// 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 #include #include #include "db/dbformat.h" #include "db/merge_context.h" #include "db/merge_helper.h" #include "db/pinned_iterators_manager.h" #include "db/wide/wide_column_serialization.h" #include "file/filename.h" #include "logging/logging.h" #include "memory/arena.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 "rocksdb/system_clock.h" #include "table/internal_iterator.h" #include "table/iterator_wrapper.h" #include "trace_replay/trace_replay.h" #include "util/mutexlock.h" #include "util/string_util.h" #include "util/user_comparator_wrapper.h" namespace ROCKSDB_NAMESPACE { DBIter::DBIter(Env* _env, const ReadOptions& read_options, const ImmutableOptions& ioptions, const MutableCFOptions& mutable_cf_options, const Comparator* cmp, InternalIterator* iter, const Version* version, SequenceNumber s, bool arena_mode, uint64_t max_sequential_skip_in_iterations, ReadCallback* read_callback, DBImpl* db_impl, ColumnFamilyData* cfd, bool expose_blob_index) : prefix_extractor_(mutable_cf_options.prefix_extractor.get()), env_(_env), clock_(ioptions.clock), logger_(ioptions.logger), user_comparator_(cmp), merge_operator_(ioptions.merge_operator.get()), iter_(iter), version_(version), read_callback_(read_callback), sequence_(s), statistics_(ioptions.stats), max_skip_(max_sequential_skip_in_iterations), max_skippable_internal_keys_(read_options.max_skippable_internal_keys), 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), is_key_seqnum_zero_(false), prefix_same_as_start_(mutable_cf_options.prefix_extractor ? read_options.prefix_same_as_start : false), pin_thru_lifetime_(read_options.pin_data), expect_total_order_inner_iter_(prefix_extractor_ == nullptr || read_options.total_order_seek || read_options.auto_prefix_mode), read_tier_(read_options.read_tier), fill_cache_(read_options.fill_cache), verify_checksums_(read_options.verify_checksums), expose_blob_index_(expose_blob_index), is_blob_(false), arena_mode_(arena_mode), io_activity_(read_options.io_activity), db_impl_(db_impl), cfd_(cfd), timestamp_ub_(read_options.timestamp), timestamp_lb_(read_options.iter_start_ts), timestamp_size_(timestamp_ub_ ? timestamp_ub_->size() : 0) { RecordTick(statistics_, NO_ITERATOR_CREATED); if (pin_thru_lifetime_) { pinned_iters_mgr_.StartPinning(); } if (iter_.iter()) { iter_.iter()->SetPinnedItersMgr(&pinned_iters_mgr_); } status_.PermitUncheckedError(); assert(timestamp_size_ == user_comparator_.user_comparator()->timestamp_size()); } Status DBIter::GetProperty(std::string prop_name, std::string* prop) { 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_.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."); } bool DBIter::ParseKey(ParsedInternalKey* ikey) { Status s = ParseInternalKey(iter_.key(), ikey, false /* log_err_key */); if (!s.ok()) { status_ = Status::Corruption("In DBIter: ", s.getState()); valid_ = false; ROCKS_LOG_ERROR(logger_, "In DBIter: %s", status_.getState()); return false; } else { return true; } } void DBIter::Next() { assert(valid_); assert(status_.ok()); PERF_COUNTER_ADD(iter_next_count, 1); PERF_CPU_TIMER_GUARD(iter_next_cpu_nanos, clock_); // Release temporarily pinned blocks from last operation ReleaseTempPinnedData(); ResetBlobValue(); ResetValueAndColumns(); local_stats_.skip_count_ += num_internal_keys_skipped_; local_stats_.skip_count_--; num_internal_keys_skipped_ = 0; bool ok = true; if (direction_ == kReverse) { is_key_seqnum_zero_ = false; if (!ReverseToForward()) { ok = false; } } else if (!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. assert(iter_.Valid()); iter_.Next(); PERF_COUNTER_ADD(internal_key_skipped_count, 1); } local_stats_.next_count_++; if (ok && iter_.Valid()) { ClearSavedValue(); if (prefix_same_as_start_) { assert(prefix_extractor_ != nullptr); const Slice prefix = prefix_.GetUserKey(); FindNextUserEntry(true /* skipping the current user key */, &prefix); } else { FindNextUserEntry(true /* skipping the current user key */, nullptr); } } else { is_key_seqnum_zero_ = false; valid_ = false; } if (statistics_ != nullptr && valid_) { local_stats_.next_found_count_++; local_stats_.bytes_read_ += (key().size() + value().size()); } } bool DBIter::SetBlobValueIfNeeded(const Slice& user_key, const Slice& blob_index) { assert(!is_blob_); assert(blob_value_.empty()); if (expose_blob_index_) { // Stacked BlobDB implementation is_blob_ = true; return true; } if (!version_) { status_ = Status::Corruption("Encountered unexpected blob index."); valid_ = false; return false; } // TODO: consider moving ReadOptions from ArenaWrappedDBIter to DBIter to // avoid