rocksdb/table/table_reader_bench.cc
Vijay Nadimpalli d150e01474 New API to get all merge operands for a Key (#5604)
Summary:
This is a new API added to db.h to allow for fetching all merge operands associated with a Key. The main motivation for this API is to support use cases where doing a full online merge is not necessary as it is performance sensitive. Example use-cases:
1. Update subset of columns and read subset of columns -
Imagine a SQL Table, a row is encoded as a K/V pair (as it is done in MyRocks). If there are many columns and users only updated one of them, we can use merge operator to reduce write amplification. While users only read one or two columns in the read query, this feature can avoid a full merging of the whole row, and save some CPU.
2. Updating very few attributes in a value which is a JSON-like document -
Updating one attribute can be done efficiently using merge operator, while reading back one attribute can be done more efficiently if we don't need to do a full merge.
----------------------------------------------------------------------------------------------------
API :
Status GetMergeOperands(
      const ReadOptions& options, ColumnFamilyHandle* column_family,
      const Slice& key, PinnableSlice* merge_operands,
      GetMergeOperandsOptions* get_merge_operands_options,
      int* number_of_operands)

Example usage :
int size = 100;
int number_of_operands = 0;
std::vector<PinnableSlice> values(size);
GetMergeOperandsOptions merge_operands_info;
db_->GetMergeOperands(ReadOptions(), db_->DefaultColumnFamily(), "k1", values.data(), merge_operands_info, &number_of_operands);

Description :
Returns all the merge operands corresponding to the key. If the number of merge operands in DB is greater than merge_operands_options.expected_max_number_of_operands no merge operands are returned and status is Incomplete. Merge operands returned are in the order of insertion.
merge_operands-> Points to an array of at-least merge_operands_options.expected_max_number_of_operands and the caller is responsible for allocating it. If the status returned is Incomplete then number_of_operands will contain the total number of merge operands found in DB for key.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5604

Test Plan:
Added unit test and perf test in db_bench that can be run using the command:
./db_bench -benchmarks=getmergeoperands --merge_operator=sortlist

Differential Revision: D16657366

Pulled By: vjnadimpalli

fbshipit-source-id: 0faadd752351745224ee12d4ae9ef3cb529951bf
2019-08-06 14:26:44 -07:00

