fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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424 lines
17 KiB
424 lines
17 KiB
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#include "db/merge_helper.h"
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#include <string>
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#include "db/dbformat.h"
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#include "monitoring/perf_context_imp.h"
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#include "monitoring/statistics.h"
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#include "port/likely.h"
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#include "rocksdb/comparator.h"
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#include "rocksdb/db.h"
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#include "rocksdb/merge_operator.h"
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#include "rocksdb/system_clock.h"
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#include "table/format.h"
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#include "table/internal_iterator.h"
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namespace ROCKSDB_NAMESPACE {
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MergeHelper::MergeHelper(Env* env, const Comparator* user_comparator,
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const MergeOperator* user_merge_operator,
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const CompactionFilter* compaction_filter,
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Logger* logger, bool assert_valid_internal_key,
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SequenceNumber latest_snapshot,
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const SnapshotChecker* snapshot_checker, int level,
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Statistics* stats,
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const std::atomic<bool>* shutting_down)
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: env_(env),
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clock_(env->GetSystemClock().get()),
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user_comparator_(user_comparator),
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user_merge_operator_(user_merge_operator),
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compaction_filter_(compaction_filter),
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shutting_down_(shutting_down),
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logger_(logger),
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assert_valid_internal_key_(assert_valid_internal_key),
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allow_single_operand_(false),
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latest_snapshot_(latest_snapshot),
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snapshot_checker_(snapshot_checker),
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level_(level),
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keys_(),
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filter_timer_(clock_),
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total_filter_time_(0U),
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stats_(stats) {
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assert(user_comparator_ != nullptr);
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if (user_merge_operator_) {
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allow_single_operand_ = user_merge_operator_->AllowSingleOperand();
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}
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}
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Status MergeHelper::TimedFullMerge(const MergeOperator* merge_operator,
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const Slice& key, const Slice* value,
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const std::vector<Slice>& operands,
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std::string* result, Logger* logger,
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Statistics* statistics, SystemClock* clock,
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Slice* result_operand,
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bool update_num_ops_stats) {
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assert(merge_operator != nullptr);
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if (operands.size() == 0) {
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assert(value != nullptr && result != nullptr);
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result->assign(value->data(), value->size());
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return Status::OK();
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}
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if (update_num_ops_stats) {
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RecordInHistogram(statistics, READ_NUM_MERGE_OPERANDS,
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static_cast<uint64_t>(operands.size()));
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}
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bool success;
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Slice tmp_result_operand(nullptr, 0);
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const MergeOperator::MergeOperationInput merge_in(key, value, operands,
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logger);
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MergeOperator::MergeOperationOutput merge_out(*result, tmp_result_operand);
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{
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// Setup to time the merge
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StopWatchNano timer(clock, statistics != nullptr);
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PERF_TIMER_GUARD(merge_operator_time_nanos);
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// Do the merge
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success = merge_operator->FullMergeV2(merge_in, &merge_out);
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if (tmp_result_operand.data()) {
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// FullMergeV2 result is an existing operand
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if (result_operand != nullptr) {
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*result_operand = tmp_result_operand;
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} else {
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result->assign(tmp_result_operand.data(), tmp_result_operand.size());
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}
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} else if (result_operand) {
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*result_operand = Slice(nullptr, 0);
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}
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RecordTick(statistics, MERGE_OPERATION_TOTAL_TIME,
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statistics ? timer.ElapsedNanos() : 0);
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}
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if (!success) {
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RecordTick(statistics, NUMBER_MERGE_FAILURES);
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return Status::Corruption("Error: Could not perform merge.");
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}
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return Status::OK();
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}
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// PRE: iter points to the first merge type entry
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// POST: iter points to the first entry beyond the merge process (or the end)
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// keys_, operands_ are updated to reflect the merge result.
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// keys_ stores the list of keys encountered while merging.
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// operands_ stores the list of merge operands encountered while merging.
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// keys_[i] corresponds to operands_[i] for each i.
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//
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// TODO: Avoid the snapshot stripe map lookup in CompactionRangeDelAggregator
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// and just pass the StripeRep corresponding to the stripe being merged.
