in order from BACK to FRONT.
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// So keys().back() was the first key seen by iterator.
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// TODO: Re-style this comment to be like the first one
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bool IsSuccess() { return success_; }
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Slice key() { assert(success_); return Slice(keys_.back()); }
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Slice value() { assert(success_); return Slice(operands_.back()); }
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const std::deque<std::string>& keys() { assert(!success_); return keys_; }
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const std::deque<std::string>& values() {
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assert(!success_); return operands_;
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}
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private:
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const Comparator* user_comparator_;
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const MergeOperator* user_merge_operator_;
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Logger* logger_;
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bool assert_valid_internal_key_; // enforce no internal key corruption?
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// the scratch area that holds the result of MergeUntil
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// valid up to the next MergeUntil call
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std::deque<std::string> keys_; // Keeps track of the sequence of keys seen
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std::deque<std::string> operands_; // Parallel with keys_; stores the values
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bool success_;
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};
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} // namespace rocksdb
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#endif
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