346 lines
13 KiB
C++

// 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).
#ifndef GFLAGS
#include <cstdio>
int main() {
fprintf(stderr, "Please install gflags to run rocksdb tools\n");
return 1;
}
#else
#include "db/db_impl/db_impl.h"
#include "db/dbformat.h"
#include "monitoring/histogram.h"
#include "rocksdb/db.h"
#include "rocksdb/slice_transform.h"
#include "rocksdb/table.h"
#include "table/block_based/block_based_table_factory.h"
#include "table/get_context.h"
#include "table/internal_iterator.h"
#include "table/plain/plain_table_factory.h"
#include "table/table_builder.h"
#include "test_util/testharness.h"
#include "test_util/testutil.h"
#include "util/file_reader_writer.h"
#include "util/gflags_compat.h"
using GFLAGS_NAMESPACE::ParseCommandLineFlags;
using GFLAGS_NAMESPACE::SetUsageMessage;
namespace rocksdb {
namespace {
// Make a key that i determines the first 4 characters and j determines the
// last 4 characters.
static std::string MakeKey(int i, int j, bool through_db) {
char buf[100];
snprintf(buf, sizeof(buf), "%04d__key___%04d", i, j);
if (through_db) {
return std::string(buf);
}
// If we directly query table, which operates on internal keys
// instead of user keys, we need to add 8 bytes of internal
// information (row type etc) to user key to make an internal
// key.
InternalKey key(std::string(buf), 0, ValueType::kTypeValue);
return key.Encode().ToString();
}
uint64_t Now(Env* env, bool measured_by_nanosecond) {
return measured_by_nanosecond ? env->NowNanos() : env->NowMicros();
}
} // namespace
// A very simple benchmark that.
// Create a table with roughly numKey1 * numKey2 keys,
// where there are numKey1 prefixes of the key, each has numKey2 number of
// distinguished key, differing in the suffix part.
// If if_query_empty_keys = false, query the existing keys numKey1 * numKey2
// times randomly.
// If if_query_empty_keys = true, query numKey1 * numKey2 random empty keys.
// Print out the total time.
// If through_db=true, a full DB will be created and queries will be against
// it. Otherwise, operations will be directly through table level.
//
// If for_terator=true, instead of just query one key each time, it queries
// a range sharing the same prefix.
namespace {
void TableReaderBenchmark(Options& opts, EnvOptions& env_options,
ReadOptions& read_options, int num_keys1,
int num_keys2, int num_iter, int /*prefix_len*/,
bool if_query_empty_keys, bool for_iterator,
bool through_db, bool measured_by_nanosecond) {
rocksdb::InternalKeyComparator ikc(opts.comparator);
std::string file_name =
test::PerThreadDBPath("rocksdb_table_reader_benchmark");
std::string dbname = test::PerThreadDBPath("rocksdb_table_reader_bench_db");
WriteOptions wo;
Env* env = Env::Default();
TableBuilder* tb = nullptr;
DB* db = nullptr;
Status s;
const ImmutableCFOptions ioptions(opts);
const ColumnFamilyOptions cfo(opts);
const MutableCFOptions moptions(cfo);
std::unique_ptr<WritableFileWriter> file_writer;
if (!through_db) {
std::unique_ptr<WritableFile> file;
env->NewWritableFile(file_name, &file, env_options);
std::vector<std::unique_ptr<IntTblPropCollectorFactory> >
int_tbl_prop_collector_factories;
file_writer.reset(
new WritableFileWriter(std::move(file), file_name, env_options));
int unknown_level = -1;
tb = opts.table_factory->NewTableBuilder(
TableBuilderOptions(
ioptions, moptions, ikc, &int_tbl_prop_collector_factories,
CompressionType::kNoCompression, 0 /* sample_for_compression */,
CompressionOptions(), false /* skip_filters */,
kDefaultColumnFamilyName, unknown_level),
0 /* column_family_id */, file_writer.get());
} else {
s = DB::Open(opts, dbname, &db);
ASSERT_OK(s);
ASSERT_TRUE(db != nullptr);
}
// Populate slightly more than 1M keys
for (int i = 0; i < num_keys1; i++) {
for (int j = 0; j < num_keys2; j++) {
std::string key = MakeKey(i * 2, j, through_db);
if (!through_db) {
tb->Add(key, key);
} else {
db->Put(wo, key, key);
}
}
}
if (!through_db) {
tb->Finish();
file_writer->Close();
} else {
db->Flush(FlushOptions());
}
std::unique_ptr<TableReader> table_reader;
if (!through_db) {
std::unique_ptr<RandomAccessFile> raf;
s = env->NewRandomAccessFile(file_name, &raf, env_options);
if (!s.ok()) {
fprintf(stderr, "Create File Error: %s\n", s.ToString().c_str());
exit(1);
}
uint64_t file_size;
env->GetFileSize(file_name, &file_size);
std::unique_ptr<RandomAccessFileReader> file_reader(
new RandomAccessFileReader(std::move(raf), file_name));
s = opts.table_factory->NewTableReader(
TableReaderOptions(ioptions, moptions.prefix_extractor.get(),
env_options, ikc),
std::move(file_reader), file_size, &table_reader);
if (!s.ok()) {
fprintf(stderr, "Open Table Error: %s\n", s.ToString().c_str());
exit(1);
}
}
Random rnd(301);
std::string result;
HistogramImpl hist;
for (int it = 0; it < num_iter; it++) {
for (int i = 0; i < num_keys1; i++) {
for (int j = 0; j < num_keys2; j++) {
int r1 = rnd.Uniform(num_keys1) * 2;
int r2 = rnd.Uniform(num_keys2);
if (if_query_empty_keys) {
r1++;
r2 = num_keys2 * 2 - r2;
}
if (!for_iterator) {
// Query one existing key;
std::string key = MakeKey(r1, r2, through_db);
uint64_t start_time = Now(env, measured_by_nanosecond);
if (!through_db) {
PinnableSlice value;
MergeContext merge_context;
SequenceNumber max_covering_tombstone_seq = 0;
GetContext get_context(ioptions.user_comparator,
ioptions.merge_operator, ioptions.info_log,
ioptions.statistics, GetContext::kNotFound,