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Status MergeHelper::MergeUntil(InternalIterator* iter,
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CompactionRangeDelAggregator* range_del_agg,
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const SequenceNumber stop_before,
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const bool at_bottom,
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const bool allow_data_in_errors) {
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// Get a copy of the internal key, before it's invalidated by iter->Next()
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// Also maintain the list of merge operands seen.
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assert(HasOperator());
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keys_.clear();
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merge_context_.Clear();
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has_compaction_filter_skip_until_ = false;
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assert(user_merge_operator_);
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bool first_key = true;
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// We need to parse the internal key again as the parsed key is
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// backed by the internal key!
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// Assume no internal key corruption as it has been successfully parsed
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// by the caller.
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// original_key_is_iter variable is just caching the information:
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// original_key_is_iter == (iter->key().ToString() == original_key)
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bool original_key_is_iter = true;
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std::string original_key = iter->key().ToString();
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// Important:
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// orig_ikey is backed by original_key if keys_.empty()
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// orig_ikey is backed by keys_.back() if !keys_.empty()
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ParsedInternalKey orig_ikey;
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Status s = ParseInternalKey(original_key, &orig_ikey, allow_data_in_errors);
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assert(s.ok());
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if (!s.ok()) return s;
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bool hit_the_next_user_key = false;
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for (; iter->Valid(); iter->Next(), original_key_is_iter = false) {
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if (IsShuttingDown()) {
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s = Status::ShutdownInProgress();
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return s;
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}
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ParsedInternalKey ikey;
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assert(keys_.size() == merge_context_.GetNumOperands());
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Status pik_status =
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ParseInternalKey(iter->key(), &ikey, allow_data_in_errors);
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if (!pik_status.ok()) {
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// stop at corrupted key
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if (assert_valid_internal_key_) {
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return pik_status;
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}
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break;
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} else if (first_key) {
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assert(user_comparator_->Equal(ikey.user_key, orig_ikey.user_key));
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first_key = false;
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} else if (!user_comparator_->Equal(ikey.user_key, orig_ikey.user_key)) {
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// hit a different user key, stop right here
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hit_the_next_user_key = true;
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break;
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} else if (stop_before > 0 && ikey.sequence <= stop_before &&
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LIKELY(snapshot_checker_ == nullptr ||
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snapshot_checker_->CheckInSnapshot(ikey.sequence,
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stop_before) !=
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SnapshotCheckerResult::kNotInSnapshot)) {
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// hit an entry that's possibly visible by the previous snapshot, can't
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// touch that
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break;
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}
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// At this point we are guaranteed that we need to process this key.
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assert(IsValueType(ikey.type));
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if (ikey.type != kTypeMerge) {
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// hit a put/delete/single delete
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// => merge the put value or a nullptr with operands_
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// => store result in operands_.back() (and update keys_.back())
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// => change the entry type to kTypeValue for keys_.back()
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// We are done! Success!
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// If there are no operands, just return the Status::OK(). That will cause
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// the compaction iterator to write out the key we're currently at, which
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// is the put/delete we just encountered.
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if (keys_.empty()) {
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return s;
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}
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// TODO(noetzli) If the merge operator returns false, we are currently
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// (almost) silently dropping the put/delete. That's probably not what we
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// want. Also if we're in compaction and it's a put, it would be nice to
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// run compaction filter on it.
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const Slice val = iter->value();
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const Slice* val_ptr;
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if (kTypeValue == ikey.type &&
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(range_del_agg == nullptr ||
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!range_del_agg->ShouldDelete(
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ikey, RangeDelPositioningMode::kForwardTraversal))) {
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val_ptr = &val;
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} else {
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val_ptr = nullptr;
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}
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std::string merge_result;
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s = TimedFullMerge(user_merge_operator_, ikey.user_key, val_ptr,
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merge_context_.GetOperands(), &merge_result, logger_,
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stats_, clock_);
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// We store the result in keys_.back() and operands_.back()
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// if nothing went wrong (i.e.: no operand corruption on disk)
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if (s.ok()) {
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// The original key encountered
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original_key = std::move(keys_.back());
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orig_ikey.type = kTypeValue;
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UpdateInternalKey(&original_key, orig_ikey.sequence, orig_ikey.type);
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keys_.clear();
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merge_context_.Clear();
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keys_.emplace_front(std::move(original_key));
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merge_context_.PushOperand(merge_result);
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}
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// move iter to the next entry
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iter->Next();
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return s;
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} else {
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// hit a merge
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// => if there is a compaction filter, apply it.
