2017-11-02 19:05:55 +01:00
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// 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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#ifndef ROCKSDB_LITE
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#include <mutex>
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#include <queue>
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#include <set>
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#include <string>
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#include <unordered_map>
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#include <vector>
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#include "db/db_iter.h"
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2017-12-01 08:39:56 +01:00
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#include "db/pre_release_callback.h"
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2017-11-02 19:05:55 +01:00
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#include "db/read_callback.h"
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#include "db/snapshot_checker.h"
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#include "rocksdb/db.h"
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#include "rocksdb/options.h"
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#include "rocksdb/utilities/transaction_db.h"
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2018-01-09 17:47:46 +01:00
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#include "util/string_util.h"
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2017-11-02 19:05:55 +01:00
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#include "utilities/transactions/pessimistic_transaction.h"
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#include "utilities/transactions/pessimistic_transaction_db.h"
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#include "utilities/transactions/transaction_lock_mgr.h"
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#include "utilities/transactions/write_prepared_txn.h"
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namespace rocksdb {
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2018-01-09 17:47:46 +01:00
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#define ROCKS_LOG_DETAILS(LGR, FMT, ...) \
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; // due to overhead by default skip such lines
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// ROCKS_LOG_DEBUG(LGR, FMT, ##__VA_ARGS__)
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2017-11-02 19:05:55 +01:00
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// A PessimisticTransactionDB that writes data to DB after prepare phase of 2PC.
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// In this way some data in the DB might not be committed. The DB provides
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// mechanisms to tell such data apart from committed data.
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class WritePreparedTxnDB : public PessimisticTransactionDB {
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public:
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explicit WritePreparedTxnDB(
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DB* db, const TransactionDBOptions& txn_db_options,
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size_t snapshot_cache_bits = DEF_SNAPSHOT_CACHE_BITS,
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size_t commit_cache_bits = DEF_COMMIT_CACHE_BITS)
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: PessimisticTransactionDB(db, txn_db_options),
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SNAPSHOT_CACHE_BITS(snapshot_cache_bits),
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SNAPSHOT_CACHE_SIZE(static_cast<size_t>(1ull << SNAPSHOT_CACHE_BITS)),
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COMMIT_CACHE_BITS(commit_cache_bits),
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COMMIT_CACHE_SIZE(static_cast<size_t>(1ull << COMMIT_CACHE_BITS)),
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FORMAT(COMMIT_CACHE_BITS) {
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Init(txn_db_options);
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}
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explicit WritePreparedTxnDB(
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StackableDB* db, const TransactionDBOptions& txn_db_options,
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size_t snapshot_cache_bits = DEF_SNAPSHOT_CACHE_BITS,
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size_t commit_cache_bits = DEF_COMMIT_CACHE_BITS)
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: PessimisticTransactionDB(db, txn_db_options),
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SNAPSHOT_CACHE_BITS(snapshot_cache_bits),
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SNAPSHOT_CACHE_SIZE(static_cast<size_t>(1ull << SNAPSHOT_CACHE_BITS)),
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COMMIT_CACHE_BITS(commit_cache_bits),
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COMMIT_CACHE_SIZE(static_cast<size_t>(1ull << COMMIT_CACHE_BITS)),
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FORMAT(COMMIT_CACHE_BITS) {
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Init(txn_db_options);
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}
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virtual ~WritePreparedTxnDB();
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virtual Status Initialize(
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const std::vector<size_t>& compaction_enabled_cf_indices,
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const std::vector<ColumnFamilyHandle*>& handles) override;
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Transaction* BeginTransaction(const WriteOptions& write_options,
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const TransactionOptions& txn_options,
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Transaction* old_txn) override;
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using DB::Get;
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virtual Status Get(const ReadOptions& options,
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ColumnFamilyHandle* column_family, const Slice& key,
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PinnableSlice* value) override;
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2017-11-27 17:49:30 +01:00
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using DB::MultiGet;
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virtual std::vector<Status> MultiGet(
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const ReadOptions& options,
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const std::vector<ColumnFamilyHandle*>& column_family,
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const std::vector<Slice>& keys,
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std::vector<std::string>* values) override;
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using DB::NewIterator;
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virtual Iterator* NewIterator(const ReadOptions& options,
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ColumnFamilyHandle* column_family) override;
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using DB::NewIterators;
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virtual Status NewIterators(
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const ReadOptions& options,
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const std::vector<ColumnFamilyHandle*>& column_families,
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std::vector<Iterator*>* iterators) override;
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virtual void ReleaseSnapshot(const Snapshot* snapshot) override;
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// Check whether the transaction that wrote the value with seqeunce number seq
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// is visible to the snapshot with sequence number snapshot_seq
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bool IsInSnapshot(uint64_t seq, uint64_t snapshot_seq) const;
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// Add the trasnaction with prepare sequence seq to the prepared list
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void AddPrepared(uint64_t seq);
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// Rollback a prepared txn identified with prep_seq. rollback_seq is the seq
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// with which the additional data is written to cancel the txn effect. It can
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// be used to idenitfy the snapshots that overlap with the rolled back txn.
