я перевел почти весь код на sql базу данных вместо того чтобы брать данные с json файла, осталось заменить только функцию search (функция поиска). вот полный код:

const express = require("express");
const fs = require("fs");
const session = require("express-session");
const fileUpload = require("express-fileupload");
const app = express();
const fuzzball = require("fuzzball");
const mysql = require('mysql');

const connection = mysql.createConnection({
  host: 'localhost',
  user: 'music', // замените на свой логин
  password: 'password', // замените на свой пароль
  database: 'music' // замените на свою базу данных
});

connection.connect((err) => {
  if (err) {
    console.error('Ошибка подключения к базе данных: ', err);
  } else {
    console.log('Подключение к базе данных успешно');
  }
});

app.set("view engine", "ejs");
app.use(express.static("public"));

app.use(express.urlencoded({ extended: true }));
app.use(fileUpload());
app.use(session({
  secret: "mysecretkey",
  resave: false,
  saveUninitialized: false
}));

const citiesAndRegions = JSON.parse(fs.readFileSync("./db/russia.json", "utf8"));


//const predefinedGenres = ['Rock', 'Pop', 'Jazz', 'Hip Hop', 'Electronic', 'Blues'];

// Функция для получения последних музыкантов, зарегистрированных музыкантов
function getLastNRegisteredMusicians(N, callback) {
connection.query("SELECT * FROM users ORDER BY id DESC LIMIT ?", [N], (err, result) => {
if (err) {
console.error("Ошибка при получении последних зарегистрированных музыкантов: ", err);
return callback(err);
} else {
return callback(null, result);
}
});
}

function getMusicians(callback) {
  connection.query("SELECT * FROM users", (err, result) => {
    if (err) {
      console.error("Ошибка при получении списка музыкантов: ", err);
      return callback(err);
    } else {
      return callback(null, result);
    }
  });
}

// Функция для получения музыканта по id
function getMusicianById(id, callback) {
  connection.query("SELECT * FROM users WHERE id=?", [id], (err, result) => {
    if (err) {
      console.error("Ошибка при получении музыканта с id ${id}: ", err);
      return typeof callback === 'function' && callback(err);
    } else {
      return typeof callback === 'function' && callback(null, result[0]);
    }
  });
}

function requireLogin(req, res, next) {
  if (req.session.musicianId) {
    next();
  } else {
    res.redirect("/login");
  }
}
//функция поиска
function search(query = '', role = '', city = '', genre = '') {
  const data = fs.readFileSync('./db/musicians.json');
  
  const musicians = JSON.parse(data).musicians.map(musician => {
    return {
      name: musician.name,
      genre: musician.genre,
      originalName: musician.name,
      profileLink: `/profile/${musician.id}`,
      thumbnail: musician.thumbnail,
      soundcloud: musician.soundcloud,
      role: musician.role,
	  city: musician.city
      
    };
  });

  let results = [];

  if (query || role || city || genre) {
    const lowerQuery = query.toLowerCase();
    results = musicians.filter(musician => {
      const nameScore = musician.name.toLowerCase().startsWith(lowerQuery) ? 2 : musician.name.toLowerCase().includes(lowerQuery) ? 1 : 0;
      const genreScore = musician.genre.toLowerCase().startsWith(lowerQuery) ? 2 : musician.genre.toLowerCase().includes(lowerQuery) ? 1 : 0;
      
     return (
    nameScore + genreScore > 0 &&
    (role === "" || musician.role === role) &&
	(city === "" || (musician.city && musician.city.toLowerCase().trim() === city.toLowerCase().trim())) &&
    (genre === "" || musician.genre.toLowerCase() === genre.toLowerCase())
  );

