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/*************************************************************************************************
* Example for typical usage of the on-memory STL secondary index
*
* Copyright 2020 Google LLC
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of the License at
* https://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software distributed under the
* License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied. See the License for the specific language governing permissions
* and limitations under the License.
*************************************************************************************************/
#include "tkrzw_cmd_util.h"
#include "tkrzw_dbm_hash.h"
#include "tkrzw_index.h"
#include "tkrzw_str_util.h"
// All symbols of Tkrzw are under the namespace "tkrzw".
using namespace tkrzw;
// Defines an index by the division ID to member employee IDs.
typedef StdIndex<int64_t, int64_t> DivisionIndex;
// Structure for an employee.
// Actually, you should use a serious implementaton like Protocol Buffers.
struct Employee {
int64_t employee_id = 0;
std::string name;
int64_t division_id = 0;
std::string Serialize() const {
return StrCat(employee_id, "\t", name, "\t", division_id);
}
void Deserialize(const std::string_view& serialized) {
const std::vector<std::string> fields = StrSplit(serialized, "\t");
if (fields.size() < 3) {
Die("Deserialize failed");
}
employee_id = StrToInt(fields[0]);
name = fields[1];
division_id = StrToInt(fields[2]);
}
void Print() {
std::cout << "employee_id=" << employee_id << " name=" << name
<< " division_id=" << division_id << std::endl;
}
};
// Loads index records from the main database.
void LoadIndexRecords(DBM* dbm, DivisionIndex* division_index) {
class IndexBuilder : public DBM::RecordProcessor {
public:
explicit IndexBuilder(DivisionIndex* division_index)
: division_index_(division_index) {}
// This is called for each existing record.
std::string_view ProcessFull(std::string_view key, std::string_view value) override {
const int64_t key_num = StrToInt(key);
Employee employee;
employee.Deserialize(value);
division_index_->Add(employee.division_id, key_num);
return NOOP;
}
private:
DivisionIndex* division_index_;
} index_builder(division_index);
dbm->ProcessEach(&index_builder, false).OrDie();
}
// Updates information of an employee.
// If the name is empty, the entry is removed.
void UpdateEmployee(const Employee& employee, DBM* dbm, DivisionIndex* division_index) {
const std::string& primary_key = ToString(employee.employee_id);
class Updater : public DBM::RecordProcessor {
public:
Updater(const Employee& employee, DivisionIndex* division_index)
: employee_(employee), division_index_(division_index) {
}
// This is called if there is an existing record of the key.
std::string_view ProcessFull(std::string_view key, std::string_view value) override {
const int64_t key_num = StrToInt(key);
Employee old_record;
old_record.Deserialize(value);
// Removes an entry for the existing record.
if (old_record.division_id > 0) {
division_index_->Remove(old_record.division_id, key_num);
}
// If the new name is empty, removes the record.
if (employee_.name.empty()) {
return REMOVE;
}
// Adds an entry for the new record.
if (employee_.division_id > 0) {
division_index_->Add(employee_.division_id, key_num);
}
// Updates the record.
new_value_ = employee_.Serialize();
return new_value_;
}
// This is called if there is no existing record of the key.
std::string_view ProcessEmpty(std::string_view key) override {
const int64_t key_num = StrToInt(key);
// If the new name is empty, nothing is done.
if (employee_.name.empty()) {
return NOOP;
}
// Adds an entry for the new record.
if (employee_.division_id > 0) {
division_index_->Add(employee_.division_id, key_num);
}
// Updates the record.
new_value_ = employee_.Serialize();
return new_value_;
}
private:
const Employee& employee_;
DivisionIndex* division_index_;
std::string new_value_;
} updater(employee, division_index);
dbm->Process(primary_key, &updater, true).OrDie();
}
// Main routine.
int main(int argc, char** argv) {
// Creates the database manager.
HashDBM dbm;
// Prepares an index for divisions and their members.
DivisionIndex division_index;
// Opens a new database,
dbm.Open("casket.tkh", true, File::OPEN_TRUNCATE).OrDie();
// After opening the database, indices should be loaded.
// As the database is empty at this point, there's no effect here.
LoadIndexRecords(&dbm, &division_index);
// Registers employee records.
const std::vector<Employee> employees = {
{10001, "Anne", 301}, {10002, "Marilla", 301}, {10003, "Matthew", 301},
{10004, "Diana", 401},
{10005, "Gilbert", 501},
};
for (const Employee& employee : employees) {
UpdateEmployee(employee, &dbm, &division_index);
}
// Closes the database.
dbm.Close().OrDie();
// Opens an existing database,
dbm.Open("casket.tkh", true).OrDie();
// After opening the database, indices should be loaded.
// All existing records are reflected on the index.
LoadIndexRecords(&dbm, &division_index);
// Updates for employees.
const std::vector<Employee> updates = {
{10001, "Anne", 501}, // Anne works with Gilbert.
{10003, "", 0}, // Matthew left the company.
{10006, "Minnie May", 401},
{10007, "Davy", 301}, {10008, "Dora", 301},
};
for (const Employee& employee : updates) {
UpdateEmployee(employee, &dbm, &division_index);
}
// Prints members for each division.
for (const int64_t division_id : {301, 401, 501}) {
std::cout << "-- Division " << division_id << " --" << std::endl;
for (int64_t employee_id : division_index.GetValues(division_id)) {
Employee employee;
employee.Deserialize(dbm.GetSimple(ToString(employee_id)));
employee.Print();
}
}
// Closes the database.
dbm.Close().OrDie();
return 0;
}
// END OF FILE
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