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void RollbackPrepared(uint64_t prep_seq, uint64_t rollback_seq);
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// Add the transaction with prepare sequence prepare_seq and commit sequence
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// commit_seq to the commit map. prepare_skipped is set if the prpeare phase
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// is skipped for this commit. loop_cnt is to detect infinite loops.
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void AddCommitted(uint64_t prepare_seq, uint64_t commit_seq,
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bool prepare_skipped = false, uint8_t loop_cnt = 0);
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struct CommitEntry {
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uint64_t prep_seq;
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uint64_t commit_seq;
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CommitEntry() : prep_seq(0), commit_seq(0) {}
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CommitEntry(uint64_t ps, uint64_t cs) : prep_seq(ps), commit_seq(cs) {}
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bool operator==(const CommitEntry& rhs) const {
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return prep_seq == rhs.prep_seq && commit_seq == rhs.commit_seq;
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}
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};
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struct CommitEntry64bFormat {
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explicit CommitEntry64bFormat(size_t index_bits)
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: INDEX_BITS(index_bits),
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PREP_BITS(static_cast<size_t>(64 - PAD_BITS - INDEX_BITS)),
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COMMIT_BITS(static_cast<size_t>(64 - PREP_BITS)),
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COMMIT_FILTER(static_cast<uint64_t>((1ull << COMMIT_BITS) - 1)),
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DELTA_UPPERBOUND(static_cast<uint64_t>((1ull << COMMIT_BITS))) {}
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// Number of higher bits of a sequence number that is not used. They are
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// used to encode the value type, ...
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const size_t PAD_BITS = static_cast<size_t>(8);
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// Number of lower bits from prepare seq that can be skipped as they are
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// implied by the index of the entry in the array
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const size_t INDEX_BITS;
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// Number of bits we use to encode the prepare seq
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const size_t PREP_BITS;
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// Number of bits we use to encode the commit seq.
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const size_t COMMIT_BITS;
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// Filter to encode/decode commit seq
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const uint64_t COMMIT_FILTER;
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// The value of commit_seq - prepare_seq + 1 must be less than this bound
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const uint64_t DELTA_UPPERBOUND;
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};
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// Prepare Seq (64 bits) = PAD ... PAD PREP PREP ... PREP INDEX INDEX ...
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// INDEX Detal Seq (64 bits) = 0 0 0 0 0 0 0 0 0 0 0 0 DELTA DELTA ...
