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Diffstat (limited to '')
| -rw-r--r-- | src/rocksdb/db/db_iter.cc | 1592 |
1 files changed, 1592 insertions, 0 deletions
diff --git a/src/rocksdb/db/db_iter.cc b/src/rocksdb/db/db_iter.cc new file mode 100644 index 00000000..541a5fbe --- /dev/null +++ b/src/rocksdb/db/db_iter.cc @@ -0,0 +1,1592 @@ +// 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). +// +// Copyright (c) 2011 The LevelDB Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. See the AUTHORS file for names of contributors. + +#include "db/db_iter.h" +#include <string> +#include <iostream> +#include <limits> + +#include "db/dbformat.h" +#include "db/merge_context.h" +#include "db/merge_helper.h" +#include "db/pinned_iterators_manager.h" +#include "monitoring/perf_context_imp.h" +#include "rocksdb/env.h" +#include "rocksdb/iterator.h" +#include "rocksdb/merge_operator.h" +#include "rocksdb/options.h" +#include "table/internal_iterator.h" +#include "util/arena.h" +#include "util/filename.h" +#include "util/logging.h" +#include "util/mutexlock.h" +#include "util/string_util.h" +#include "util/trace_replay.h" +#include "util/user_comparator_wrapper.h" + +namespace rocksdb { + +#if 0 +static void DumpInternalIter(Iterator* iter) { + for (iter->SeekToFirst(); iter->Valid(); iter->Next()) { + ParsedInternalKey k; + if (!ParseInternalKey(iter->key(), &k)) { + fprintf(stderr, "Corrupt '%s'\n", EscapeString(iter->key()).c_str()); + } else { + fprintf(stderr, "@ '%s'\n", k.DebugString().c_str()); + } + } +} +#endif + +// Memtables and sstables that make the DB representation contain +// (userkey,seq,type) => uservalue entries. DBIter +// combines multiple entries for the same userkey found in the DB +// representation into a single entry while accounting for sequence +// numbers, deletion markers, overwrites, etc. +class DBIter final: public Iterator { + public: + // The following is grossly complicated. TODO: clean it up + // Which direction is the iterator currently moving? + // (1) When moving forward: + // (1a) if current_entry_is_merged_ = false, the internal iterator is + // positioned at the exact entry that yields this->key(), this->value() + // (1b) if current_entry_is_merged_ = true, the internal iterator is + // positioned immediately after the last entry that contributed to the + // current this->value(). That entry may or may not have key equal to + // this->key(). + // (2) When moving backwards, the internal iterator is positioned + // just before all entries whose user key == this->key(). + enum Direction { + kForward, + kReverse + }; + + // LocalStatistics contain Statistics counters that will be aggregated per + // each iterator instance and then will be sent to the global statistics when + // the iterator is destroyed. + // + // The purpose of this approach is to avoid perf regression happening + // when multiple threads bump the atomic counters from a DBIter::Next(). + struct LocalStatistics { + explicit LocalStatistics() { ResetCounters(); } + + void ResetCounters() { + next_count_ = 0; + next_found_count_ = 0; + prev_count_ = 0; + prev_found_count_ = 0; + bytes_read_ = 0; + skip_count_ = 0; + } + + void BumpGlobalStatistics(Statistics* global_statistics) { + RecordTick(global_statistics, NUMBER_DB_NEXT, next_count_); + RecordTick(global_statistics, NUMBER_DB_NEXT_FOUND, next_found_count_); + RecordTick(global_statistics, NUMBER_DB_PREV, prev_count_); + RecordTick(global_statistics, NUMBER_DB_PREV_FOUND, prev_found_count_); + RecordTick(global_statistics, ITER_BYTES_READ, bytes_read_); + RecordTick(global_statistics, NUMBER_ITER_SKIP, skip_count_); + PERF_COUNTER_ADD(iter_read_bytes, bytes_read_); + ResetCounters(); + } + + // Map to Tickers::NUMBER_DB_NEXT + uint64_t next_count_; + // Map to Tickers::NUMBER_DB_NEXT_FOUND + uint64_t next_found_count_; + // Map to Tickers::NUMBER_DB_PREV + uint64_t prev_count_; + // Map to Tickers::NUMBER_DB_PREV_FOUND + uint64_t prev_found_count_; + // Map to Tickers::ITER_BYTES_READ + uint64_t bytes_read_; + // Map to Tickers::NUMBER_ITER_SKIP + uint64_t skip_count_; + }; + + DBIter(Env* _env, const ReadOptions& read_options, + const ImmutableCFOptions& cf_options, + const MutableCFOptions& mutable_cf_options, const Comparator* cmp, + InternalIterator* iter, SequenceNumber s, bool arena_mode, + uint64_t max_sequential_skip_in_iterations, + ReadCallback* read_callback, DBImpl* db_impl, ColumnFamilyData* cfd, + bool allow_blob) + : env_(_env), + logger_(cf_options.info_log), + user_comparator_(cmp), + merge_operator_(cf_options.merge_operator), + iter_(iter), + read_callback_(read_callback), + sequence_(s), + statistics_(cf_options.statistics), + num_internal_keys_skipped_(0), + iterate_lower_bound_(read_options.iterate_lower_bound), + iterate_upper_bound_(read_options.iterate_upper_bound), + direction_(kForward), + valid_(false), + current_entry_is_merged_(false), + prefix_same_as_start_(read_options.prefix_same_as_start), + pin_thru_lifetime_(read_options.pin_data), + total_order_seek_(read_options.total_order_seek), + allow_blob_(allow_blob), + is_blob_(false), + arena_mode_(arena_mode), + range_del_agg_(&cf_options.internal_comparator, s), + db_impl_(db_impl), + cfd_(cfd), + start_seqnum_(read_options.iter_start_seqnum) { + RecordTick(statistics_, NO_ITERATOR_CREATED); + prefix_extractor_ = mutable_cf_options.prefix_extractor.get(); + max_skip_ = max_sequential_skip_in_iterations; + max_skippable_internal_keys_ = read_options.max_skippable_internal_keys; + if (pin_thru_lifetime_) { + pinned_iters_mgr_.StartPinning(); + } + if (iter_) { + iter_->SetPinnedItersMgr(&pinned_iters_mgr_); + } + } + ~DBIter() override { + // Release pinned data if any + if (pinned_iters_mgr_.PinningEnabled()) { + pinned_iters_mgr_.ReleasePinnedData(); + } + RecordTick(statistics_, NO_ITERATOR_DELETED); + ResetInternalKeysSkippedCounter(); + local_stats_.BumpGlobalStatistics(statistics_); + if (!arena_mode_) { + delete iter_; + } else { + iter_->~InternalIterator(); + } + } + virtual void SetIter(InternalIterator* iter) { + assert(iter_ == nullptr); + iter_ = iter; + iter_->SetPinnedItersMgr(&pinned_iters_mgr_); + } + virtual ReadRangeDelAggregator* GetRangeDelAggregator() { + return &range_del_agg_; + } + + bool Valid() const override { return valid_; } + Slice key() const override { + assert(valid_); + if(start_seqnum_ > 0) { + return saved_key_.GetInternalKey(); + } else { + return saved_key_.GetUserKey(); + } + } + Slice value() const override { + assert(valid_); + if (current_entry_is_merged_) { + // If pinned_value_ is set then the result of merge operator is one of + // the merge operands and we should return it. + return pinned_value_.data() ? pinned_value_ : saved_value_; + } else if (direction_ == kReverse) { + return pinned_value_; + } else { + return iter_->value(); + } + } + Status status() const override { + if (status_.ok()) { + return iter_->status(); + } else { + assert(!valid_); + return status_; + } + } + bool IsBlob() const { + assert(valid_ && (allow_blob_ || !is_blob_)); + return is_blob_; + } + + Status GetProperty(std::string prop_name, std::string* prop) override { + if (prop == nullptr) { + return Status::InvalidArgument("prop is nullptr"); + } + if (prop_name == "rocksdb.iterator.super-version-number") { + // First try to pass the value returned from inner iterator. + return iter_->GetProperty(prop_name, prop); + } else if (prop_name == "rocksdb.iterator.is-key-pinned") { + if (valid_) { + *prop = (pin_thru_lifetime_ && saved_key_.IsKeyPinned()) ? "1" : "0"; + } else { + *prop = "Iterator is not valid."; + } + return Status::OK(); + } else if (prop_name == "rocksdb.iterator.internal-key") { + *prop = saved_key_.GetUserKey().ToString(); + return Status::OK(); + } + return Status::InvalidArgument("Unidentified property."); + } + + void Next() override; + void Prev() override; + void Seek(const Slice& target) override; + void SeekForPrev(const Slice& target) override; + void SeekToFirst() override; + void SeekToLast() override; + Env* env() { return env_; } + void set_sequence(uint64_t s) { + sequence_ = s; + if (read_callback_) { + read_callback_->Refresh(s); + } + } + void set_valid(bool v) { valid_ = v; } + + private: + // For all methods in this block: + // PRE: iter_->Valid() && status_.ok() + // Return false if there was an error, and status() is non-ok, valid_ = false; + // in this case callers would usually stop what they were doing and return. + bool ReverseToForward(); + bool ReverseToBackward(); + bool FindValueForCurrentKey(); + bool FindValueForCurrentKeyUsingSeek(); + bool FindUserKeyBeforeSavedKey(); + inline bool FindNextUserEntry(bool skipping, bool prefix_check); + bool FindNextUserEntryInternal(bool skipping, bool prefix_check); + bool ParseKey(ParsedInternalKey* key); + bool MergeValuesNewToOld(); + + void PrevInternal(); + bool TooManyInternalKeysSkipped(bool increment = true); + inline bool IsVisible(SequenceNumber sequence); + + // CanReseekToSkip() returns whether the iterator can use the optimization + // where it reseek by sequence number to get the next key when there are too + // many versions. This is disabled for write unprepared because seeking to + // sequence number does not guarantee that it is visible. + inline bool CanReseekToSkip(); + + // Temporarily pin the blocks that we encounter until ReleaseTempPinnedData() + // is called + void TempPinData() { + if (!pin_thru_lifetime_) { + pinned_iters_mgr_.StartPinning(); + } + } + + // Release blocks pinned by TempPinData() + void ReleaseTempPinnedData() { + if (!pin_thru_lifetime_ && pinned_iters_mgr_.PinningEnabled()) { + pinned_iters_mgr_.ReleasePinnedData(); + } + } + + inline void ClearSavedValue() { + if (saved_value_.capacity() > 1048576) { + std::string empty; + swap(empty, saved_value_); + } else { + saved_value_.clear(); + } + } + + inline void ResetInternalKeysSkippedCounter() { + local_stats_.skip_count_ += num_internal_keys_skipped_; + if (valid_) { + local_stats_.skip_count_--; + } + num_internal_keys_skipped_ = 0; + } + + const SliceTransform* prefix_extractor_; + Env* const env_; + Logger* logger_; + UserComparatorWrapper user_comparator_; + const MergeOperator* const merge_operator_; + InternalIterator* iter_; + ReadCallback* read_callback_; + // Max visible sequence number. It is normally the snapshot seq unless we have + // uncommitted data in db as in WriteUnCommitted. + SequenceNumber sequence_; + + IterKey saved_key_; + // Reusable internal key data structure. This is only used inside one function + // and should not be used across functions. Reusing this object can reduce + // overhead of calling construction of the function if creating it each time. + ParsedInternalKey ikey_; + std::string saved_value_; + Slice pinned_value_; + // for prefix seek mode to support prev() + Statistics* statistics_; + uint64_t max_skip_; + uint64_t max_skippable_internal_keys_; + uint64_t num_internal_keys_skipped_; + const Slice* iterate_lower_bound_; + const Slice* iterate_upper_bound_; + + IterKey prefix_start_buf_; + + Status status_; + Slice prefix_start_key_; + Direction direction_; + bool valid_; + bool current_entry_is_merged_; + const bool prefix_same_as_start_; + // Means that we will pin all data blocks we read as long the Iterator + // is not deleted, will be true if ReadOptions::pin_data is true + const bool pin_thru_lifetime_; + const bool total_order_seek_; + bool allow_blob_; + bool is_blob_; + bool arena_mode_; + // List of operands for merge operator. + MergeContext merge_context_; + ReadRangeDelAggregator range_del_agg_; + LocalStatistics local_stats_; + PinnedIteratorsManager pinned_iters_mgr_; + DBImpl* db_impl_; + ColumnFamilyData* cfd_; + // for diff snapshots we want the lower bound on the seqnum; + // if this value > 0 iterator will return internal keys + SequenceNumber start_seqnum_; + + // No copying allowed + DBIter(const DBIter&); + void operator=(const DBIter&); +}; + +inline bool DBIter::ParseKey(ParsedInternalKey* ikey) { + if (!ParseInternalKey(iter_->key(), ikey)) { + status_ = Status::Corruption("corrupted internal key in DBIter"); + valid_ = false; + ROCKS_LOG_ERROR(logger_, "corrupted internal key in DBIter: %s", + iter_->key().ToString(true).c_str()); + return false; + } else { + return true; + } +} + +void DBIter::Next() { + assert(valid_); + assert(status_.ok()); + + PERF_CPU_TIMER_GUARD(iter_next_cpu_nanos, env_); + // Release temporarily pinned blocks from last operation + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + bool ok = true; + if (direction_ == kReverse) { + if (!ReverseToForward()) { + ok = false; + } + } else if (iter_->Valid() && !current_entry_is_merged_) { + // If the current value is not a merge, the iter position is the + // current key, which is already returned. We can safely issue a + // Next() without checking the current key. + // If the current key is a merge, very likely iter already points + // to the next internal position. + iter_->Next(); + PERF_COUNTER_ADD(internal_key_skipped_count, 1); + } + + if (statistics_ != nullptr) { + local_stats_.next_count_++; + } + if (ok && iter_->Valid()) { + FindNextUserEntry(true /* skipping the current user key */, + prefix_same_as_start_); + } else { + valid_ = false; + } + if (statistics_ != nullptr && valid_) { + local_stats_.next_found_count_++; + local_stats_.bytes_read_ += (key().size() + value().size()); + } +} + +// PRE: saved_key_ has the current user key if skipping +// POST: saved_key_ should have the next user key if valid_, +// if the current entry is a result of merge +// current_entry_is_merged_ => true +// saved_value_ => the merged value +// +// NOTE: In between, saved_key_ can point to a user key that has +// a delete marker or a sequence number higher than sequence_ +// saved_key_ MUST have a proper user_key before calling this function +// +// The prefix_check parameter controls whether we check the iterated +// keys against the prefix of the seeked key. Set to false when +// performing a seek without a key (e.g. SeekToFirst). Set to +// prefix_same_as_start_ for other iterations. +inline bool DBIter::FindNextUserEntry(bool skipping, bool prefix_check) { + PERF_TIMER_GUARD(find_next_user_entry_time); + return FindNextUserEntryInternal(skipping, prefix_check); +} + +// Actual implementation of DBIter::FindNextUserEntry() +bool DBIter::FindNextUserEntryInternal(bool skipping, bool prefix_check) { + // Loop until we hit an acceptable entry to yield + assert(iter_->Valid()); + assert(status_.ok()); + assert(direction_ == kForward); + current_entry_is_merged_ = false; + + // How many times in a row we have skipped an entry with user key less than + // or equal to saved_key_. We could skip these entries either because + // sequence numbers were too high or because skipping = true. + // What saved_key_ contains throughout this method: + // - if skipping : saved_key_ contains the key that we need to skip, + // and we haven't seen any keys greater than that, + // - if num_skipped > 0 : saved_key_ contains the key that we have skipped + // num_skipped times, and we haven't seen any keys + // greater than that, + // - none of the above : saved_key_ can contain anything, it doesn't matter. + uint64_t num_skipped = 0; + + is_blob_ = false; + + do { + if (!ParseKey(&ikey_)) { + return false; + } + + if (iterate_upper_bound_ != nullptr && + user_comparator_.Compare(ikey_.user_key, *iterate_upper_bound_) >= 0) { + break; + } + + if (prefix_extractor_ && prefix_check && + prefix_extractor_->Transform(ikey_.user_key) + .compare(prefix_start_key_) != 0) { + break; + } + + if (TooManyInternalKeysSkipped()) { + return false; + } + + if (IsVisible(ikey_.sequence)) { + if (skipping && user_comparator_.Compare(ikey_.user_key, + saved_key_.GetUserKey()) <= 0) { + num_skipped++; // skip this entry + PERF_COUNTER_ADD(internal_key_skipped_count, 1); + } else { + num_skipped = 0; + switch (ikey_.type) { + case kTypeDeletion: + case kTypeSingleDeletion: + // Arrange to skip all upcoming entries for this key since + // they are hidden by this deletion. + // if iterartor specified start_seqnum we + // 1) return internal key, including the type + // 2) return ikey only if ikey.seqnum >= start_seqnum_ + // note that if deletion seqnum is < start_seqnum_ we + // just skip it like in normal iterator. + if (start_seqnum_ > 0 && ikey_.sequence >= start_seqnum_) { + saved_key_.SetInternalKey(ikey_); + valid_ = true; + return true; + } else { + saved_key_.SetUserKey( + ikey_.user_key, + !pin_thru_lifetime_ || !iter_->IsKeyPinned() /* copy */); + skipping = true; + PERF_COUNTER_ADD(internal_delete_skipped_count, 1); + } + break; + case kTypeValue: + case kTypeBlobIndex: + if (start_seqnum_ > 0) { + // we are taking incremental snapshot here + // incremental snapshots aren't supported on DB with range deletes + assert(!( + (ikey_.type == kTypeBlobIndex) && (start_seqnum_ > 0) + )); + if (ikey_.sequence >= start_seqnum_) { + saved_key_.SetInternalKey(ikey_); + valid_ = true; + return true; + } else { + // this key and all previous versions shouldn't be included, + // skipping + saved_key_.SetUserKey(ikey_.user_key, + !pin_thru_lifetime_ || !iter_->IsKeyPinned() /* copy */); + skipping = true; + } + } else { + saved_key_.SetUserKey( + ikey_.user_key, + !pin_thru_lifetime_ || !iter_->IsKeyPinned() /* copy */); + if (range_del_agg_.ShouldDelete( + ikey_, RangeDelPositioningMode::kForwardTraversal)) { + // Arrange to skip all upcoming entries for this key since + // they are hidden by this deletion. + skipping = true; + num_skipped = 0; + PERF_COUNTER_ADD(internal_delete_skipped_count, 1); + } else if (ikey_.type == kTypeBlobIndex) { + if (!allow_blob_) { + ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index."); + status_ = Status::NotSupported( + "Encounter unexpected blob index. Please open DB with " + "rocksdb::blob_db::BlobDB instead."); + valid_ = false; + return false; + } + + is_blob_ = true; + valid_ = true; + return true; + } else { + valid_ = true; + return true; + } + } + break; + case kTypeMerge: + saved_key_.SetUserKey( + ikey_.user_key, + !pin_thru_lifetime_ || !iter_->IsKeyPinned() /* copy */); + if (range_del_agg_.ShouldDelete( + ikey_, RangeDelPositioningMode::kForwardTraversal)) { + // Arrange to skip all upcoming entries for this key since + // they are hidden by this deletion. + skipping = true; + num_skipped = 0; + PERF_COUNTER_ADD(internal_delete_skipped_count, 1); + } else { + // By now, we are sure the current ikey is going to yield a + // value + current_entry_is_merged_ = true; + valid_ = true; + return MergeValuesNewToOld(); // Go to a different state machine + } + break; + default: + assert(false); + break; + } + } + } else { + PERF_COUNTER_ADD(internal_recent_skipped_count, 1); + + // This key was inserted after our snapshot was taken. + // If this