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// => check for range tombstones covering the operand
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// => merge the operand into the front of the operands_ list
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// if not filtered
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// => then continue because we haven't yet seen a Put/Delete.
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//
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// Keep queuing keys and operands until we either meet a put / delete
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// request or later did a partial merge.
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Slice value_slice = iter->value();
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// add an operand to the list if:
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// 1) it's included in one of the snapshots. in that case we *must* write
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// it out, no matter what compaction filter says
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// 2) it's not filtered by a compaction filter
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CompactionFilter::Decision filter =
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ikey.sequence <= latest_snapshot_
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? CompactionFilter::Decision::kKeep
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: FilterMerge(orig_ikey.user_key, value_slice);
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if (filter != CompactionFilter::Decision::kRemoveAndSkipUntil &&
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range_del_agg != nullptr &&
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range_del_agg->ShouldDelete(
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iter->key(), RangeDelPositioningMode::kForwardTraversal)) {
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filter = CompactionFilter::Decision::kRemove;
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}
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if (filter == CompactionFilter::Decision::kKeep ||
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filter == CompactionFilter::Decision::kChangeValue) {
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if (original_key_is_iter) {
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// this is just an optimization that saves us one memcpy
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keys_.push_front(std::move(original_key));
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} else {
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keys_.push_front(iter->key().ToString());
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}
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if (keys_.size() == 1) {
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// we need to re-anchor the orig_ikey because it was anchored by
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// original_key before
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pik_status =
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ParseInternalKey(keys_.back(), &orig_ikey, allow_data_in_errors);
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pik_status.PermitUncheckedError();
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assert(pik_status.ok());
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}
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if (filter == CompactionFilter::Decision::kKeep) {
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merge_context_.PushOperand(
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value_slice, iter->IsValuePinned() /* operand_pinned */);
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} else { // kChangeValue
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// Compaction filter asked us to change the operand from value_slice
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// to compaction_filter_value_.
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merge_context_.PushOperand(compaction_filter_value_, false);
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}
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} else if (filter == CompactionFilter::Decision::kRemoveAndSkipUntil) {
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// Compaction filter asked us to remove this key altogether
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// (not just this operand), along with some keys following it.
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keys_.clear();
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merge_context_.Clear();
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has_compaction_filter_skip_until_ = true;
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return s;
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}
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}
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}
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if (merge_context_.GetNumOperands() == 0) {
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// we filtered out all the merge operands
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return s;
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}
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// We are sure we have seen this key's entire history if:
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// at_bottom == true (this does not necessarily mean it is the bottommost
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// layer, but rather that we are confident the key does not appear on any of
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// the lower layers, at_bottom == false doesn't mean it does appear, just
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// that we can't be sure, see Compaction::IsBottommostLevel for details)
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// AND
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// we have either encountered another key or end of key history on this
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// layer.
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//
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// When these conditions are true we are able to merge all the keys
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// using full merge.
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//
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// For these cases we are not sure about, we simply miss the opportunity
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// to combine the keys. Since VersionSet::SetupOtherInputs() always makes
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// sure that all merge-operands on the same level get compacted together,
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// this will simply lead to these merge operands moving to the next level.
