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Diffstat (limited to 'src/rocksdb/db/db_iter.cc')
| -rw-r--r-- | src/rocksdb/db/db_iter.cc | 1310 |
1 files changed, 1310 insertions, 0 deletions
diff --git a/src/rocksdb/db/db_iter.cc b/src/rocksdb/db/db_iter.cc new file mode 100644 index 000000000..e5d402948 --- /dev/null +++ b/src/rocksdb/db/db_iter.cc @@ -0,0 +1,1310 @@ +// 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 "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 "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 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) + : prefix_extractor_(mutable_cf_options.prefix_extractor.get()), + 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), + 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), + 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); + 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()) { + iter_.iter()->SetPinnedItersMgr(&pinned_iters_mgr_); + } +} + +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) { + 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(); + 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()) { + Slice prefix; + if (prefix_same_as_start_) { + assert(prefix_extractor_ != nullptr); + prefix = prefix_.GetUserKey(); + } + FindNextUserEntry(true /* skipping the current user key */, + prefix_same_as_start_ ? &prefix : 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()); + } +} + +// 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; + + is_blob_ = 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; + } + + is_key_seqnum_zero_ = (ikey_.sequence == 0); + + assert(iterate_upper_bound_ == nullptr || iter_.MayBeOutOfUpperBound() || + user_comparator_.Compare(ikey_.user_key, *iterate_upper_bound_) < 0); + if (iterate_upper_bound_ != nullptr && iter_.MayBeOutOfUpperBound() && + user_comparator_.Compare(ikey_.user_key, *iterate_upper_bound_) >= 0) { + break; + } + + assert(prefix == nullptr || prefix_extractor_ != nullptr); + if (prefix != nullptr && + prefix_extractor_->Transform(ikey_.user_key).compare(*prefix) != 0) { + assert(prefix_same_as_start_); + break; + } + + if (TooManyInternalKeysSkipped()) { + return false; + } + + if (IsVisible(ikey_.sequence)) { + // 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. + if (!is_prev_key_seqnum_zero && skipping_saved_key && + user_comparator_.Compare(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 || + user_comparator_.Compare(ikey_.user_key, + saved_key_.GetUserKey()) > 0); + num_skipped = 0; + reseek_done = false; + 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_.iter()->IsKeyPinned() /* copy */); + skipping_saved_key = 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); + 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 + saved_key_.SetUserKey( + ikey_.user_key, + !pin_thru_lifetime_ || + !iter_.iter()->IsKeyPinned() /* copy */); + skipping_saved_key = true; + } + } else { + saved_key_.SetUserKey( + ikey_.user_key, !pin_thru_lifetime_ || + !iter_.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_saved_key = true; + num_skipped = 0; + reseek_done = false; + 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_NAMESPACE::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_.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_saved_key = true; + num_skipped = 0; + reseek_done = false; + 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_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). + AppendInternalKey(&last_key, ParsedInternalKey(saved_key_.GetUserKey(), + 0, kTypeDeletion)); + // 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. + 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_.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_.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_NAMESPACE::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) { + 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; + 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_ && + (!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(); + } + } + } + + 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(saved_key_.GetUserKey()) + .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_.Compare(saved_key_.GetUserKey(), + *iterate_lower_bound_) >= 0); + if (iterate_lower_bound_ != nullptr && iter_.MayBeOutOfLowerBound() && + 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_) { + 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_.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_.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_NAMESPACE::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_NAMESPACE::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; + is_blob_ = false; + 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_NAMESPACE::blob_db::BlobDB instead."); + valid_ = false; + return false; + } + if (ikey.type == kTypeValue || ikey.type == kTypeBlobIndex) { + assert(iter_.iter()->IsValuePinned()); + pinned_value_ = iter_.value(); + is_blob_ = (ikey.type == kTypeBlobIndex); + 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 */); + 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_.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_NAMESPACE::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 (!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; +} + +// 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_) { + 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); + } +} + +void DBIter::SetSavedKeyToSeekTarget(const Slice& target) { + is_key_seqnum_zero_ = false; + SequenceNumber seq = sequence_; + saved_key_.Clear(); + saved_key_.SetInternalKey(target, seq); + + if (iterate_lower_bound_ != nullptr && + user_comparator_.Compare(saved_key_.GetUserKey(), *iterate_lower_bound_) < + 0) { + // Seek key is smaller than the lower bound. + saved_key_.Clear(); + saved_key_.SetInternalKey(*iterate_lower_bound_, seq); + } +} + +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); + + 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); + } +} + +void DBIter::Seek(const Slice& target) { + PERF_CPU_TIMER_GUARD(iter_seek_cpu_nanos, env_); + StopWatch sw(env_, statistics_, DB_SEEK); + +#ifndef ROCKSDB_LITE + if (db_impl_ != nullptr && cfd_ != nullptr) { + db_impl_->TraceIteratorSeek(cfd_->GetID(), target); + } +#endif // ROCKSDB_LITE + + status_ = Status::OK(); + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + + // Seek the inner iterator based on the target key. + { + PERF_TIMER_GUARD(seek_internal_seek_time); + + SetSavedKeyToSeekTarget(target); + iter_.Seek(saved_key_.GetInternalKey()); + + range_del_agg_.InvalidateRangeDelMapPositions(); + 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 exausted + // 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_CPU_TIMER_GUARD(iter_seek_cpu_nanos, env_); + StopWatch sw(env_, statistics_, DB_SEEK); + +#ifndef ROCKSDB_LITE + if (db_impl_ != nullptr && cfd_ != nullptr) { + db_impl_->TraceIteratorSeekForPrev(cfd_->GetID(), target); + } +#endif // ROCKSDB_LITE + + status_ = Status::OK(); + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + + // Seek the inner iterator based on the target key. + { + PERF_TIMER_GUARD(seek_internal_seek_time); + SetSavedKeyToSeekForPrevTarget(target); + iter_.SeekForPrev(saved_key_.GetInternalKey()); + range_del_agg_.InvalidateRangeDelMapPositions(); + 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 exausted + // 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_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 (!expect_total_order_inner_iter()) { + max_skip_ = std::numeric_limits<uint64_t>::max(); + } + status_ = Status::OK(); + direction_ = kForward; + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + ClearSavedValue(); + is_key_seqnum_zero_ = false; + + { + 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_.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(saved_key_.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(nullptr); + } + 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 (!expect_total_order_inner_iter()) { + max_skip_ = std::numeric_limits<uint64_t>::max(); + } + status_ = Status::OK(); + direction_ = kReverse; + ReleaseTempPinnedData(); + ResetInternalKeysSkippedCounter(); + ClearSavedValue(); + is_key_seqnum_zero_ = false; + + { + PERF_TIMER_GUARD(seek_internal_seek_time); + iter_.SeekToLast(); + range_del_agg_.InvalidateRangeDelMapPositions(); + } + 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(saved_key_.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; +} + +} // namespace ROCKSDB_NAMESPACE |