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rocksdb/utilities/agg_merge/agg_merge.cc

239 lines
7.3 KiB

// Copyright (c) 2017-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).
#include "utilities/agg_merge/agg_merge.h"
#include <assert.h>
#include <deque>
#include <memory>
#include <type_traits>
#include <utility>
#include <vector>
#include "port/lang.h"
#include "port/likely.h"
#include "rocksdb/merge_operator.h"
#include "rocksdb/slice.h"
#include "rocksdb/utilities/agg_merge.h"
#include "rocksdb/utilities/options_type.h"
#include "util/coding.h"
#include "utilities/merge_operators.h"
namespace ROCKSDB_NAMESPACE {
static std::unordered_map<std::string, std::unique_ptr<Aggregator>> func_map;
const std::string kUnnamedFuncName = "";
const std::string kErrorFuncName = "kErrorFuncName";
Status AddAggregator(const std::string& function_name,
std::unique_ptr<Aggregator>&& agg) {
if (function_name == kErrorFuncName) {
return Status::InvalidArgument(
"Cannot register function name kErrorFuncName");
}
func_map.emplace(function_name, std::move(agg));
return Status::OK();
}
AggMergeOperator::AggMergeOperator() {}
std::string EncodeAggFuncAndPayloadNoCheck(const Slice& function_name,
const Slice& value) {
std::string result;
PutLengthPrefixedSlice(&result, function_name);
result += value.ToString();
return result;
}
Status EncodeAggFuncAndPayload(const Slice& function_name, const Slice& payload,
std::string& output) {
if (function_name == kErrorFuncName) {
return Status::InvalidArgument("Cannot use error function name");
}
if (function_name != kUnnamedFuncName &&
func_map.find(function_name.ToString()) == func_map.end()) {
return Status::InvalidArgument("Function name not registered");
}
output = EncodeAggFuncAndPayloadNoCheck(function_name, payload);
return Status::OK();
}
bool ExtractAggFuncAndValue(const Slice& op, Slice& func, Slice& value) {
value = op;
return GetLengthPrefixedSlice(&value, &func);
}
bool ExtractList(const Slice& encoded_list, std::vector<Slice>& decoded_list) {
decoded_list.clear();
Slice list_slice = encoded_list;
Slice item;
while (GetLengthPrefixedSlice(&list_slice, &item)) {
decoded_list.push_back(item);
}
return list_slice.empty();
}
class AggMergeOperator::Accumulator {
public:
bool Add(const Slice& op, bool is_partial_aggregation) {
if (ignore_operands_) {
return true;
}
Slice my_func;
Slice my_value;
bool ret = ExtractAggFuncAndValue(op, my_func, my_value);
if (!ret) {
ignore_operands_ = true;
return true;
}
// Determine whether we need to do partial merge.
if (is_partial_aggregation && !my_func.empty()) {
auto f = func_map.find(my_func.ToString());
if (f == func_map.end() || !f->second->DoPartialAggregate()) {
return false;
}
}
if (!func_valid_) {
if (my_func != kUnnamedFuncName) {
func_ = my_func;
func_valid_ = true;
}
} else if (func_ != my_func) {
// User switched aggregation function. Need to aggregate the older
// one first.
// Previous aggreagion can't be done in partial merge
if (is_partial_aggregation) {
func_valid_ = false;
ignore_operands_ = true;
return false;
}
// We could consider stashing an iterator into the hash of aggregators
// to avoid repeated lookups when the aggregator doesn't change.
auto f = func_map.find(func_.ToString());
if (f == func_map.end() || !f->second->Aggregate(values_, scratch_)) {
func_valid_ = false;
ignore_operands_ = true;
return true;
}
std::swap(scratch_, aggregated_);
values_.clear();
values_.push_back(aggregated_);
func_ = my_func;
}
values_.push_back(my_value);
return true;
}
// Return false if aggregation fails.
// One possible reason
bool GetResult(std::string& result) {
if (!func_valid_) {
return false;
}
auto f = func_map.find(func_.ToString());
if (f == func_map.end()) {
return false;
}
if (!f->second->Aggregate(values_, scratch_)) {
return false;
}
result = EncodeAggFuncAndPayloadNoCheck(func_, scratch_);
return true;
}
void Clear() {
func_.clear();
values_.clear();
aggregated_.clear();
scratch_.clear();
ignore_operands_ = false;
func_valid_ = false;
}
private:
Slice func_;
std::vector<Slice> values_;
std::string aggregated_;
std::string scratch_;
bool ignore_operands_ = false;
bool func_valid_ = false;
};
// Creating and using a new Accumulator might invoke multiple malloc and is
// expensive if it needs to be done when processing each merge operation.
// AggMergeOperator's merge operators can be invoked concurrently by multiple
// threads so we cannot simply create one Aggregator and reuse.
// We use thread local instances instead.
AggMergeOperator::Accumulator& AggMergeOperator::GetTLSAccumulator() {
static thread_local Accumulator tls_acc;
tls_acc.Clear();
return tls_acc;
}
void AggMergeOperator::PackAllMergeOperands(const MergeOperationInput& merge_in,
MergeOperationOutput& merge_out) {
merge_out.new_value = "";
PutLengthPrefixedSlice(&merge_out.new_value, kErrorFuncName);
if (merge_in.existing_value != nullptr) {
PutLengthPrefixedSlice(&merge_out.new_value, *merge_in.existing_value);
}
for (const Slice& op : merge_in.operand_list) {
PutLengthPrefixedSlice(&merge_out.new_value, op);
}
}
bool AggMergeOperator::FullMergeV2(const MergeOperationInput& merge_in,
MergeOperationOutput* merge_out) const {
Accumulator& agg = GetTLSAccumulator();
if (merge_in.existing_value != nullptr) {
agg.Add(*merge_in.existing_value, /*is_partial_aggregation=*/false);
}
for (const Slice& e : merge_in.operand_list) {
agg.Add(e, /*is_partial_aggregation=*/false);
}
bool succ = agg.GetResult(merge_out->new_value);
if (!succ) {
// If aggregation can't happen, pack all merge operands. In contrast to
// merge operator, we don't want to fail the DB. If users insert wrong
// format or call unregistered an aggregation function, we still hope
// the DB can continue functioning with other keys.
PackAllMergeOperands(merge_in, *merge_out);
}
agg.Clear();
return true;
}
bool AggMergeOperator::PartialMergeMulti(const Slice& /*key*/,
const std::deque<Slice>& operand_list,
std::string* new_value,
Logger* /*logger*/) const {
Accumulator& agg = GetTLSAccumulator();
bool do_aggregation = true;
for (const Slice& item : operand_list) {
do_aggregation = agg.Add(item, /*is_partial_aggregation=*/true);
if (!do_aggregation) {
break;
}
}
if (do_aggregation) {
do_aggregation = agg.GetResult(*new_value);
}
agg.Clear();
return do_aggregation;
}
std::shared_ptr<MergeOperator> GetAggMergeOperator() {
STATIC_AVOID_DESTRUCTION(std::shared_ptr<MergeOperator>, instance)
(std::make_shared<AggMergeOperator>());
assert(instance);
return instance;
}
} // namespace ROCKSDB_NAMESPACE