having to copy options back and forth. ReadOptions read_options; read_options.read_tier = read_tier_; read_options.fill_cache = fill_cache_; read_options.verify_checksums = verify_checksums_; read_options.io_activity = io_activity_; constexpr FilePrefetchBuffer* prefetch_buffer = nullptr; constexpr uint64_t* bytes_read = nullptr; const Status s = version_->GetBlob(read_options, user_key, blob_index, prefetch_buffer, &blob_value_, bytes_read); if (!s.ok()) { status_ = s; valid_ = false; return false; } is_blob_ = true; return true; } bool DBIter::SetValueAndColumnsFromEntity(Slice slice) { assert(value_.empty()); assert(wide_columns_.empty()); const Status s = WideColumnSerialization::Deserialize(slice, wide_columns_); if (!s.ok()) { status_ = s; valid_ = false; return false; } if (!wide_columns_.empty() && wide_columns_[0].name() == kDefaultWideColumnName) { value_ = wide_columns_[0].value(); } return true; } // PRE: saved_key_ has the current user key if skipping_saved_key // 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 parameter, if not null, indicates that we need to iterate // within the prefix, and the iterator needs to be made invalid, if no // more entry for the prefix can be found. bool DBIter::FindNextUserEntry(bool skipping_saved_key, const Slice* prefix) { PERF_TIMER_GUARD(find_next_user_entry_time); return FindNextUserEntryInternal(skipping_saved_key, prefix); } // Actual implementation of DBIter::FindNextUserEntry() bool DBIter::FindNextUserEntryInternal(bool skipping_saved_key, const Slice* prefix) { // 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_saved_key = true. // What saved_key_ contains throughout this method: // - if skipping_saved_key : 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; // For write unprepared, the target sequence number in reseek could be larger // than the snapshot, and thus needs to be skipped again. This could result in // an infinite loop of reseeks. To avoid that, we limit the number of reseeks // to one. bool reseek_done = false; do { // Will update is_key_seqnum_zero_ as soon as we parsed the current key // but we need to save the previous value to be used in the loop. bool is_prev_key_seqnum_zero = is_key_seqnum_zero_; if (!ParseKey(&ikey_)) { is_key_seqnum_zero_ = false; return false; } Slice user_key_without_ts = StripTimestampFromUserKey(ikey_.user_key, timestamp_size_); is_key_seqnum_zero_ = (ikey_.sequence == 0); assert(iterate_upper_bound_ == nullptr || iter_.UpperBoundCheckResult() != IterBoundCheck::kInbound || user_comparator_.CompareWithoutTimestamp( user_key_without_ts, /*a_has_ts=*/false, *iterate_upper_bound_, /*b_has_ts=*/false) < 0); if (iterate_upper_bound_ != nullptr && iter_.UpperBoundCheckResult() != IterBoundCheck::kInbound && user_comparator_.CompareWithoutTimestamp( user_key_without_ts, /*a_has_ts=*/false, *iterate_upper_bound_, /*b_has_ts=*/false) >= 0) { break; } assert(prefix == nullptr || prefix_extractor_ != nullptr); if (prefix != nullptr && prefix_extractor_->Transform(user_key_without_ts).compare(*prefix) != 0) { assert(prefix_same_as_start_); break; } if (TooManyInternalKeysSkipped()) { return false; } assert(ikey_.user_key.size() >= timestamp_size_); Slice ts = timestamp_size_ > 0 ? ExtractTimestampFromUserKey( ikey_.user_key, timestamp_size_) : Slice(); bool more_recent = false; if (IsVisible(ikey_.sequence, ts, &more_recent)) { // If the previous entry is of seqnum 0, the current entry will not // possibly be skipped. This condition can potentially be relaxed to // prev_key.seq <= ikey_.sequence. We are cautious because it will be more // prone to bugs causing the same user key with the same sequence number. // Note that with current timestamp implementation, the same user key can // have different timestamps and zero sequence number on the bottommost // level. This may change in the future. if ((!is_prev_key_seqnum_zero || timestamp_size_ > 0) && skipping_saved_key && CompareKeyForSkip(ikey_.user_key, saved_key_.GetUserKey()) <= 0) { num_skipped++; // skip this entry PERF_COUNTER_ADD(internal_key_skipped_count, 1); } else { assert(!skipping_saved_key || CompareKeyForSkip(ikey_.user_key, saved_key_.GetUserKey()) > 0); num_skipped = 0; reseek_done = false; switch (ikey_.type) { case kTypeDeletion: case kTypeDeletionWithTimestamp: case kTypeSingleDeletion: // Arrange to skip all upcoming entries for this key since // they are hidden by this deletion. if (timestamp_lb_) { saved_key_.SetInternalKey(ikey_); valid_ = true; return true; } else { saved_key_.SetUserKey( ikey_.user_key, !pin_thru_lifetime_ || !iter_.iter()->IsKeyPinned() /* copy */); skipping_saved_key = true; PERF_COUNTER_ADD(internal_delete_skipped_count, 1); } break; case kTypeValue: case kTypeBlobIndex: case kTypeWideColumnEntity: if (!iter_.PrepareValue()) { assert(!iter_.status().ok()); valid_ = false; return false; } if (timestamp_lb_) { saved_key_.SetInternalKey(ikey_); } else { saved_key_.SetUserKey( ikey_.user_key, !pin_thru_lifetime_ || !iter_.iter()->IsKeyPinned() /* copy */); } if (ikey_.type == kTypeBlobIndex) { if (!SetBlobValueIfNeeded(ikey_.user_key, iter_.value())) { return false; } SetValueAndColumnsFromPlain(expose_blob_index_ ? iter_.value() : blob_value_); } else if (ikey_.type == kTypeWideColumnEntity) { if (!SetValueAndColumnsFromEntity(iter_.value())) { return false; } } else { assert(ikey_.type == kTypeValue); SetValueAndColumnsFromPlain(iter_.value()); } valid_ = true; return true; break; case kTypeMerge: if (!iter_.PrepareValue()) { assert(!iter_.status().ok()); valid_ = false; return false; } saved_key_.SetUserKey( ikey_.user_key, !pin_thru_lifetime_ || !iter_.iter()->IsKeyPinned() /* copy */); // 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: valid_ = false; status_ = Status::Corruption( "Unknown value type: " + std::to_string(static_cast(ikey_.type))); return false; } } } else { if (more_recent) { PERF_COUNTER_ADD(internal_recent_skipped_count, 1); } // This key was inserted after our snapshot was taken or skipped by // timestamp range. 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_.CompareWithoutTimestamp( ikey_.user_key, saved_key_.GetUserKey()); if (cmp == 0 || (skipping_saved_key && cmp < 0)) { num_skipped++; } else { saved_key_.SetUserKey( ikey_.user_key, !iter_.iter()->IsKeyPinned() || !pin_thru_lifetime_ /* copy */); skipping_saved_key = false; num_skipped = 0; reseek_done = false; } } // If we have sequentially iterated via numerous equal keys, then it's // better to seek so that we can avoid too many key comparisons. // // To avoid infinite loops, do not reseek if we have already attempted to // reseek previously. // // TODO(lth): If we reseek to sequence number greater than ikey_.sequence, // then it does not make sense to reseek as we would actually land further // away from the desired key. There is opportunity for optimization here. if (num_skipped > max_skip_ && !reseek_done) { is_key_seqnum_zero_ = false; num_skipped = 0; reseek_done = true; std::string last_key; if (skipping_saved_key) { // 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). if (timestamp_size_ == 0) { AppendInternalKey( &last_key, ParsedInternalKey(saved_key_.GetUserKey(), 0, kTypeDeletion)); } else { const std::string kTsMin(timestamp_size_, '\0'); AppendInternalKeyWithDifferentTimestamp( &last_key, ParsedInternalKey(saved_key_.GetUserKey(), 0, kTypeDeletion), kTsMin); } // Don't set skipping_saved_key = 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. if (timestamp_size_ == 0) { AppendInternalKey( &last_key, ParsedInternalKey(saved_key_.GetUserKey(), sequence_, kValueTypeForSeek)); } else { AppendInternalKeyWithDifferentTimestamp( &last_key, ParsedInternalKey(saved_key_.GetUserKey(), sequence_, kValueTypeForSeek), *timestamp_ub_); } } 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 // iter_.PrepareValue() has been called // 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_.iter()->IsValuePinned() /* operand_pinned */); PERF_COUNTER_ADD(internal_merge_count, 1); TEST_SYNC_POINT("DBIter::MergeValuesNewToOld:PushedFirstOperand"); ParsedInternalKey ikey; for (iter_.Next(); iter_.Valid(); iter_.Next()) { TEST_SYNC_POINT("DBIter::MergeValuesNewToOld:SteppedToNextOperand"); if (!ParseKey(&ikey)) { return false; } if (!user_comparator_.EqualWithoutTimestamp(ikey.user_key, saved_key_.GetUserKey())) { // hit the next user key, stop right here break; } if (kTypeDeletion == ikey.type || kTypeSingleDeletion == ikey.type || kTypeDeletionWithTimestamp == ikey.type) { // hit a delete with the same user key, stop right here // iter_ is positioned after delete iter_.Next(); break; } if (!iter_.PrepareValue()) { valid_ = false; return false; } 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(); if (!Merge(&val, ikey.user_key)) { 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_.iter()->IsValuePinned() /* operand_pinned */); PERF_COUNTER_ADD(internal_merge_count, 1); } else if (kTypeBlobIndex == ikey.type) { if (expose_blob_index_) { status_ = Status::NotSupported("BlobDB does not support merge operator."); valid_ = false; return false; } // hit a put, merge the put value with operands and store the // final result in saved_value_. We are done! if (!SetBlobValueIfNeeded(ikey.user_key, iter_.value())) { return