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rocksdb/db/merge_test.cc

254 lines
5.7 KiB

#include <assert.h>
#include <memory>
#include <iostream>
#include "leveldb/cache.h"
#include "leveldb/comparator.h"
#include "leveldb/db.h"
#include "leveldb/env.h"
#include "leveldb/merge_operator.h"
#include "db/dbformat.h"
#include "utilities/merge_operators.h"
#include "util/testharness.h"
using namespace std;
using namespace leveldb;
auto mergeOperator = MergeOperators::CreateUInt64AddOperator();
std::shared_ptr<DB> OpenDb() {
DB* db;
Options options;
options.create_if_missing = true;
options.merge_operator = mergeOperator.get();
Status s = DB::Open(options, test::TmpDir() + "/merge_testdb", &db);
if (!s.ok()) {
cerr << s.ToString() << endl;
assert(false);
}
return std::shared_ptr<DB>(db);
}
// Imagine we are maintaining a set of uint64 counters.
// Each counter has a distinct name. And we would like
// to support four high level operations:
// set, add, get and remove
// This is a quick implementation without a Merge operation.
class Counters {
protected:
std::shared_ptr<DB> db_;
WriteOptions put_option_;
ReadOptions get_option_;
WriteOptions delete_option_;
uint64_t default_;
public:
explicit Counters(std::shared_ptr<DB> db, uint64_t defaultCount = 0)
: db_(db),
put_option_(),
get_option_(),
delete_option_(),
default_(defaultCount) {
assert(db_);
}
virtual ~Counters() {}
// public interface of Counters.
// All four functions return false
// if the underlying level db operation failed.
// mapped to a levedb Put
bool set(const string& key, uint64_t value) {
// just treat the internal rep of int64 as the string
Slice slice((char *)&value, sizeof(value));
auto s = db_->Put(put_option_, key, slice);
if (s.ok()) {
return true;
} else {
cerr << s.ToString() << endl;
return false;
}
}
// mapped to a leveldb Delete
bool remove(const string& key) {
auto s = db_->Delete(delete_option_, key);
if (s.ok()) {
return true;
} else {
cerr << s.ToString() << std::endl;
return false;
}
}
// mapped to a leveldb Get
bool get(const string& key, uint64_t *value) {
string str;
auto s = db_->Get(get_option_, key, &str);
if (s.IsNotFound()) {
// return default value if not found;
*value = default_;
return true;
} else if (s.ok()) {
// deserialization
if (str.size() != sizeof(uint64_t)) {
cerr << "value corruption\n";
return false;
}
*value = DecodeFixed64(&str[0]);
return true;
} else {
cerr << s.ToString() << std::endl;
return false;
}
}
// 'add' is implemented as get -> modify -> set
// An alternative is a single merge operation, see MergeBasedCounters
virtual bool add(const string& key, uint64_t value) {
uint64_t base = default_;
return get(key, &base) && set(key, base + value);
}
// convenience functions for testing
void assert_set(const string& key, uint64_t value) {
assert(set(key, value));
}
void assert_remove(const string& key) {
assert(remove(key));
}
uint64_t assert_get(const string& key) {
uint64_t value = default_;
assert(get(key, &value));
return value;
}
void assert_add(const string& key, uint64_t value) {
assert(add(key, value));
}
};
// Implement 'add' directly with the new Merge operation
class MergeBasedCounters : public Counters {
private:
WriteOptions merge_option_; // for merge
public:
explicit MergeBasedCounters(std::shared_ptr<DB> db, uint64_t defaultCount = 0)
: Counters(db, defaultCount),
merge_option_() {
}
// mapped to a leveldb Merge operation
virtual bool add(const string& key, uint64_t value) override {
char encoded[sizeof(uint64_t)];
EncodeFixed64(encoded, value);
Slice slice(encoded, sizeof(uint64_t));
auto s = db_->Merge(merge_option_, key, slice);
if (s.ok()) {
return true;
} else {
cerr << s.ToString() << endl;
return false;
}
}
};
void dumpDb(DB* db) {
auto it = unique_ptr<Iterator>(db->NewIterator(ReadOptions()));
for (it->SeekToFirst(); it->Valid(); it->Next()) {
uint64_t value = DecodeFixed64(it->value().data());
cout << it->key().ToString() << ": " << value << endl;
}
assert(it->status().ok()); // Check for any errors found during the scan
}
void testCounters(Counters& counters, DB* db, bool test_compaction) {
FlushOptions o;
o.wait = true;
counters.assert_set("a", 1);
if (test_compaction) db->Flush(o);
assert(counters.assert_get("a") == 1);
counters.assert_remove("b");
// defaut value is 0 if non-existent
assert(counters.assert_get("b") == 0);
counters.assert_add("a", 2);
if (test_compaction) db->Flush(o);
// 1+2 = 3
assert(counters.assert_get("a")== 3);
dumpDb(db);
std::cout << "1\n";
// 1+...+49 = ?
uint64_t sum = 0;
for (int i = 1; i < 50; i++) {
counters.assert_add("b", i);
sum += i;
}
assert(counters.assert_get("b") == sum);
std::cout << "2\n";
dumpDb(db);
std::cout << "3\n";
if (test_compaction) {
db->Flush(o);
cout << "Compaction started ...\n";
db->CompactRange(nullptr, nullptr);
cout << "Compaction ended\n";
dumpDb(db);
assert(counters.assert_get("a")== 3);
assert(counters.assert_get("b") == sum);
}
}
int main(int argc, char *argv[]) {
auto db = OpenDb();
{
cout << "Test read-modify-write counters... \n";
Counters counters(db, 0);
testCounters(counters, db.get(), true);
}
bool compact = false;
if (argc > 1) {
compact = true;
cout << "Turn on Compaction\n";
}
{
cout << "Test merge-based counters... \n";
MergeBasedCounters counters(db, 0);
testCounters(counters, db.get(), compact);
}
return 0;
}