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// DELTA DELTA Encoded Value = PREP PREP .... PREP PREP DELTA DELTA
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// ... DELTA DELTA PAD: first bits of a seq that is reserved for tagging and
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// hence ignored PREP/INDEX: the used bits in a prepare seq number INDEX: the
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// bits that do not have to be encoded (will be provided externally) DELTA:
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// prep seq - commit seq + 1 Number of DELTA bits should be equal to number of
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// index bits + PADs
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struct CommitEntry64b {
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constexpr CommitEntry64b() noexcept : rep_(0) {}
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CommitEntry64b(const CommitEntry& entry, const CommitEntry64bFormat& format)
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: CommitEntry64b(entry.prep_seq, entry.commit_seq, format) {}
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CommitEntry64b(const uint64_t ps, const uint64_t cs,
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const CommitEntry64bFormat& format) {
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assert(ps < static_cast<uint64_t>(
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(1ull << (format.PREP_BITS + format.INDEX_BITS))));
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assert(ps <= cs);
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uint64_t delta = cs - ps + 1; // make initialized delta always >= 1
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// zero is reserved for uninitialized entries
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assert(0 < delta);
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assert(delta < format.DELTA_UPPERBOUND);
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if (delta >= format.DELTA_UPPERBOUND) {
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throw std::runtime_error(
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"commit_seq >> prepare_seq. The allowed distance is " +
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ToString(format.DELTA_UPPERBOUND) + " commit_seq is " +
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ToString(cs) + " prepare_seq is " + ToString(ps));
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}
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rep_ = (ps << format.PAD_BITS) & ~format.COMMIT_FILTER;
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rep_ = rep_ | delta;
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}
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// Return false if the entry is empty
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bool Parse(const uint64_t indexed_seq, CommitEntry* entry,
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const CommitEntry64bFormat& format) {
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uint64_t delta = rep_ & format.COMMIT_FILTER;
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// zero is reserved for uninitialized entries
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assert(delta < static_cast<uint64_t>((1ull << format.COMMIT_BITS)));
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if (delta == 0) {
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return false; // initialized entry would have non-zero delta
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}
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assert(indexed_seq < static_cast<uint64_t>((1ull << format.INDEX_BITS)));
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uint64_t prep_up = rep_ & ~format.COMMIT_FILTER;
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prep_up >>= format.PAD_BITS;
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const uint64_t& prep_low = indexed_seq;
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entry->prep_seq = prep_up | prep_low;
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entry->commit_seq = entry->prep_seq + delta - 1;
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return true;
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}
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private:
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uint64_t rep_;
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};
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// Struct to hold ownership of snapshot and read callback for cleanup.
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struct IteratorState;
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2018-02-06 03:32:54 +01:00
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protected:
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virtual Status VerifyCFOptions(
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const ColumnFamilyOptions& cf_options) override;
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private:
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friend class WritePreparedTransactionTest_IsInSnapshotTest_Test;
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friend class WritePreparedTransactionTest_CheckAgainstSnapshotsTest_Test;
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friend class WritePreparedTransactionTest_CommitMapTest_Test;
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2018-01-30 02:03:23 +01:00
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friend class SnapshotConcurrentAccessTest_SnapshotConcurrentAccessTest_Test;
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friend class WritePreparedTransactionTestBase;
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friend class PreparedHeap_BasicsTest_Test;
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friend class WritePreparedTxnDBMock;
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friend class WritePreparedTransactionTest_AdvanceMaxEvictedSeqBasicTest_Test;
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friend class WritePreparedTransactionTest_BasicRecoveryTest_Test;
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friend class WritePreparedTransactionTest_IsInSnapshotEmptyMapTest_Test;
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friend class WritePreparedTransactionTest_OldCommitMapGC_Test;
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friend class WritePreparedTransactionTest_RollbackTest_Test;
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void Init(const TransactionDBOptions& /* unused */);
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// A heap with the amortized O(1) complexity for erase. It uses one extra heap
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// to keep track of erased entries that are not yet on top of the main heap.
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class PreparedHeap {
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std::priority_queue<uint64_t, std::vector<uint64_t>, std::greater<uint64_t>>
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heap_;
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std::priority_queue<uint64_t, std::vector<uint64_t>, std::greater<uint64_t>>
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erased_heap_;
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public:
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bool empty() { return heap_.empty(); }
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uint64_t top() { return heap_.top(); }
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void push(uint64_t v) { heap_.push(v); }
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void pop() {
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heap_.pop();
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while (!heap_.empty() && !erased_heap_.empty() &&
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heap_.top() == erased_heap_.top()) {
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heap_.pop();
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erased_heap_.pop();
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}
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while (heap_.empty() && !erased_heap_.empty()) {
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erased_heap_.pop();
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}
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}
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void erase(uint64_t seq) {
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if (!heap_.empty()) {
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if (seq < heap_.top()) {
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// Already popped, ignore it.
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} else if (heap_.top() == seq) {
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pop();
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} else { // (heap_.top() > seq)
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// Down the heap, remember to pop it later
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erased_heap_.push(seq);
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}
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}
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}
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};
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// Get the commit entry with index indexed_seq from the commit table. It
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// returns true if such entry exists.