false; } valid_ = true; if (!Merge(&blob_value_, ikey.user_key)) { return false; } ResetBlobValue(); // iter_ is positioned after put iter_.Next(); if (!iter_.status().ok()) { valid_ = false; return false; } return true; } else if (kTypeWideColumnEntity == ikey.type) { if (!MergeEntity(iter_.value(), ikey.user_key)) { return false; } // iter_ is positioned after put iter_.Next(); if (!iter_.status().ok()) { valid_ = false; return false; } return true; } else { valid_ = false; status_ = Status::Corruption( "Unrecognized value type: " + std::to_string(static_cast(ikey.type))); return 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. if (!Merge(nullptr, saved_key_.GetUserKey())) { return false; } assert(status_.ok()); return true; } void DBIter::Prev() { assert(valid_); assert(status_.ok()); PERF_COUNTER_ADD(iter_prev_count, 1); PERF_CPU_TIMER_GUARD(iter_prev_cpu_nanos, clock_); ReleaseTempPinnedData(); ResetBlobValue(); ResetValueAndColumns(); ResetInternalKeysSkippedCounter(); bool ok = true; if (direction_ == kForward) { if (!ReverseToBackward()) { ok = false; } } if (ok) { ClearSavedValue(); Slice prefix; if (prefix_same_as_start_) { assert(prefix_extractor_ != nullptr); prefix = prefix_.GetUserKey(); } PrevInternal(prefix_same_as_start_ ? &prefix : nullptr); } 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 (!expect_total_order_inner_iter() || !iter_.Valid()) { IterKey last_key; ParsedInternalKey pikey(saved_key_.GetUserKey(), kMaxSequenceNumber, kValueTypeForSeek); if (timestamp_size_ > 0) { // TODO: pre-create kTsMax. const std::string kTsMax(timestamp_size_, '\xff'); pikey.SetTimestamp(kTsMax); } last_key.SetInternalKey(pikey); iter_.Seek(last_key.GetInternalKey()); RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION); } 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_ && (!expect_total_order_inner_iter() || !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 (!expect_total_order_inner_iter()) { 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(); } } RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION); } direction_ = kReverse; return FindUserKeyBeforeSavedKey(); } void DBIter::PrevInternal(const Slice* prefix) { while (iter_.Valid()) { saved_key_.SetUserKey( ExtractUserKey(iter_.key()), !iter_.iter()->IsKeyPinned() || !pin_thru_lifetime_ /* copy */); assert(prefix == nullptr || prefix_extractor_ != nullptr); if (prefix != nullptr && prefix_extractor_ ->Transform(StripTimestampFromUserKey(saved_key_.GetUserKey(), timestamp_size_)) .compare(*prefix) != 0) { assert(prefix_same_as_start_); // Current key does not have the same prefix as start valid_ = false; return; } assert(iterate_lower_bound_ == nullptr || iter_.MayBeOutOfLowerBound() || user_comparator_.CompareWithoutTimestamp( saved_key_.GetUserKey(), /*a_has_ts=*/true, *iterate_lower_bound_, /*b_has_ts=*/false) >= 0); if (iterate_lower_bound_ != nullptr && iter_.MayBeOutOfLowerBound() && user_comparator_.CompareWithoutTimestamp( saved_key_.GetUserKey(), /*a_has_ts=*/true, *iterate_lower_bound_, /*b_has_ts=*/false) < 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, // kTypeDeletionWithTimestamp, kTypeSingleDeletion, kTypeValue, // kTypeBlobIndex, or kTypeWideColumnEntity) ValueType last_not_merge_type = kTypeDeletion; ValueType last_key_entry_type = kTypeDeletion; // If false, it indicates that we have not seen any valid entry, even though // last_key_entry_type is initialized to kTypeDeletion. bool valid_entry_seen = false; // 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 (!user_comparator_.EqualWithoutTimestamp(ikey.user_key, saved_key_.GetUserKey())) { // Found a smaller user key, thus we are done with current user key. break; } assert(ikey.user_key.size() >= timestamp_size_); Slice ts; if (timestamp_size_ > 0) { ts = Slice(ikey.user_key.data() + ikey.user_key.size() - timestamp_size_, timestamp_size_); } bool visible = IsVisible(ikey.sequence, ts); if (!visible && (timestamp_lb_ == nullptr || user_comparator_.CompareTimestamp(ts, *timestamp_ub_) > 0)) { // Found an invisible version of the current user key, and it must have // a higher sequence number or timestamp. Therefore, we are done with the // current user key. break; } if (!ts.empty()) { saved_timestamp_.assign(ts.data(), ts.size()); } 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_) { return FindValueForCurrentKeyUsingSeek(); } if (!iter_.PrepareValue()) { valid_ = false; return false; } if (timestamp_lb_ != nullptr) { // Only needed when timestamp_lb_ is not null [[maybe_unused]] const bool ret = ParseKey(&ikey_); // Since the preceding ParseKey(&ikey) succeeds, so