happens too many times in a row for the same user key, we want + // to seek to the target sequence number. + int cmp = + user_comparator_.Compare(ikey_.user_key, saved_key_.GetUserKey()); + if (cmp == 0 || (skipping && cmp <= 0)) { + num_skipped++; + } else { + saved_key_.SetUserKey( + ikey_.user_key, + !iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */); + skipping = false; + num_skipped = 0; + } + } + + // If we have sequentially iterated via numerous equal keys, then it's + // better to seek so that we can avoid too many key comparisons. + if (num_skipped > max_skip_ && CanReseekToSkip()) { + num_skipped = 0; + std::string last_key; + if (skipping) { + // We're looking for the next user-key but all we see are the same + // user-key with decreasing sequence numbers. Fast forward to + // sequence number 0 and type deletion (the smallest type). + AppendInternalKey(&last_key, ParsedInternalKey(saved_key_.GetUserKey(), + 0, kTypeDeletion)); + // Don't set skipping = false because we may still see more user-keys + // equal to saved_key_. + } else { + // We saw multiple entries with this user key and sequence numbers + // higher than sequence_. Fast forward to sequence_. + // Note that this only covers a case when a higher key was overwritten + // many times since our snapshot was taken, not the case when a lot of + // different keys were inserted after our snapshot was taken. + AppendInternalKey(&last_key, + ParsedInternalKey(saved_key_.GetUserKey(), sequence_, + kValueTypeForSeek)); + } + iter_->Seek(last_key); + RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION); + } else { + iter_->Next(); + } + } while (iter_->Valid()); + + valid_ = false; + return iter_->status().ok(); +} + +// Merge values of the same user key starting from the current iter_ position +// Scan from the newer entries to older entries. +// PRE: iter_->key() points to the first merge type entry +// saved_key_ stores the user key +// POST: saved_value_ has the merged value for the user key +// iter_ points to the next entry (or invalid) +bool DBIter::MergeValuesNewToOld() { + if (!merge_operator_) { + ROCKS_LOG_ERROR(logger_, "Options::merge_operator is null."); + status_ = Status::InvalidArgument("merge_operator_ must be set."); + valid_ = false; + return false; + } + + // Temporarily pin the blocks that hold merge operands + TempPinData(); + merge_context_.Clear(); + // Start the merge process by pushing the first operand + merge_context_.PushOperand(iter_->value(), + iter_->IsValuePinned() /* operand_pinned */); + TEST_SYNC_POINT("DBIter::MergeValuesNewToOld:PushedFirstOperand"); + + ParsedInternalKey ikey; + Status s; + for (iter_->Next(); iter_->Valid(); iter_->Next()) { + TEST_SYNC_POINT("DBIter::MergeValuesNewToOld:SteppedToNextOperand"); + if (!ParseKey(&ikey)) { + return false; + } + + if (!user_comparator_.Equal(ikey.user_key, saved_key_.GetUserKey())) { + // hit the next user key, stop right here + break; + } else if (kTypeDeletion == ikey.type || kTypeSingleDeletion == ikey.type || + range_del_agg_.ShouldDelete( + ikey, RangeDelPositioningMode::kForwardTraversal)) { + // hit a delete with the same user key, stop right here + // iter_ is positioned after delete + iter_->Next(); + break; + } else if (kTypeValue == ikey.type) { + // hit a put, merge the put value with operands and store the + // final result in saved_value_. We are done! + const Slice val = iter_->value(); + s = MergeHelper::TimedFullMerge( + merge_operator_, ikey.user_key, &val, merge_context_.GetOperands(), + &saved_value_, logger_, statistics_, env_, &pinned_value_, true); + if (!s.ok()) { + valid_ = false; + status_ = s; + return false; + } + // iter_ is positioned after put + iter_->Next(); + if (!iter_->status().ok()) { + valid_ = false; + return false; + } + return true; + } else if (kTypeMerge == ikey.type) { + // hit a merge, add the value as an operand and run associative merge. + // when complete, add result to operands and continue. + merge_context_.PushOperand(iter_->value(), + iter_->IsValuePinned() /* operand_pinned */); + PERF_COUNTER_ADD(internal_merge_count, 1); + } else if (kTypeBlobIndex == ikey.type) { + if (!allow_blob_) { + ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index."); + status_ = Status::NotSupported( + "Encounter unexpected blob index. Please open DB with " + "rocksdb::blob_db::BlobDB instead."); + } else { + status_ = + Status::NotSupported("Blob DB does not support merge operator."); + } + valid_ = false; + return false; + } else { + assert(false); + } + } + + if (!iter_->status().ok()) { + valid_ = false; + return false; + } + + // we either exhausted all internal keys under this user key, or hit + // a deletion marker. + // feed null as the existing value to the merge operator, such that + // client can differentiate this scenario and do things accordingly. + s = MergeHelper::TimedFullMerge(merge_operator_, saved_key_.GetUserKey(), + nullptr, merge_context_.GetOperands(), + &saved_value_, logger_, statistics_, env_, + &pinned_value_, true); + if (!s.ok()) { + valid_ = false; + status_ = s; + return false; + } + + assert(status_.ok()); + return true; +} + +void DBIter::Prev() { + assert(valid_); + assert(status_.ok()); + + PERF_CPU_TIMER_GUARD(iter_prev_cpu_nanos, env_); + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + bool ok = true; + if (direction_ == kForward) { + if (!ReverseToBackward()) { + ok = false; + } + } + if (ok) { + PrevInternal(); + } + if (statistics_ != nullptr) { + local_stats_.prev_count_++; + if (valid_) { + local_stats_.prev_found_count_++; + local_stats_.bytes_read_ += (key().size() + value().size()); + } + } +} + +bool DBIter::ReverseToForward() { + assert(iter_->status().ok()); + + // When moving backwards, iter_ is positioned on _previous_ key, which may + // not exist or may have different prefix than the current key(). + // If that's the case, seek iter_ to current key. + if ((prefix_extractor_ != nullptr && !total_order_seek_) || !iter_->Valid()) { + IterKey last_key; + last_key.SetInternalKey(ParsedInternalKey( + saved_key_.GetUserKey(), kMaxSequenceNumber, kValueTypeForSeek)); + iter_->Seek(last_key.GetInternalKey()); + } + + direction_ = kForward; + // Skip keys less than the current key() (a.k.a. saved_key_). + while (iter_->Valid()) { + ParsedInternalKey