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bool GetCommitEntry(const uint64_t indexed_seq, CommitEntry64b* entry_64b,
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CommitEntry* entry) const;
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// Rewrite the entry with the index indexed_seq in the commit table with the
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// commit entry <prep_seq, commit_seq>. If the rewrite results into eviction,
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// sets the evicted_entry and returns true.
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bool AddCommitEntry(const uint64_t indexed_seq, const CommitEntry& new_entry,
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CommitEntry* evicted_entry);
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// Rewrite the entry with the index indexed_seq in the commit table with the
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// commit entry new_entry only if the existing entry matches the
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// expected_entry. Returns false otherwise.
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bool ExchangeCommitEntry(const uint64_t indexed_seq,
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CommitEntry64b& expected_entry,
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const CommitEntry& new_entry);
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// Increase max_evicted_seq_ from the previous value prev_max to the new
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// value. This also involves taking care of prepared txns that are not
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// committed before new_max, as well as updating the list of live snapshots at
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// the time of updating the max. Thread-safety: this function can be called
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// concurrently. The concurrent invocations of this function is equivalent to
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// a serial invocation in which the last invocation is the one with the
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// largetst new_max value.
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void AdvanceMaxEvictedSeq(SequenceNumber& prev_max, SequenceNumber& new_max);
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virtual const std::vector<SequenceNumber> GetSnapshotListFromDB(
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SequenceNumber max);
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// Will be called by the public ReleaseSnapshot method. Does the maintenance
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// internal to WritePreparedTxnDB
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void ReleaseSnapshotInternal(const SequenceNumber snap_seq);
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// Update the list of snapshots corresponding to the soon-to-be-updated
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// max_eviceted_seq_. Thread-safety: this function can be called concurrently.
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// The concurrent invocations of this function is equivalent to a serial
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// invocation in which the last invocation is the one with the largetst
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// version value.
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void UpdateSnapshots(const std::vector<SequenceNumber>& snapshots,
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const SequenceNumber& version);
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// Check an evicted entry against live snapshots to see if it should be kept
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// around or it can be safely discarded (and hence assume committed for all
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// snapshots). Thread-safety: this function can be called concurrently. If it
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// is called concurrently with multiple UpdateSnapshots, the result is the
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// same as checking the intersection of the snapshot list before updates with
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// the snapshot list of all the concurrent updates.
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void CheckAgainstSnapshots(const CommitEntry& evicted);
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// Add a new entry to old_commit_map_ if prep_seq <= snapshot_seq <
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// commit_seq. Return false if checking the next snapshot(s) is not needed.
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2017-12-13 16:52:02 +01:00
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// This is the case if none of the next snapshots could satisfy the condition.
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// next_is_larger: the next snapshot will be a larger value
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2017-11-02 19:05:55 +01:00
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bool MaybeUpdateOldCommitMap(const uint64_t& prep_seq,
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const uint64_t& commit_seq,
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const uint64_t& snapshot_seq,
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const bool next_is_larger);
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// The list of live snapshots at the last time that max_evicted_seq_ advanced.
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// The list stored into two data structures: in snapshot_cache_ that is
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// efficient for concurrent reads, and in snapshots_ if the data does not fit
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// into snapshot_cache_. The total number of snapshots in the two lists
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std::atomic<size_t> snapshots_total_ = {};
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// The list sorted in ascending order. Thread-safety for writes is provided
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// with snapshots_mutex_ and concurrent reads are safe due to std::atomic for
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// each entry. In x86_64 architecture such reads are compiled to simple read
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// instructions. 128 entries
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static const size_t DEF_SNAPSHOT_CACHE_BITS = static_cast<size_t>(7);
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const size_t SNAPSHOT_CACHE_BITS;
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const size_t SNAPSHOT_CACHE_SIZE;
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unique_ptr<std::atomic<SequenceNumber>[]> snapshot_cache_;
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// 2nd list for storing snapshots. The list sorted in ascending order.
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// Thread-safety is provided with snapshots_mutex_.
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std::vector<SequenceNumber> snapshots_;
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// The version of the latest list of snapshots. This can be used to avoid
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// rewrittiing a list that is concurrently updated with a more recent version.
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SequenceNumber snapshots_version_ = 0;
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// A heap of prepared transactions. Thread-safety is provided with
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// prepared_mutex_.