must this. assert(ret); saved_key_.SetInternalKey(ikey); } else if (user_comparator_.Compare(ikey.user_key, saved_key_.GetUserKey()) < 0) { saved_key_.SetUserKey( ikey.user_key, !pin_thru_lifetime_ || !iter_.iter()->IsKeyPinned() /* copy */); } valid_entry_seen = true; last_key_entry_type = ikey.type; switch (last_key_entry_type) { case kTypeValue: case kTypeBlobIndex: case kTypeWideColumnEntity: if (iter_.iter()->IsValuePinned()) { pinned_value_ = iter_.value(); } else { valid_ = false; status_ = Status::NotSupported( "Backward iteration not supported if underlying iterator's value " "cannot be pinned."); } merge_context_.Clear(); last_not_merge_type = last_key_entry_type; if (!status_.ok()) { return false; } break; case kTypeDeletion: case kTypeDeletionWithTimestamp: case kTypeSingleDeletion: merge_context_.Clear(); last_not_merge_type = last_key_entry_type; PERF_COUNTER_ADD(internal_delete_skipped_count, 1); break; case kTypeMerge: { assert(merge_operator_ != nullptr); merge_context_.PushOperandBack( iter_.value(), iter_.iter()->IsValuePinned() /* operand_pinned */); PERF_COUNTER_ADD(internal_merge_count, 1); } break; default: valid_ = false; status_ = Status::Corruption( "Unknown value type: " + std::to_string(static_cast(last_key_entry_type))); return false; } PERF_COUNTER_ADD(internal_key_skipped_count, 1); iter_.Prev(); ++num_skipped; if (visible && timestamp_lb_ != nullptr) { // If timestamp_lb_ is not nullptr, we do not have to look further for // another internal key. We can return this current internal key. Yet we // still keep the invariant that iter_ is positioned before the returned // key. break; } } if (!iter_.status().ok()) { valid_ = false; return false; } if (!valid_entry_seen) { // Since we haven't seen any valid entry, last_key_entry_type remains // unchanged and the same as its initial value. assert(last_key_entry_type == kTypeDeletion); assert(last_not_merge_type == kTypeDeletion); valid_ = false; return true; } if (timestamp_lb_ != nullptr) { assert(last_key_entry_type == ikey_.type); } switch (last_key_entry_type) { case kTypeDeletion: case kTypeDeletionWithTimestamp: case kTypeSingleDeletion: if (timestamp_lb_ == nullptr) { valid_ = false; } else { valid_ = true; } return true; case kTypeMerge: current_entry_is_merged_ = true; if (last_not_merge_type == kTypeDeletion || last_not_merge_type == kTypeSingleDeletion || last_not_merge_type == kTypeDeletionWithTimestamp) { if (!Merge(nullptr, saved_key_.GetUserKey())) { return false; } return true; } else if (last_not_merge_type == kTypeBlobIndex) { if (expose_blob_index_) { status_ = Status::NotSupported("BlobDB does not support merge operator."); valid_ = false; return false; } if (!SetBlobValueIfNeeded(saved_key_.GetUserKey(), pinned_value_)) { return false; } valid_ = true; if (!Merge(&blob_value_, saved_key_.GetUserKey())) { return false; } ResetBlobValue(); return true; } else if (last_not_merge_type == kTypeWideColumnEntity) { if (!MergeEntity(pinned_value_, saved_key_.GetUserKey())) { return false; } return true; } else { assert(last_not_merge_type == kTypeValue); if (!Merge(&pinned_value_, saved_key_.GetUserKey())) { return false; } return true; } break; case kTypeValue: SetValueAndColumnsFromPlain(pinned_value_); break; case kTypeBlobIndex: if (!SetBlobValueIfNeeded(saved_key_.GetUserKey(), pinned_value_)) { return false; } SetValueAndColumnsFromPlain(expose_blob_index_ ? pinned_value_ : blob_value_); break; case kTypeWideColumnEntity: if (!SetValueAndColumnsFromEntity(pinned_value_)) { return false; } break; default: valid_ = false; status_ = Status::Corruption( "Unknown value type: " + std::to_string(static_cast(last_key_entry_type))); 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; if (0 == timestamp_size_) { AppendInternalKey(&last_key, ParsedInternalKey(saved_key_.GetUserKey(), sequence_, kValueTypeForSeek)); } else { AppendInternalKeyWithDifferentTimestamp( &last_key, ParsedInternalKey(saved_key_.GetUserKey(), sequence_, kValueTypeForSeek), timestamp_lb_ == nullptr ? *timestamp_ub_ : *timestamp_lb_); } 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; } assert(ikey.user_key.size() >= timestamp_size_); Slice ts; if (timestamp_size_ > 0) { ts = Slice(ikey.user_key.data() + ikey.user_key.size() - timestamp_size_, timestamp_size_); } if (!user_comparator_.EqualWithoutTimestamp(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, ts)) { break; } iter_.Next(); } if (ikey.type == kTypeDeletion || ikey.type == kTypeSingleDeletion || kTypeDeletionWithTimestamp == ikey.type) { if (timestamp_lb_ == nullptr) { valid_ = false; } else { valid_ = true; saved_key_.SetInternalKey(ikey); } return true; } if (!iter_.PrepareValue()) { valid_ = false; return false; } if (timestamp_size_ > 0) { Slice ts = ExtractTimestampFromUserKey(ikey.user_key, timestamp_size_); saved_timestamp_.assign(ts.data(), ts.size()); } if (ikey.type == kTypeValue || ikey.type == kTypeBlobIndex || ikey.type == kTypeWideColumnEntity) { assert(iter_.iter()->IsValuePinned()); pinned_value_ = iter_.value(); if (ikey.type == kTypeBlobIndex) { if (!SetBlobValueIfNeeded(ikey.user_key, pinned_value_)) { return false; } SetValueAndColumnsFromPlain(expose_blob_index_ ? pinned_value_ : blob_value_); } else if (ikey.type == kTypeWideColumnEntity) { if (!SetValueAndColumnsFromEntity(pinned_value_)) { return false; } } else { assert(ikey.type == kTypeValue); SetValueAndColumnsFromPlain(pinned_value_); } if (timestamp_lb_ != nullptr) { saved_key_.SetInternalKey(ikey); } 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_.iter()->IsValuePinned() /* operand_pinned */); PERF_COUNTER_ADD(internal_merge_count, 1); while (true) { iter_.Next(); if (!iter_.Valid()) { if (!iter_.status().ok()) { valid_ = false; return false; } break; } if (!ParseKey(&ikey)) { return false; } if (!user_comparator_.EqualWithoutTimestamp(ikey.user_key, saved_key_.GetUserKey())) { break; } if (ikey.type == kTypeDeletion || ikey.type == kTypeSingleDeletion || ikey.type == kTypeDeletionWithTimestamp) { break; } if (!iter_.PrepareValue()) { valid_ = false; return false; } if (ikey.type == kTypeValue) { const Slice val = iter_.value(); if (!Merge(&val, saved_key_.GetUserKey())) { return false; } return true; } else if (ikey.type == kTypeMerge) { merge_context_.PushOperand( iter_.value(), iter_.iter()->IsValuePinned() /* operand_pinned */); PERF_COUNTER_ADD(internal_merge_count, 1); } else if (ikey.type == kTypeBlobIndex) { if (expose_blob_index_) { status_ = Status::NotSupported("BlobDB does not support merge operator."); valid_ = false; return false; } if (!SetBlobValueIfNeeded(ikey.user_key, iter_.value())) { return false; } valid_ = true; if (!Merge(&blob_value_, saved_key_.GetUserKey())) { return false; } ResetBlobValue(); return true; } else if (ikey.type == kTypeWideColumnEntity) { if (!MergeEntity(iter_.value(), saved_key_.GetUserKey())) { return false; } return true; } else { valid_ = false; status_ = Status::Corruption( "Unknown value type: " + std::to_string(static_cast(ikey.type))); return false; } } if (!Merge(nullptr, saved_key_.GetUserKey())) { 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 (!expect_total_order_inner_iter() || !iter_.Valid()) { if (!expect_total_order_inner_iter()) { 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; } bool DBIter::Merge(const Slice* val, const Slice& user_key) { // `op_failure_scope` (an output parameter) is not provided (set to nullptr) // since a failure must be propagated regardless of its value. Status s = MergeHelper::TimedFullMerge( merge_operator_, user_key, val, merge_context_.GetOperands(), &saved_value_, logger_, statistics_, clock_, &pinned_value_, /* update_num_ops_stats */ true, /* op_failure_scope */ nullptr); if (!s.ok()) { valid_ = false; status_ = s; return false; } SetValueAndColumnsFromPlain(pinned_value_.data() ? pinned_value_ : saved_value_); valid_ = true; return true; } bool DBIter::MergeEntity(const Slice& entity, const Slice& user_key) { // `op_failure_scope` (an output parameter) is not provided (set to nullptr) // since a failure must be propagated regardless of its value. Status s = MergeHelper::TimedFullMergeWithEntity( merge_operator_, user_key, entity, merge_context_.GetOperands(), &saved_value_, logger_, statistics_, clock_, /* update_num_ops_stats */ true, /* op_failure_scope */ nullptr); if (!s.ok()) { valid_ = false; status_ = s; return false; } if (!SetValueAndColumnsFromEntity(saved_value_)) { return false; } 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 (CompareKeyForSkip(ikey.user_key, saved_key_.GetUserKey()) < 0) { return true; } if (TooManyInternalKeysSkipped()) { return false; } assert(ikey.sequence != kMaxSequenceNumber); assert(ikey.user_key.size() >= timestamp_size_); Slice ts; if (timestamp_size_ > 0) { ts = Slice(ikey.user_key.data() + ikey.user_key.size() - timestamp_size_, timestamp_size_); } if (!IsVisible(ikey.sequence, ts)) { PERF_COUNTER_ADD(internal_recent_skipped_count, 1); } else { PERF_COUNTER_ADD(internal_key_skipped_count, 1); } if (num_skipped >= max_skip_) { num_skipped = 0; IterKey last_key; ParsedInternalKey pikey(saved_key_.GetUserKey(), kMaxSequenceNumber, kValueTypeForSeek); if (timestamp_size_ > 0) { // TODO: pre-create kTsMax. const std::string