    }).filter((a) => {
  if (role !== '' && a.role.toLowerCase() !== role.toLowerCase()) {
    return false;
  }
  if (city !== '' && a.city.toLowerCase() !== city.toLowerCase()) {
    return false;
  }
  if (genre !== '' && a.genre.toLowerCase() !== genre.toLowerCase()) {
    return false;
  }
  return true;
})
.sort((a, b) => {
  let scoreA = 0;
  let scoreB = 0;

  if (a.name.toLowerCase().includes(query)) {
    scoreA++;
  }
  if (a.genre.toLowerCase().includes(query)) {
    scoreA++;
  }
  if (b.name.toLowerCase().includes(query)) {
    scoreB++;
  }
  if (b.genre.toLowerCase().includes(query)) {
    scoreB++;
  }

  // Sort by score (descending)
  return scoreB - scoreA;
});

    // Remove duplicates
    results = results.filter((result, index, self) =>
      index === self.findIndex(r => (
        r.name === result.name && r.genre === result.genre && r.city === result.city
      ))
    );
  }

  return results;
}

app.use((req, res, next) => {
  if (req.session.musicianId) {
    getMusicianById(req.session.musicianId, (err, musician) => {
      if (err) {
        console.error("Ошибка при получении current user: ", err);
      } else {
        res.locals.musician = musician;
        res.locals.userLoggedIn = true;
        res.locals.username = musician.name;
      }
    });
  } else {
    res.locals.userLoggedIn = false;
  }
  next();
});

app.get("/", (req, res) => {
getLastNRegisteredMusicians(5, (err, lastRegisteredMusicians) => {
if (err) {
console.error("Ошибка при получении последних зарегистрированных музыкантов: ", err);
res.status(500).send("Ошибка получения данных");
} else {
res.render("index", { musicians: lastRegisteredMusicians, query:'',city:'',role:'',genre:'' });
}
});
});

app.get("/autocomplete/cities", async (req, res) => {
const searchString = req.query.term;

connection.query(
"SELECT city FROM users WHERE city LIKE ?",
[searchString + '%'],
(error, results, fields) => {
if (error) {
console.error("Ошибка выполнения запроса: ", error);
res.status(500).send("Ошибка выполнения запроса");
} else {
const cities = results.map(row => row.city);
res.json(cities);
}
}
);
});

app.get("/register", (req, res) => {
  if (req.session.musicianId) {
    const musician = getMusicianById(req.session.musicianId);
    res.redirect("/profile/" + musician.id);
  } else {
	  
	  
	  
    res.render("register", { citiesAndRegions, city:'', query:'',role:'' });
  }
});

app.post("/register", (req, res) => {
if (req.session.musicianId) {
getMusicianById(req.session.musicianId, (err, musician) => {
if (err) {
console.error("Ошибка при получении музыканта: ", err);
} else {
res.redirect("/profile/" + musician.id);
}
});
} else {

// Проверка на уникальность логина
connection.query("SELECT * FROM users WHERE login=?", [req.body.login], (err, result) => {
if (err) {
console.error("Ошибка при проверке логина: ", err);
res.status(500).send("Ошибка при регистрации");
} else {
if (result.length > 0) {
res.render("register", { error: "This login is already taken", citiesAndRegions, city:'', query:'', role:'' });
} else {
const newMusician = {
name: req.body.name,
genre: req.body.genre,
instrument: req.body.instrument,
soundcloud: req.body.soundcloud,
password: req.body.password,
role: req.body.role,
city: req.body.city,
login: req.body.login,
};

if (req.files && req.files.thumbnail) {
const file = req.files.thumbnail;
const filename = "musician_" + file.name;
file.mv("./public/img/" + filename);
newMusician.thumbnail = filename;
}

connection.query("INSERT INTO users SET ?", newMusician, (err, result) => {
if (err) {
console.error("Ошибка при регистрации нового музыканта: ", err);
res.status(500).send("Ошибка регистрации");
} else {
req.session.musicianId = result.insertId;
res.redirect("/profile/" + result.insertId);
}
});
}
}
});
}
});