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PreparedHeap prepared_txns_;
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// 10m entry, 80MB size
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static const size_t DEF_COMMIT_CACHE_BITS = static_cast<size_t>(21);
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const size_t COMMIT_CACHE_BITS;
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const size_t COMMIT_CACHE_SIZE;
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const CommitEntry64bFormat FORMAT;
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// commit_cache_ must be initialized to zero to tell apart an empty index from
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// a filled one. Thread-safety is provided with commit_cache_mutex_.
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unique_ptr<std::atomic<CommitEntry64b>[]> commit_cache_;
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2018-01-09 17:47:46 +01:00
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// The largest evicted *commit* sequence number from the commit_cache_. If a
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// seq is smaller than max_evicted_seq_ is might or might not be present in
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// commit_cache_. So commit_cache_ must first be checked before consulting
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// with max_evicted_seq_.
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2017-11-02 19:05:55 +01:00
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std::atomic<uint64_t> max_evicted_seq_ = {};
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// Advance max_evicted_seq_ by this value each time it needs an update. The
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// larger the value, the less frequent advances we would have. We do not want
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// it to be too large either as it would cause stalls by doing too much
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// maintenance work under the lock.
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size_t INC_STEP_FOR_MAX_EVICTED = 1;
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2017-12-13 16:52:02 +01:00
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// A map from old snapshots (expected to be used by a few read-only txns) to
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// prpared sequence number of the evicted entries from commit_cache_ that
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// overlaps with such snapshot. These are the prepared sequence numbers that
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// the snapshot, to which they are mapped, cannot assume to be committed just
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// because it is no longer in the commit_cache_. The vector must be sorted
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// after each update.
|
2017-11-02 19:05:55 +01:00
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// Thread-safety is provided with old_commit_map_mutex_.
|
2017-12-13 16:52:02 +01:00
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std::map<SequenceNumber, std::vector<SequenceNumber>> old_commit_map_;
|
2017-11-02 19:05:55 +01:00
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// A set of long-running prepared transactions that are not finished by the
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// time max_evicted_seq_ advances their sequence number. This is expected to
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// be empty normally. Thread-safety is provided with prepared_mutex_.
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std::set<uint64_t> delayed_prepared_;
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// Update when delayed_prepared_.empty() changes. Expected to be true
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// normally.
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std::atomic<bool> delayed_prepared_empty_ = {true};
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// Update when old_commit_map_.empty() changes. Expected to be true normally.
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std::atomic<bool> old_commit_map_empty_ = {true};
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mutable port::RWMutex prepared_mutex_;
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mutable port::RWMutex old_commit_map_mutex_;
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mutable port::RWMutex commit_cache_mutex_;
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mutable port::RWMutex snapshots_mutex_;
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};
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class WritePreparedTxnReadCallback : public ReadCallback {
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public:
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WritePreparedTxnReadCallback(WritePreparedTxnDB* db, SequenceNumber snapshot)
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: db_(db), snapshot_(snapshot) {}
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// Will be called to see if the seq number accepted; if not it moves on to the
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// next seq number.
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virtual bool IsCommitted(SequenceNumber seq) override {
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return db_->IsInSnapshot(seq, snapshot_);
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}
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private:
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WritePreparedTxnDB* db_;
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|
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SequenceNumber snapshot_;
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};
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|
2017-12-01 08:39:56 +01:00
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class WritePreparedCommitEntryPreReleaseCallback : public PreReleaseCallback {
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public:
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// includes_data indicates that the commit also writes non-empty
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// CommitTimeWriteBatch to memtable, which needs to be committed separately.