ikey; + if (!ParseKey(&ikey)) { + return false; + } + if (user_comparator_.Compare(ikey.user_key, saved_key_.GetUserKey()) >= 0) { + return true; + } + iter_->Next(); + } + + if (!iter_->status().ok()) { + valid_ = false; + return false; + } + + return true; +} + +// Move iter_ to the key before saved_key_. +bool DBIter::ReverseToBackward() { + assert(iter_->status().ok()); + + // When current_entry_is_merged_ is true, iter_ may be positioned on the next + // key, which may not exist or may have prefix different from current. + // If that's the case, seek to saved_key_. + if (current_entry_is_merged_ && + ((prefix_extractor_ != nullptr && !total_order_seek_) || + !iter_->Valid())) { + IterKey last_key; + // Using kMaxSequenceNumber and kValueTypeForSeek + // (not kValueTypeForSeekForPrev) to seek to a key strictly smaller + // than saved_key_. + last_key.SetInternalKey(ParsedInternalKey( + saved_key_.GetUserKey(), kMaxSequenceNumber, kValueTypeForSeek)); + if (prefix_extractor_ != nullptr && !total_order_seek_) { + iter_->SeekForPrev(last_key.GetInternalKey()); + } else { + // Some iterators may not support SeekForPrev(), so we avoid using it + // when prefix seek mode is disabled. This is somewhat expensive + // (an extra Prev(), as well as an extra change of direction of iter_), + // so we may need to reconsider it later. + iter_->Seek(last_key.GetInternalKey()); + if (!iter_->Valid() && iter_->status().ok()) { + iter_->SeekToLast(); + } + } + } + + direction_ = kReverse; + return FindUserKeyBeforeSavedKey(); +} + +void DBIter::PrevInternal() { + while (iter_->Valid()) { + saved_key_.SetUserKey( + ExtractUserKey(iter_->key()), + !iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */); + + if (prefix_extractor_ && prefix_same_as_start_ && + prefix_extractor_->Transform(saved_key_.GetUserKey()) + .compare(prefix_start_key_) != 0) { + // Current key does not have the same prefix as start + valid_ = false; + return; + } + + if (iterate_lower_bound_ != nullptr && + user_comparator_.Compare(saved_key_.GetUserKey(), + *iterate_lower_bound_) < 0) { + // We've iterated earlier than the user-specified lower bound. + valid_ = false; + return; + } + + if (!FindValueForCurrentKey()) { // assigns valid_ + return; + } + + // Whether or not we found a value for current key, we need iter_ to end up + // on a smaller key. + if (!FindUserKeyBeforeSavedKey()) { + return; + } + + if (valid_) { + // Found the value. + return; + } + + if (TooManyInternalKeysSkipped(false)) { + return; + } + } + + // We haven't found any key - iterator is not valid + valid_ = false; +} + +// Used for backwards iteration. +// Looks at the entries with user key saved_key_ and finds the most up-to-date +// value for it, or executes a merge, or determines that the value was deleted. +// Sets valid_ to true if the value is found and is ready to be presented to +// the user through value(). +// Sets valid_ to false if the value was deleted, and we should try another key. +// Returns false if an error occurred, and !status().ok() and !valid_. +// +// PRE: iter_ is positioned on the last entry with user key equal to saved_key_. +// POST: iter_ is positioned on one of the entries equal to saved_key_, or on +// the entry just before them, or on the entry just after them. +bool DBIter::FindValueForCurrentKey() { + assert(iter_->Valid()); + merge_context_.Clear(); + current_entry_is_merged_ = false; + // last entry before merge (could be kTypeDeletion, kTypeSingleDeletion or + // kTypeValue) + ValueType last_not_merge_type = kTypeDeletion; + ValueType last_key_entry_type = kTypeDeletion; + + // Temporarily pin blocks that hold (merge operands / the value) + ReleaseTempPinnedData(); + TempPinData(); + size_t num_skipped = 0; + while (iter_->Valid()) { + ParsedInternalKey ikey; + if (!ParseKey(&ikey)) { + return false; + } + + if (!IsVisible(ikey.sequence) || + !user_comparator_.Equal(ikey.user_key, saved_key_.GetUserKey())) { + break; + } + if (TooManyInternalKeysSkipped()) { + return false; + } + + // This user key has lots of entries. + // We're going from old to new, and it's taking too long. Let's do a Seek() + // and go from new to old. This helps when a key was overwritten many times. + if (num_skipped >= max_skip_ && CanReseekToSkip()) { + return FindValueForCurrentKeyUsingSeek(); + } + + last_key_entry_type = ikey.type; + switch (last_key_entry_type) { + case kTypeValue: + case kTypeBlobIndex: + if (range_del_agg_.ShouldDelete( + ikey, RangeDelPositioningMode::kBackwardTraversal)) { + last_key_entry_type = kTypeRangeDeletion; + PERF_COUNTER_ADD(internal_delete_skipped_count, 1); + } else { + assert(iter_->IsValuePinned()); + pinned_value_ = iter_->value(); + } + merge_context_.Clear(); + last_not_merge_type = last_key_entry_type; + break; + case kTypeDeletion: + case kTypeSingleDeletion: + merge_context_.Clear(); + last_not_merge_type = last_key_entry_type; + PERF_COUNTER_ADD(internal_delete_skipped_count, 1); + break; + case kTypeMerge: + if (range_del_agg_.ShouldDelete( + ikey, RangeDelPositioningMode::kBackwardTraversal)) { + merge_context_.Clear(); + last_key_entry_type = kTypeRangeDeletion; + last_not_merge_type = last_key_entry_type; + PERF_COUNTER_ADD(internal_delete_skipped_count, 1); + } else { + assert(merge_operator_ != nullptr); + merge_context_.PushOperandBack( + iter_->value(), iter_->IsValuePinned() /* operand_pinned */); + PERF_COUNTER_ADD(internal_merge_count, 1); + } + break; + default: + assert(false); + } + + PERF_COUNTER_ADD(internal_key_skipped_count, 1); + iter_->Prev(); + ++num_skipped; + } + + if (!iter_->status().ok()) { + valid_ = false; + return false; + } + + Status s; + is_blob_ = false; + switch (last_key_entry_type) { + case kTypeDeletion: + case kTypeSingleDeletion: + case kTypeRangeDeletion: + valid_ = false; + return true; + case kTypeMerge: + current_entry_is_merged_ = true; + if (last_not_merge_type == kTypeDeletion || + last_not_merge_type == kTypeSingleDeletion || + last_not_merge_type == kTypeRangeDeletion) { + s = MergeHelper::TimedFullMerge( + merge_operator_, saved_key_.GetUserKey(), nullptr, + merge_context_.GetOperands(), &saved_value_, logger_, statistics_, + env_, &pinned_value_, true); + } else if (last_not_merge_type == kTypeBlobIndex) { + if (!allow_blob_) { + ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index."); + status_ = Status::NotSupported( + "Encounter unexpected blob index. Please open DB with " + "rocksdb::blob_db::BlobDB instead."); + } else { + status_ = + Status::NotSupported("Blob DB does not support merge operator."); + } + valid_ = false; + return false; + } else { + assert(last_not_merge_type == kTypeValue); + s = MergeHelper::TimedFullMerge( + merge_operator_, saved_key_.GetUserKey(), &pinned_value_, + merge_context_.GetOperands(), &saved_value_, logger_, statistics_, + env_, &pinned_value_, true); + } + break; + case kTypeValue: + // do nothing - we've already has value in pinned_value_ + break; + case kTypeBlobIndex: + if (!allow_blob_) { + ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index."); + status_ = Status::NotSupported( + "Encounter unexpected blob index. Please open DB with " + "rocksdb::blob_db::BlobDB instead."); + valid_ = false; + return false; + } + is_blob_ = true; + break; + default: + assert(false); + break; + } + if (!s.ok()) { + valid_ = false; + status_ = s; + return false; + } + valid_ = true; + return true; +} + +// This function is used in FindValueForCurrentKey. +// We use Seek() function instead of Prev() to find necessary value +// TODO: This is very similar to FindNextUserEntry() and MergeValuesNewToOld(). +// Would be nice to reuse some code. +bool DBIter::FindValueForCurrentKeyUsingSeek() { + // FindValueForCurrentKey will enable pinning before calling + // FindValueForCurrentKeyUsingSeek() + assert(pinned_iters_mgr_.PinningEnabled()); + std::string last_key; + AppendInternalKey(&last_key, ParsedInternalKey(saved_key_.GetUserKey(), + sequence_, kValueTypeForSeek)); + iter_->Seek(last_key); + RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION); + + // In case read_callback presents, the value we seek to may not be visible. + // Find the next value that's visible. + ParsedInternalKey ikey; + while (true) { + if (!iter_->Valid()) { + valid_ = false; + return iter_->status().ok(); + } + + if (!ParseKey(&ikey)) { + return false; + } + if (!user_comparator_.Equal(ikey.user_key, saved_key_.GetUserKey())) { + // No visible values for this key, even though FindValueForCurrentKey() + // has seen some. This is possible if we're using a tailing iterator, and + // the entries were discarded in a compaction. + valid_ = false; + return true; + } + + if (IsVisible(ikey.sequence)) { + break; + } + + iter_->Next(); + } + + if (ikey.type == kTypeDeletion || ikey.type == kTypeSingleDeletion || + range_del_agg_.ShouldDelete( + ikey, RangeDelPositioningMode::kBackwardTraversal)) { + valid_ = false; + return true; + } + if (ikey.type == kTypeBlobIndex && !allow_blob_) { + ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index."); + status_ = Status::NotSupported( + "Encounter unexpected blob index. Please open DB with " + "rocksdb::blob_db::BlobDB instead."); + valid_ = false; + return false; + } + if (ikey.type == kTypeValue || ikey.type == kTypeBlobIndex) { + assert(iter_->IsValuePinned()); + pinned_value_ = iter_->value(); + valid_ = true; + return true; + } + + // kTypeMerge. We need to collect all kTypeMerge values and save them + // in operands + assert(ikey.type == kTypeMerge); + current_entry_is_merged_ = true; + merge_context_.Clear(); + merge_context_.PushOperand(iter_->value(), + iter_->IsValuePinned() /* operand_pinned */); + while (true) { + iter_->Next(); + + if (!iter_->Valid()) { + if (!iter_->status().ok()) { + valid_ = false; + return false; + } + break; + } + if (!ParseKey(&ikey)) { + return false; + } + if (!user_comparator_.Equal(ikey.user_key, saved_key_.GetUserKey())) { + break; + } + + if (ikey.type == kTypeDeletion || ikey.type == kTypeSingleDeletion || + range_del_agg_.ShouldDelete( + ikey, RangeDelPositioningMode::kForwardTraversal)) { + break; + } else if (ikey.type == kTypeValue) { + const Slice val = iter_->value(); + Status s = MergeHelper::TimedFullMerge( + merge_operator_, saved_key_.GetUserKey(), &val, + merge_context_.GetOperands(), &saved_value_, logger_, statistics_, + env_, &pinned_value_, true); + if (!s.ok()) { + valid_ = false; + status_ = s; + return false; + } + valid_ = true; + return true; + } else if (ikey.type == kTypeMerge) { + merge_context_.PushOperand(iter_->value(), + iter_->IsValuePinned() /* operand_pinned */); + PERF_COUNTER_ADD(internal_merge_count, 1); + } else if (ikey.type == kTypeBlobIndex) { + if (!allow_blob_) { + ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index."); + status_ = Status::NotSupported( + "Encounter unexpected blob index. Please open DB with " + "rocksdb::blob_db::BlobDB instead."); + } else { + status_ = + Status::NotSupported("Blob DB does not support merge operator."); + } + valid_ = false; + return false; + } else { + assert(false); + } + } + + Status s = MergeHelper::TimedFullMerge( + merge_operator_, saved_key_.GetUserKey(), nullptr, + merge_context_.GetOperands(), &saved_value_, logger_, statistics_, env_, + &pinned_value_, true); + if (!s.ok()) { + valid_ = false; + status_ = s; + return false; + } + + // Make sure we leave iter_ in a good state. If it's valid and we don't care + // about prefixes, that's already good enough. Otherwise it needs to be + // seeked to the current key. + if ((prefix_extractor_ != nullptr && !total_order_seek_) || !iter_->Valid()) { + if (prefix_extractor_ != nullptr && !total_order_seek_) { + iter_->SeekForPrev(last_key); + } else { + iter_->Seek(last_key); + if (!iter_->Valid() && iter_->status().ok()) { + iter_->SeekToLast(); + } + } + RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION); + } + + valid_ = true; + return true; +} + +// Move backwards until the key smaller than saved_key_. +// Changes valid_ only if return value is false. +bool DBIter::FindUserKeyBeforeSavedKey() { + assert(status_.ok()); + size_t num_skipped = 0; + while (iter_->Valid()) { + ParsedInternalKey ikey; + if (!ParseKey(&ikey)) { + return false; + } + + if (user_comparator_.Compare(ikey.user_key, saved_key_.GetUserKey()) < 0) { + return true; + } + + if (TooManyInternalKeysSkipped()) { + return false; + } + + assert(ikey.sequence != kMaxSequenceNumber); + if (!IsVisible(ikey.sequence)) { + PERF_COUNTER_ADD(internal_recent_skipped_count, 1); + } else { + PERF_COUNTER_ADD(internal_key_skipped_count, 1); + } + + if (num_skipped >= max_skip_ && CanReseekToSkip()) { + num_skipped = 0; + IterKey last_key; + last_key.SetInternalKey(ParsedInternalKey( + saved_key_.GetUserKey(), kMaxSequenceNumber, kValueTypeForSeek)); + // It would be more efficient to use SeekForPrev() here, but some + // iterators may not support it. + iter_->Seek(last_key.GetInternalKey()); + RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION); + if (!iter_->Valid()) { + break; + } + } else { + ++num_skipped; + } + + iter_->Prev(); + } + + if (!iter_->status().ok()) { + valid_ = false; + return false; + } + + return true; +} + +bool DBIter::TooManyInternalKeysSkipped(bool increment) { + if ((max_skippable_internal_keys_ > 0) && + (num_internal_keys_skipped_ > max_skippable_internal_keys_)) { + valid_ = false; + status_ = Status::Incomplete("Too many internal keys skipped."); + return true; + } else if (increment) { + num_internal_keys_skipped_++; + } + return false; +} + +bool DBIter::IsVisible(SequenceNumber sequence) { + if (read_callback_ == nullptr) { + return sequence <= sequence_; + } else { + return read_callback_->IsVisible(sequence); + } +} + +bool DBIter::CanReseekToSkip() { + return read_callback_ == nullptr || read_callback_->CanReseekToSkip(); +} + +void DBIter::Seek(const Slice& target) { + PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, env_); + StopWatch sw(env_, statistics_, DB_SEEK); + status_ = Status::OK(); + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + + SequenceNumber seq = sequence_; + saved_key_.Clear(); + saved_key_.SetInternalKey(target, seq); + +#ifndef ROCKSDB_LITE + if (db_impl_ != nullptr && cfd_ != nullptr) { + db_impl_->TraceIteratorSeek(cfd_->GetID(), target); + } +#endif // ROCKSDB_LITE + + if (iterate_lower_bound_ != nullptr && + user_comparator_.Compare(saved_key_.GetUserKey(), *iterate_lower_bound_) < + 0) { + saved_key_.Clear(); + saved_key_.SetInternalKey(*iterate_lower_bound_, seq); + } + + { + PERF_TIMER_GUARD(seek_internal_seek_time); + iter_->Seek(saved_key_.GetInternalKey()); + range_del_agg_.InvalidateRangeDelMapPositions(); + } + RecordTick(statistics_, NUMBER_DB_SEEK); + if (iter_->Valid()) { + if (prefix_extractor_ && prefix_same_as_start_) { + prefix_start_key_ = prefix_extractor_->Transform(target); + } + direction_ = kForward; + ClearSavedValue(); + FindNextUserEntry(false /* not skipping */, prefix_same_as_start_); + if (!valid_) { + prefix_start_key_.clear(); + } + if (statistics_ != nullptr) { + if (valid_) { + // Decrement since we don't want to count this key as skipped + RecordTick(statistics_, NUMBER_DB_SEEK_FOUND); + RecordTick(statistics_, ITER_BYTES_READ, key().size() + value().size()); + PERF_COUNTER_ADD(iter_read_bytes, key().size() + value().size()); + } + } + } else { + valid_ = false; + } + + if (valid_ && prefix_extractor_ && prefix_same_as_start_) { + prefix_start_buf_.SetUserKey(prefix_start_key_); + prefix_start_key_ = prefix_start_buf_.GetUserKey(); + } +} + +void DBIter::SeekForPrev(const Slice& target) { + PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, env_); + StopWatch sw(env_, statistics_, DB_SEEK); + status_ = Status::OK(); + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + saved_key_.Clear(); + // now saved_key is used to store internal key. + saved_key_.SetInternalKey(target, 0 /* sequence_number */, + kValueTypeForSeekForPrev); + + if (iterate_upper_bound_ != nullptr && + user_comparator_.Compare(saved_key_.GetUserKey(), + *iterate_upper_bound_) >= 0) { + saved_key_.Clear(); + saved_key_.SetInternalKey(*iterate_upper_bound_, kMaxSequenceNumber); + } + + { + PERF_TIMER_GUARD(seek_internal_seek_time); + iter_->SeekForPrev(saved_key_.GetInternalKey()); + range_del_agg_.InvalidateRangeDelMapPositions(); + } + +#ifndef ROCKSDB_LITE + if (db_impl_ != nullptr && cfd_ != nullptr) { + db_impl_->TraceIteratorSeekForPrev(cfd_->GetID(), target); + } +#endif // ROCKSDB_LITE + + RecordTick(statistics_, NUMBER_DB_SEEK); + if (iter_->Valid()) { + if (prefix_extractor_ && prefix_same_as_start_) { + prefix_start_key_ = prefix_extractor_->Transform(target); + } + direction_ = kReverse; + ClearSavedValue(); + PrevInternal(); + if (!valid_) { + prefix_start_key_.clear(); + } + if (statistics_ != nullptr) { + if (valid_) { + RecordTick(statistics_, NUMBER_DB_SEEK_FOUND); + RecordTick(statistics_, ITER_BYTES_READ, key().size() + value().size()); + PERF_COUNTER_ADD(iter_read_bytes, key().size() + value().size()); + } + } + } else { + valid_ = false; + } + if (valid_ && prefix_extractor_ && prefix_same_as_start_) { + prefix_start_buf_.SetUserKey(prefix_start_key_); + prefix_start_key_ = prefix_start_buf_.GetUserKey(); + } +} + +void DBIter::SeekToFirst() { + if (iterate_lower_bound_ != nullptr) { + Seek(*iterate_lower_bound_); + return; + } + PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, env_); + // Don't use iter_::Seek() if we set a prefix extractor + // because prefix seek will be used. + if (prefix_extractor_ != nullptr && !total_order_seek_) { + max_skip_ = std::numeric_limits<uint64_t>::max(); + } + status_ = Status::OK(); + direction_ = kForward; + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + ClearSavedValue(); + + { + PERF_TIMER_GUARD(seek_internal_seek_time); + iter_->SeekToFirst(); + range_del_agg_.InvalidateRangeDelMapPositions(); + } + + RecordTick(statistics_, NUMBER_DB_SEEK); + if (iter_->Valid()) { + saved_key_.SetUserKey( + ExtractUserKey(iter_->key()), + !iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */); + FindNextUserEntry(false /* not skipping */, false /* no prefix check */); + if (statistics_ != nullptr) { + if (valid_) { + RecordTick(statistics_, NUMBER_DB_SEEK_FOUND); + RecordTick(statistics_, ITER_BYTES_READ, key().size() + value().size()); + PERF_COUNTER_ADD(iter_read_bytes, key().size() + value().size()); + } + } + } else { + valid_ = false; + } + if (valid_ && prefix_extractor_ && prefix_same_as_start_) { + prefix_start_buf_.SetUserKey( + prefix_extractor_->Transform(saved_key_.GetUserKey())); + prefix_start_key_ = prefix_start_buf_.GetUserKey(); + } +} + +void DBIter::SeekToLast() { + if (iterate_upper_bound_ != nullptr) { + // Seek to last key strictly less than ReadOptions.iterate_upper_bound. + SeekForPrev(*iterate_upper_bound_); + if (Valid() && user_comparator_.Equal(*iterate_upper_bound_, key())) { + ReleaseTempPinnedData(); + PrevInternal(); + } + return; + } + + PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, env_); + // Don't use iter_::Seek() if we set a prefix extractor + // because prefix seek will be used. + if (prefix_extractor_ != nullptr && !total_order_seek_) { + max_skip_ = std::numeric_limits<uint64_t>::max(); + } + status_ = Status::OK(); + direction_ = kReverse; + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + ClearSavedValue(); + + { + PERF_TIMER_GUARD(seek_internal_seek_time); + iter_->SeekToLast(); + range_del_agg_.InvalidateRangeDelMapPositions(); + } + PrevInternal(); + if (statistics_ != nullptr) { + RecordTick(statistics_, NUMBER_DB_SEEK); + if (valid_) { + RecordTick(statistics_, NUMBER_DB_SEEK_FOUND); + RecordTick(statistics_, ITER_BYTES_READ, key().size() + value().size()); + PERF_COUNTER_ADD(iter_read_bytes, key().size() + value().size()); + } + } + if (valid_ && prefix_extractor_ && prefix_same_as_start_) { + prefix_start_buf_.SetUserKey( + prefix_extractor_->Transform(saved_key_.GetUserKey())); + prefix_start_key_ = prefix_start_buf_.GetUserKey(); + } +} + +Iterator* NewDBIterator(Env* env, const ReadOptions& read_options, + const ImmutableCFOptions& cf_options, + const MutableCFOptions& mutable_cf_options, + const Comparator* user_key_comparator, + InternalIterator* internal_iter, + const SequenceNumber& sequence, + uint64_t max_sequential_skip_in_iterations, + ReadCallback* read_callback, DBImpl* db_impl, + ColumnFamilyData* cfd, bool allow_blob) { + DBIter* db_iter = new DBIter( + env, read_options, cf_options, mutable_cf_options, user_key_comparator, + internal_iter, sequence, false, max_sequential_skip_in_iterations, + read_callback, db_impl, cfd, allow_blob); + return db_iter; +} + +ArenaWrappedDBIter::~ArenaWrappedDBIter() { db_iter_->~DBIter(); } + +ReadRangeDelAggregator* ArenaWrappedDBIter::GetRangeDelAggregator() { + return db_iter_->GetRangeDelAggregator(); +} + +void ArenaWrappedDBIter::SetIterUnderDBIter(InternalIterator* iter) { + static_cast<DBIter*>(db_iter_)->SetIter(iter); +} + +inline bool ArenaWrappedDBIter::Valid() const { return db_iter_->Valid(); } +inline void ArenaWrappedDBIter::SeekToFirst() { db_iter_->SeekToFirst(); } +inline void ArenaWrappedDBIter::SeekToLast() { db_iter_->SeekToLast(); } +inline void ArenaWrappedDBIter::Seek(const Slice& target) { + db_iter_->Seek(target); +} +inline void ArenaWrappedDBIter::SeekForPrev(const Slice& target) { + db_iter_->SeekForPrev(target); +} +inline void ArenaWrappedDBIter::Next() { db_iter_->Next(); } +inline void ArenaWrappedDBIter::Prev() { db_iter_->Prev(); } +inline Slice ArenaWrappedDBIter::key() const { return db_iter_->key(); } +inline Slice ArenaWrappedDBIter::value() const { return db_iter_->value(); } +inline Status ArenaWrappedDBIter::status() const { return db_iter_->status(); } +bool ArenaWrappedDBIter::IsBlob() const { return db_iter_->IsBlob(); } +inline Status ArenaWrappedDBIter::GetProperty(std::string prop_name, + std::string* prop) { + if (prop_name == "rocksdb.iterator.super-version-number") { + // First try to pass the value returned from inner iterator. + if (!db_iter_->GetProperty(prop_name, prop).ok()) { + *prop = ToString(sv_number_); + } + return Status::OK(); + } + return db_iter_->GetProperty(prop_name, prop); +} + +void ArenaWrappedDBIter::Init(Env* env, const ReadOptions& read_options, + const ImmutableCFOptions& cf_options, + const MutableCFOptions& mutable_cf_options, + const SequenceNumber& sequence, + uint64_t max_sequential_skip_in_iteration, + uint64_t version_number, + ReadCallback* read_callback, DBImpl* db_impl, + ColumnFamilyData* cfd, bool allow_blob, + bool allow_refresh) { + auto mem = arena_.AllocateAligned(sizeof(DBIter)); + db_iter_ = new (mem) DBIter(env, read_options, cf_options, mutable_cf_options, + cf_options.user_comparator, nullptr, sequence, + true, max_sequential_skip_in_iteration, + read_callback, db_impl, cfd, allow_blob); + sv_number_ = version_number; + allow_refresh_ = allow_refresh; +} + +Status ArenaWrappedDBIter::Refresh() { + if (cfd_ == nullptr || db_impl_ == nullptr || !allow_refresh_) { + return Status::NotSupported("Creating renew iterator is not allowed."); + } + assert(db_iter_ != nullptr); + // TODO(yiwu): For last_seq_same_as_publish_seq_==false, this is not the + // correct behavior. Will be corrected automatically when we take a snapshot + // here for the case of WritePreparedTxnDB. + SequenceNumber latest_seq = db_impl_->GetLatestSequenceNumber(); + uint64_t cur_sv_number = cfd_->GetSuperVersionNumber(); + if (sv_number_ != cur_sv_number) { + Env* env = db_iter_->env(); + db_iter_->~DBIter(); + arena_.~Arena(); + new (&arena_) Arena(); + + SuperVersion* sv = cfd_->GetReferencedSuperVersion(db_impl_->mutex()); + if (read_callback_) { + read_callback_->Refresh(latest_seq); + } + Init(env, read_options_, *(cfd_->ioptions()), sv->mutable_cf_options, + latest_seq, sv->mutable_cf_options.max_sequential_skip_in_iterations, + cur_sv_number, read_callback_, db_impl_, cfd_, allow_blob_, + allow_refresh_); + + InternalIterator* internal_iter = db_impl_->NewInternalIterator( + read_options_, cfd_, sv, &arena_, db_iter_->GetRangeDelAggregator(), + latest_seq); + SetIterUnderDBIter(internal_iter); + } else { + db_iter_->set_sequence(latest_seq); + db_iter_->set_valid(false); + } + return Status::OK(); +} + +ArenaWrappedDBIter* NewArenaWrappedDbIterator( + Env* env, const ReadOptions& read_options, + const ImmutableCFOptions& cf_options, + const MutableCFOptions& mutable_cf_options, const SequenceNumber& sequence, + uint64_t max_sequential_skip_in_iterations, uint64_t version_number, + ReadCallback* read_callback, DBImpl* db_impl, ColumnFamilyData* cfd, + bool allow_blob, bool allow_refresh) { + ArenaWrappedDBIter* iter = new ArenaWrappedDBIter(); + iter->Init(env, read_options, cf_options, mutable_cf_options, sequence, + max_sequential_skip_in_iterations, version_number, read_callback, + db_impl, cfd, allow_blob, allow_refresh); + if (db_impl != nullptr && cfd != nullptr && allow_refresh) { + iter->StoreRefreshInfo(read_options, db_impl, cfd, read_callback, + allow_blob); + } + + return iter; +} + +} // namespace rocksdb |