Slice(key), &value, nullptr, &merge_context,
true, &max_covering_tombstone_seq, env);
s = table_reader->Get(read_options, key, &get_context, nullptr);
} else {
s = db->Get(read_options, key, &result);
}
hist.Add(Now(env, measured_by_nanosecond) - start_time);
} else {
int r2_len;
if (if_query_empty_keys) {
r2_len = 0;
} else {
r2_len = rnd.Uniform(num_keys2) + 1;
if (r2_len + r2 > num_keys2) {
r2_len = num_keys2 - r2;
}
}
std::string start_key = MakeKey(r1, r2, through_db);
std::string end_key = MakeKey(r1, r2 + r2_len, through_db);
uint64_t total_time = 0;
uint64_t start_time = Now(env, measured_by_nanosecond);
Iterator* iter = nullptr;
InternalIterator* iiter = nullptr;
if (!through_db) {
iiter = table_reader->NewIterator(
read_options, /*prefix_extractor=*/nullptr, /*arena=*/nullptr,
/*skip_filters=*/false, TableReaderCaller::kUncategorized);
} else {
iter = db->NewIterator(read_options);
}
int count = 0;
for (through_db ? iter->Seek(start_key) : iiter->Seek(start_key);
through_db ? iter->Valid() : iiter->Valid();
through_db ? iter->Next() : iiter->Next()) {
if (if_query_empty_keys) {
break;
}
// verify key;
total_time += Now(env, measured_by_nanosecond) - start_time;
assert(Slice(MakeKey(r1, r2 + count, through_db)) ==
(through_db ? iter->key() : iiter->key()));
start_time = Now(env, measured_by_nanosecond);
if (++count >= r2_len) {
break;
}
}
if (count != r2_len) {
fprintf(
stderr, "Iterator cannot iterate expected number of entries. "
"Expected %d but got %d\n", r2_len, count);
assert(false);
}
delete iter;
total_time += Now(env, measured_by_nanosecond) - start_time;
hist.Add(total_time);
}
}
}
}
fprintf(
stderr,
"==================================================="
"====================================================\n"
"InMemoryTableSimpleBenchmark: %20s num_key1: %5d "
"num_key2: %5d %10s\n"
"==================================================="
"===================================================="
"\nHistogram (unit: %s): \n%s",
opts.table_factory->Name(), num_keys1, num_keys2,
for_iterator ? "iterator" : (if_query_empty_keys ? "empty" : "non_empty"),
measured_by_nanosecond ? "nanosecond" : "microsecond",
hist.ToString().c_str());
if (!through_db) {
env->DeleteFile(file_name);
} else {
delete db;
db = nullptr;
DestroyDB(dbname, opts);
}
}
} // namespace
} // namespace rocksdb
DEFINE_bool(query_empty, false, "query non-existing keys instead of existing "
"ones.");
DEFINE_int32(num_keys1, 4096, "number of distinguish prefix of keys");
DEFINE_int32(num_keys2, 512, "number of distinguish keys for each prefix");
DEFINE_int32(iter, 3, "query non-existing keys instead of existing ones");
DEFINE_int32(prefix_len, 16, "Prefix length used for iterators and indexes");
DEFINE_bool(iterator, false, "For test iterator");
DEFINE_bool(through_db, false, "If enable, a DB instance will be created and "
"the query will be against DB. Otherwise, will be directly against "
"a table reader.");
DEFINE_bool(mmap_read, true, "Whether use mmap read");
DEFINE_string(table_factory, "block_based",
"Table factory to use: `block_based` (default), `plain_table` or "
"`cuckoo_hash`.");
DEFINE_string(time_unit, "microsecond",
"The time unit used for measuring performance. User can specify "
"`microsecond` (default) or `nanosecond`");
int main(int argc, char** argv) {
SetUsageMessage(std::string("\nUSAGE:\n") + std::string(argv[0]) +
" [OPTIONS]...");
ParseCommandLineFlags(&argc, &argv, true);
std::shared_ptr<rocksdb::TableFactory> tf;
rocksdb::Options options;
if (FLAGS_prefix_len < 16) {
options.prefix_extractor.reset(rocksdb::NewFixedPrefixTransform(
FLAGS_prefix_len));
}
rocksdb::ReadOptions ro;
rocksdb::EnvOptions env_options;
options.create_if_missing = true;
options.compression = rocksdb::CompressionType::kNoCompression;
if (FLAGS_table_factory == "cuckoo_hash") {
#ifndef ROCKSDB_LITE
options.allow_mmap_reads = FLAGS_mmap_read;
env_options.use_mmap_reads = FLAGS_mmap_read;
rocksdb::CuckooTableOptions table_options;
table_options.hash_table_ratio = 0.75;
tf.reset(rocksdb::NewCuckooTableFactory(table_options));
#else
fprintf(stderr, "Plain table is not supported in lite mode\n");
exit(1);
#endif // ROCKSDB_LITE
} else if (FLAGS_table_factory == "plain_table") {
#ifndef ROCKSDB_LITE
options.allow_mmap_reads = FLAGS_mmap_read;
env_options.use_mmap_reads = FLAGS_mmap_read;
rocksdb::PlainTableOptions plain_table_options;
plain_table_options.user_key_len = 16;
plain_table_options.bloom_bits_per_key = (FLAGS_prefix_len == 16) ? 0 : 8;
plain_table_options.hash_table_ratio = 0.75;
tf.reset(new rocksdb::PlainTableFactory(plain_table_options));
options.prefix_extractor.reset(rocksdb::NewFixedPrefixTransform(
FLAGS_prefix_len));
#else
fprintf(stderr, "Cuckoo table is not supported in lite mode\n");
exit(1);
#endif // ROCKSDB_LITE
} else if (FLAGS_table_factory == "block_based") {
tf.reset(new rocksdb::BlockBasedTableFactory());
} else {
fprintf(stderr, "Invalid table type %s\n", FLAGS_table_factory.c_str());
}
if (tf) {
// if user provides invalid options, just fall back to microsecond.
bool measured_by_nanosecond = FLAGS_time_unit == "nanosecond";
options.table_factory = tf;
rocksdb::TableReaderBenchmark(options, env_options, ro, FLAGS_num_keys1,
FLAGS_num_keys2, FLAGS_iter, FLAGS_prefix_len,
FLAGS_query_empty, FLAGS_iterator,
FLAGS_through_db, measured_by_nanosecond);
} else {
return 1;
}
return 0;
}
#endif // GFLAGS