|
2018-02-06 03:32:54 +01:00
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WritePreparedCommitEntryPreReleaseCallback(WritePreparedTxnDB* db,
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|
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DBImpl* db_impl,
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|
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SequenceNumber prep_seq,
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|
|
size_t prep_batch_cnt,
|
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|
|
size_t data_batch_cnt = 0)
|
2017-12-01 08:39:56 +01:00
|
|
|
: db_(db),
|
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|
|
db_impl_(db_impl),
|
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|
|
prep_seq_(prep_seq),
|
2018-02-06 03:32:54 +01:00
|
|
|
prep_batch_cnt_(prep_batch_cnt),
|
|
|
|
data_batch_cnt_(data_batch_cnt),
|
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|
|
includes_data_(data_batch_cnt_ > 0) {
|
|
|
|
assert((prep_batch_cnt_ > 0) != (prep_seq == kMaxSequenceNumber)); // xor
|
|
|
|
assert(prep_batch_cnt_ > 0 || data_batch_cnt_ > 0);
|
|
|
|
}
|
2017-12-01 08:39:56 +01:00
|
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|
|
2018-02-06 03:32:54 +01:00
|
|
|
virtual Status Callback(SequenceNumber commit_seq) override {
|
2017-12-18 17:03:18 +01:00
|
|
|
assert(includes_data_ || prep_seq_ != kMaxSequenceNumber);
|
2018-02-06 03:32:54 +01:00
|
|
|
const uint64_t last_commit_seq = LIKELY(data_batch_cnt_ <= 1)
|
|
|
|
? commit_seq
|
|
|
|
: commit_seq + data_batch_cnt_ - 1;
|
2017-12-18 17:03:18 +01:00
|
|
|
if (prep_seq_ != kMaxSequenceNumber) {
|
2018-02-06 03:32:54 +01:00
|
|
|
for (size_t i = 0; i < prep_batch_cnt_; i++) {
|
|
|
|
db_->AddCommitted(prep_seq_ + i, last_commit_seq);
|
|
|
|
}
|
2017-12-18 17:03:18 +01:00
|
|
|
} // else there was no prepare phase
|
2017-12-01 08:39:56 +01:00
|
|
|
if (includes_data_) {
|
2018-02-06 03:32:54 +01:00
|
|
|
assert(data_batch_cnt_);
|
2017-12-18 17:03:18 +01:00
|
|
|
// Commit the data that is accompnaied with the commit request
|
2018-01-09 17:47:46 +01:00
|
|
|
const bool PREPARE_SKIPPED = true;
|
2018-02-06 03:32:54 +01:00
|
|
|
for (size_t i = 0; i < data_batch_cnt_; i++) {
|
|
|
|
// For commit seq of each batch use the commit seq of the last batch.
|
|
|
|
// This would make debugging easier by having all the batches having
|
|
|
|
// the same sequence number.
|
|
|
|
db_->AddCommitted(commit_seq + i, last_commit_seq, PREPARE_SKIPPED);
|
|
|
|
}
|
2017-12-01 08:39:56 +01:00
|
|
|
}
|
2017-12-18 17:03:18 +01:00
|
|
|
if (db_impl_->immutable_db_options().two_write_queues) {
|
|
|
|
// Publish the sequence number. We can do that here assuming the callback
|
|
|
|
// is invoked only from one write queue, which would guarantee that the
|
|
|
|
// publish sequence numbers will be in order, i.e., once a seq is
|
|
|
|
// published all the seq prior to that are also publishable.
|
2018-02-06 03:32:54 +01:00
|
|
|
db_impl_->SetLastPublishedSequence(last_commit_seq);
|
2017-12-18 17:03:18 +01:00
|
|
|
}
|
|
|
|
// else SequenceNumber that is updated as part of the write already does the
|
|
|
|
// publishing
|
2017-12-01 08:39:56 +01:00
|
|
|
return Status::OK();
|
|
|
|
}
|
|
|
|
|
|
|
|
private:
|
|
|
|
WritePreparedTxnDB* db_;
|
|
|
|
DBImpl* db_impl_;
|
2017-12-18 17:03:18 +01:00
|
|
|
// kMaxSequenceNumber if there was no prepare phase
|
2017-12-01 08:39:56 +01:00
|
|
|
SequenceNumber prep_seq_;
|
2018-02-06 03:32:54 +01:00
|
|
|
size_t prep_batch_cnt_;
|
|
|
|
size_t data_batch_cnt_;
|
2017-12-18 17:03:18 +01:00
|
|
|
// Either because it is commit without prepare or it has a
|
|
|
|
// CommitTimeWriteBatch
|
2017-12-01 08:39:56 +01:00
|
|
|
bool includes_data_;
|
|
|
|
};
|
|
|
|
|
2017-11-02 19:05:55 +01:00
|
|
|
} // namespace rocksdb
|
|
|
|
#endif // ROCKSDB_LITE
|