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bool surely_seen_the_beginning =
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(hit_the_next_user_key || !iter->Valid()) && at_bottom;
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if (surely_seen_the_beginning) {
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// do a final merge with nullptr as the existing value and say
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// bye to the merge type (it's now converted to a Put)
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assert(kTypeMerge == orig_ikey.type);
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assert(merge_context_.GetNumOperands() >= 1);
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assert(merge_context_.GetNumOperands() == keys_.size());
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std::string merge_result;
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s = TimedFullMerge(user_merge_operator_, orig_ikey.user_key, nullptr,
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merge_context_.GetOperands(), &merge_result, logger_,
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stats_, clock_);
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if (s.ok()) {
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// The original key encountered
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// We are certain that keys_ is not empty here (see assertions couple of
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// lines before).
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original_key = std::move(keys_.back());
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orig_ikey.type = kTypeValue;
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UpdateInternalKey(&original_key, orig_ikey.sequence, orig_ikey.type);
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keys_.clear();
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merge_context_.Clear();
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keys_.emplace_front(std::move(original_key));
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merge_context_.PushOperand(merge_result);
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}
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} else {
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// We haven't seen the beginning of the key nor a Put/Delete.
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// Attempt to use the user's associative merge function to
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// merge the stacked merge operands into a single operand.
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s = Status::MergeInProgress();
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if (merge_context_.GetNumOperands() >= 2 ||
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(allow_single_operand_ && merge_context_.GetNumOperands() == 1)) {
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bool merge_success = false;
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std::string merge_result;
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{
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StopWatchNano timer(clock_, stats_ != nullptr);
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PERF_TIMER_GUARD(merge_operator_time_nanos);
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merge_success = user_merge_operator_->PartialMergeMulti(
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orig_ikey.user_key,
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std::deque<Slice>(merge_context_.GetOperands().begin(),
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merge_context_.GetOperands().end()),
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&merge_result, logger_);
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RecordTick(stats_, MERGE_OPERATION_TOTAL_TIME,
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stats_ ? timer.ElapsedNanosSafe() : 0);
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}
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if (merge_success) {
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// Merging of operands (associative merge) was successful.
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// Replace operands with the merge result
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merge_context_.Clear();
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merge_context_.PushOperand(merge_result);
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keys_.erase(keys_.begin(), keys_.end() - 1);
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}
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}
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}
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return s;
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}
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MergeOutputIterator::MergeOutputIterator(const MergeHelper* merge_helper)
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: merge_helper_(merge_helper) {
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it_keys_ = merge_helper_->keys().rend();
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it_values_ = merge_helper_->values().rend();
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}
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void MergeOutputIterator::SeekToFirst() {
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const auto& keys = merge_helper_->keys();
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const auto& values = merge_helper_->values();
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assert(keys.size() == values.size());
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it_keys_ = keys.rbegin();
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it_values_ = values.rbegin();
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}
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void MergeOutputIterator::Next() {
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++it_keys_;
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++it_values_;
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}
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CompactionFilter::Decision MergeHelper::FilterMerge(const Slice& user_key,
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const Slice& value_slice) {
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if (compaction_filter_ == nullptr) {
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return CompactionFilter::Decision::kKeep;
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}
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if (stats_ != nullptr && ShouldReportDetailedTime(env_, stats_)) {
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filter_timer_.Start();
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}
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compaction_filter_value_.clear();
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compaction_filter_skip_until_.Clear();
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auto ret = compaction_filter_->FilterV2(
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level_, user_key, CompactionFilter::ValueType::kMergeOperand, value_slice,
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&compaction_filter_value_, compaction_filter_skip_until_.rep());
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if (ret == CompactionFilter::Decision::kRemoveAndSkipUntil) {
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if (user_comparator_->Compare(*compaction_filter_skip_until_.rep(),
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user_key) <= 0) {
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// Invalid skip_until returned from compaction filter.
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// Keep the key as per FilterV2 documentation.
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ret = CompactionFilter::Decision::kKeep;
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} else {
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compaction_filter_skip_until_.ConvertFromUserKey(kMaxSequenceNumber,
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kValueTypeForSeek);
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}
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}
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if (stats_ != nullptr && ShouldReportDetailedTime(env_, stats_)) {
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total_filter_time_ += filter_timer_.ElapsedNanosSafe();
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}
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return ret;
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}
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} // namespace ROCKSDB_NAMESPACE
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