app.get("/profile/:id", (req, res) => {
getMusicianById(parseInt(req.params.id), (err, musician) => {
if (err) {
console.error("Ошибка при получении музыканта: ", err);
res.status(500).send("Ошибка при получении данных");
} else {
if (musician) {
res.render("profile", { musician: musician, city:'', query:'', role:'' });
} else {
res.status(404).send("Musician not found");
}
}
});
});

app.get("/login", (req, res) => {
  res.render("login");
});

app.post("/login", (req, res) => {
  connection.query("SELECT * FROM users WHERE login=? AND password=?", [req.body.login, req.body.password], (err, result) => {
      if (err) {
        console.error("Ошибка при входе: ", err);
        res.status(500).send("Ошибка при входе");
      } else {
        if (result.length > 0) {
          req.session.musicianId = result[0].id;
          res.redirect("/profile/" + result[0].id);
        } else {
          res.render("login", { error: "Invalid login or password" });
        }
      }
    }
);
});

app.get("/logout", (req, res) => {
  req.session.destroy();
  res.redirect("/");
});

app.get('/search', (req, res) => {
  let query = req.query.query || '';
  const role = req.query.role || '';
  const city = req.query.city || '';
  const genre = req.query.genre || '';

  if (query || role || city || genre) {
    search(query, role, city, genre, (err, musicians) => {
      if (err) {
        res.status(500).send("Ошибка при выполнении поиска");
      } else {
        app.locals.JSON = JSON;
        res.render('search', { musicians, query, role, city, genre, citiesAndRegions});
      }
    });
  } else {
    // Use the getMusicians function instead of reading from musicians.json
    getMusicians((err, musiciansList) => {
      if (err) {
        res.status(500).send("Ошибка при получении списка музыкантов");
      } else {
        const musicians = musiciansList.map(musician => {
          return {
            name: musician.name,
            genre: musician.genre,
            originalName: musician.name,
            profileLink: `/profile/${musician.id}`,
            thumbnail: musician.thumbnail,
            soundcloud: musician.soundcloud,
            role: musician.role,
            city: musician.city
          };
        });

        app.locals.JSON = JSON;
        res.render('search', { musicians, query, role, city, genre, citiesAndRegions});
      }
    });
  }
});


app.get("/profile/:id/edit", requireLogin, (req, res) => {
getMusicianById(parseInt(req.params.id), (err, musician) => {
if (err) {
console.error("Ошибка при получении музыканта: ", err);
res.status(500).send("Ошибка при получении данных");
} else {
if (musician) {
if (req.session.musicianId === musician.id) { // Check if the logged-in user is the owner of the profile
res.render("edit-profile", { musician: musician });
} else {
res.status(403).send("Access denied");
}
} else {
res.status(404).send("Musician not found");
}
}
});
});





app.post("/profile/:id/edit", requireLogin, (req, res) => {
const musicianId = parseInt(req.params.id);
getMusicianById(musicianId, (err, musician) => {
if (err) {
console.error("Ошибка при получении музыканта: ", err);
res.status(500).send("Ошибка при получении данных");
} else {
if (musician) {
const updatedMusician = {
name: req.body.name,
genre: req.body.genre,
instrument: req.body.instrument,
soundcloud: req.body.soundcloud,
soundcloud1: req.body.soundcloud1,
city: req.body.city,
role: req.body.role,
bio: req.body.bio,
};
if (req.files && req.files.thumbnail) {
const file = req.files.thumbnail;
const filename = "musician_" + musicianId + "_" + file.name;
file.mv("./public/img/" + filename);
updatedMusician.thumbnail = filename;
}
connection.query("UPDATE users SET ? WHERE id=?", [updatedMusician, musicianId], (err, result) => {
if (err) {
console.error("Ошибка при обновлении профиля музыканта: ", err);
res.status(500).send("Ошибка при обновлении профиля");
} else {
res.redirect("/profile/" + musicianId);
}
});
} else {
res.status(404).send("Musician not found");
}
}
});
});

function isValidSoundCloudUrl(url) {
  return url.startsWith('https://soundcloud.com/');
}

app.listen(3000, () => {
  console.log("Server started on port 3000");
});