kTsMax(timestamp_size_, '\xff'); pikey.SetTimestamp(kTsMax); } last_key.SetInternalKey(pikey); // 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, const Slice& ts, bool* more_recent) { // Remember that comparator orders preceding timestamp as larger. // TODO(yanqin): support timestamp in read_callback_. bool visible_by_seq = (read_callback_ == nullptr) ? sequence <= sequence_ : read_callback_->IsVisible(sequence); bool visible_by_ts = (timestamp_ub_ == nullptr || user_comparator_.CompareTimestamp(ts, *timestamp_ub_) <= 0) && (timestamp_lb_ == nullptr || user_comparator_.CompareTimestamp(ts, *timestamp_lb_) >= 0); if (more_recent) { *more_recent = !visible_by_seq; } return visible_by_seq && visible_by_ts; } void DBIter::SetSavedKeyToSeekTarget(const Slice& target) { is_key_seqnum_zero_ = false; SequenceNumber seq = sequence_; saved_key_.Clear(); saved_key_.SetInternalKey(target, seq, kValueTypeForSeek, timestamp_ub_); if (iterate_lower_bound_ != nullptr && user_comparator_.CompareWithoutTimestamp( saved_key_.GetUserKey(), /*a_has_ts=*/true, *iterate_lower_bound_, /*b_has_ts=*/false) < 0) { // Seek key is smaller than the lower bound. saved_key_.Clear(); saved_key_.SetInternalKey(*iterate_lower_bound_, seq, kValueTypeForSeek, timestamp_ub_); } } void DBIter::SetSavedKeyToSeekForPrevTarget(const Slice& target) { is_key_seqnum_zero_ = false; saved_key_.Clear(); // now saved_key is used to store internal key. saved_key_.SetInternalKey(target, 0 /* sequence_number */, kValueTypeForSeekForPrev, timestamp_ub_); if (timestamp_size_ > 0) { const std::string kTsMin(timestamp_size_, '\0'); Slice ts = kTsMin; saved_key_.UpdateInternalKey( /*seq=*/0, kValueTypeForSeekForPrev, timestamp_lb_ == nullptr ? &ts : timestamp_lb_); } if (iterate_upper_bound_ != nullptr && user_comparator_.CompareWithoutTimestamp( saved_key_.GetUserKey(), /*a_has_ts=*/true, *iterate_upper_bound_, /*b_has_ts=*/false) >= 0) { saved_key_.Clear(); saved_key_.SetInternalKey(*iterate_upper_bound_, kMaxSequenceNumber, kValueTypeForSeekForPrev, timestamp_ub_); if (timestamp_size_ > 0) { const std::string kTsMax(timestamp_size_, '\xff'); Slice ts = kTsMax; saved_key_.UpdateInternalKey(kMaxSequenceNumber, kValueTypeForSeekForPrev, &ts); } } } void DBIter::Seek(const Slice& target) { PERF_COUNTER_ADD(iter_seek_count, 1); PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, clock_); StopWatch sw(clock_, statistics_, DB_SEEK); if (db_impl_ != nullptr && cfd_ != nullptr) { // TODO: What do we do if this returns an error? Slice lower_bound, upper_bound; if (iterate_lower_bound_ != nullptr) { lower_bound = *iterate_lower_bound_; } else { lower_bound = Slice(""); } if (iterate_upper_bound_ != nullptr) { upper_bound = *iterate_upper_bound_; } else { upper_bound = Slice(""); } db_impl_->TraceIteratorSeek(cfd_->GetID(), target, lower_bound, upper_bound) .PermitUncheckedError(); } status_ = Status::OK(); ReleaseTempPinnedData(); ResetBlobValue(); ResetValueAndColumns(); ResetInternalKeysSkippedCounter(); // Seek the inner iterator based on the target key. { PERF_TIMER_GUARD(seek_internal_seek_time); SetSavedKeyToSeekTarget(target); iter_.Seek(saved_key_.GetInternalKey()); RecordTick(statistics_, NUMBER_DB_SEEK); } if (!iter_.Valid()) { valid_ = false; return; } direction_ = kForward; // Now the inner iterator is placed to the target position. From there, // we need to find out the next key that is visible to the user. ClearSavedValue(); if (prefix_same_as_start_) { // The case where the iterator needs to be invalidated if it has exhausted // keys within the same prefix of the seek key. assert(prefix_extractor_ != nullptr); Slice target_prefix = prefix_extractor_->Transform(target); FindNextUserEntry(false /* not skipping saved_key */, &target_prefix /* prefix */); if (valid_) { // Remember the prefix of the seek key for the future Next() call to // check. prefix_.SetUserKey(target_prefix); } } else { FindNextUserEntry(false /* not skipping saved_key */, nullptr); } if (!valid_) { return; } // Updating stats and perf context counters. if (statistics_ != nullptr) { // 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()); } void DBIter::SeekForPrev(const Slice& target) { PERF_COUNTER_ADD(iter_seek_count, 1); PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, clock_); StopWatch sw(clock_, statistics_, DB_SEEK); if (db_impl_ != nullptr && cfd_ != nullptr) { // TODO: What do we do if this returns an error? Slice lower_bound, upper_bound; if (iterate_lower_bound_ != nullptr) { lower_bound = *iterate_lower_bound_; } else { lower_bound = Slice(""); } if (iterate_upper_bound_ != nullptr) { upper_bound = *iterate_upper_bound_; } else { upper_bound = Slice(""); } db_impl_ ->TraceIteratorSeekForPrev(cfd_->GetID(), target, lower_bound, upper_bound) .PermitUncheckedError(); } status_ = Status::OK(); ReleaseTempPinnedData(); ResetBlobValue(); ResetValueAndColumns(); ResetInternalKeysSkippedCounter(); // Seek the inner iterator based on the target key. { PERF_TIMER_GUARD(seek_internal_seek_time); SetSavedKeyToSeekForPrevTarget(target); iter_.SeekForPrev(saved_key_.GetInternalKey()); RecordTick(statistics_, NUMBER_DB_SEEK); } if (!iter_.Valid()) { valid_ = false; return; } direction_ = kReverse; // Now the inner iterator is placed to the target position. From there, // we need to find out the first key that is visible to the user in the // backward direction. ClearSavedValue(); if (prefix_same_as_start_) { // The case where the iterator needs to be invalidated if it has exhausted // keys within the same prefix of the seek key. assert(prefix_extractor_ != nullptr); Slice target_prefix = prefix_extractor_->Transform(target); PrevInternal(&target_prefix); if (valid_) { // Remember the prefix of the seek key for the future Prev() call to // check. prefix_.SetUserKey(target_prefix); } } else { PrevInternal(nullptr); } // Report stats and perf context. if (statistics_ != nullptr && 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()); } } void DBIter::SeekToFirst() { if (iterate_lower_bound_ != nullptr) { Seek(*iterate_lower_bound_); return; } PERF_COUNTER_ADD(iter_seek_count, 1); PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, clock_); // Don't use iter_::Seek() if we set a prefix extractor // because prefix seek will be used. if (!expect_total_order_inner_iter()) { max_skip_ = std::numeric_limits::max(); } status_ = Status::OK(); // if iterator is empty, this status_ could be unchecked. status_.PermitUncheckedError(); direction_ = kForward; ReleaseTempPinnedData(); ResetBlobValue(); ResetValueAndColumns(); ResetInternalKeysSkippedCounter(); ClearSavedValue(); is_key_seqnum_zero_ = false; { PERF_TIMER_GUARD(seek_internal_seek_time); iter_.SeekToFirst(); } RecordTick(statistics_, NUMBER_DB_SEEK); if (iter_.Valid()) { saved_key_.SetUserKey( ExtractUserKey(iter_.key()), !iter_.iter()->IsKeyPinned() || !pin_thru_lifetime_ /* copy */); FindNextUserEntry(false /* not skipping saved_key */, nullptr /* 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_same_as_start_) { assert(prefix_extractor_ != nullptr); prefix_.SetUserKey(prefix_extractor_->Transform( StripTimestampFromUserKey(saved_key_.GetUserKey(), timestamp_size_))); } } void DBIter::SeekToLast() { if (iterate_upper_bound_ != nullptr) { // Seek to last key strictly less than ReadOptions.iterate_upper_bound. SeekForPrev(*iterate_upper_bound_); #ifndef NDEBUG Slice k = Valid() ? key() : Slice(); if (Valid() && timestamp_size_ > 0 && timestamp_lb_) { k.remove_suffix(kNumInternalBytes + timestamp_size_); } assert(!Valid() || user_comparator_.CompareWithoutTimestamp( k, /*a_has_ts=*/false, *iterate_upper_bound_, /*b_has_ts=*/false) < 0); #endif return; } PERF_COUNTER_ADD(iter_seek_count, 1); PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, clock_); // Don't use iter_::Seek() if we set a prefix extractor // because prefix seek will be used. if (!expect_total_order_inner_iter()) { max_skip_ = std::numeric_limits::max(); } status_ = Status::OK(); // if iterator is empty, this status_ could be unchecked. status_.PermitUncheckedError(); direction_ = kReverse; ReleaseTempPinnedData(); ResetBlobValue(); ResetValueAndColumns(); ResetInternalKeysSkippedCounter(); ClearSavedValue(); is_key_seqnum_zero_ = false; { PERF_TIMER_GUARD(seek_internal_seek_time); iter_.SeekToLast(); } PrevInternal(nullptr); 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_same_as_start_) { assert(prefix_extractor_ != nullptr); prefix_.SetUserKey(prefix_extractor_->Transform( StripTimestampFromUserKey(saved_key_.GetUserKey(), timestamp_size_))); } } Iterator* NewDBIterator(Env* env, const ReadOptions& read_options, const ImmutableOptions& ioptions, const MutableCFOptions& mutable_cf_options, const Comparator* user_key_comparator, InternalIterator* internal_iter, const Version* version, const SequenceNumber& sequence, uint64_t max_sequential_skip_in_iterations, ReadCallback* read_callback, DBImpl* db_impl, ColumnFamilyData* cfd, bool expose_blob_index) { DBIter* db_iter = new DBIter(env, read_options, ioptions, mutable_cf_options, user_key_comparator, internal_iter, version, sequence, false, max_sequential_skip_in_iterations, read_callback, db_impl, cfd, expose_blob_index); return db_iter; } } // namespace ROCKSDB_NAMESPACE