There seems to be an issue with the type error regarding the return of the mysql2/promise

Question

There seems to be an issue with the type error regarding the return of the mysql2/promise

As I delve into using the mysql2/promise library with Typescript, I've encountered a puzzling issue regarding the return type of the query method. Despite my best efforts, I can't seem to resolve an error in my code.
Here is a snippet from my code:

import * as mysql from "mysql2/promise";

let mysql_connection: mysql.Connection = await mysql.createConnection({
   //Some options here.
});

let backend_mysql_res: [(mysql.RowDataPacket[][] | mysql.RowDataPacket[] | mysql.OkPacket | mysql.OkPacket[] | mysql.ResultSetHeader), mysql.FieldPacket[]] = await mysql_connection.query(`SELECT * FROM data.table ORDER BY time DESC LIMIT 1`);

//The error occurs at this line. 
console.log(backend_mysql_res[0][0]);

The error message related to backend_mysql_res[0][0] towards the end of the provided code reads as follows:

TS7053: Element implicitly has an 'any' type because expression of type '0' can't be used to index type 'RowDataPacket[] | RowDataPacket[][] | OkPacket | OkPacket[] | ResultSetHeader'.   Property '0' does not exist on type 'RowDataPacket[] | RowDataPacket[][] | OkPacket | OkPacket[] | ResultSetHeader'.

This error message references type '0', but what exactly does type '0' represent? Is it supposed to denote numbers?
I find myself stumped by this problem and unable to come up with a solution.

Can anyone shed light on the correct types associated with the response of the query method within mysql2/promise? Moreover, the extensive type declaration in let backend_mysql_res ... was advised by the IDE. However, I believe it could be streamlined. Is there a way to simplify the code effectively?

I'm fairly new to learning Typescript, so any assistance would be greatly appreciated.
Please lend me your expertise.

typescript mysql2

Answer 1

Answer №1

I have implemented a custom function that can handle single queries effectively. However, I am still in the process of enhancing it to support multiple queries.

To begin with, I created a wrapper for the MySQL connection query in TypeScript as shown below. Suggestions for improvement are welcome.

import {
  createPool
} from "mysql2/promise";
var pool = createPool({
  waitForConnections: true,
  connectionLimit: 10,
  host: process.env.DBHOST,
  port: parseInt(process.env.DBPORT),
  user: process.env.DBUSER,
  password: process.env.DBPASSWORD,
  database: process.env.DB_NAME,
  multipleStatements: true,
  connectTimeout: 30000,
});
export const fireQuery = async <
  T extends RowDataPacket[][] | RowDataPacket[] | OkPacket | OkPacket[] | ResultSetHeader > (QUERY: string, PARAMS: any[] = []): Promise < T extends RowDataPacket[][] | RowDataPacket[] | OkPacket | OkPacket[] | ResultSetHeader ? T : RowDataPacket[][] | RowDataPacket[] | OkPacket | OkPacket[] | ResultSetHeader > => {
    const connection = await pool.getConnection();
    try {
      console.log("starting transaction...", QUERY, PARAMS);
      await connection.beginTransaction();

      console.log("running query...");
      let queryResult = await connection.query <
        T extends |
        OkPacket |
        ResultSetHeader |
        RowDataPacket[] |
        RowDataPacket[][] |
        OkPacket[] ?
        T : OkPacket | ResultSetHeader | RowDataPacket[] | RowDataPacket[][] | OkPacket[] > (QUERY, PARAMS);
      console.log("committing transaction...");
      await connection.commit();
      console.log("transaction committed.");
      return queryResult[0];
    } catch (error) {
      Sentry.captureException(error);
      connection.rollback();
      console.error("an error occurred:", error);
      throw error;
    } finally {
      connection.release();
    }
  };

This code snippet can be utilized as demonstrated below.

For Single query

export interface ISelectQueryInterface extends RowDataPacket {
col1: string;
col2: number;
col3: boolean;
}

const getUserResult = await fireQuery<UserRDataType[]>("select col1, col2, col3 from table where mobileNo = ?", [data.mobileNo])

For handling multiple queries, a workaround is employed by initially specifying the data type as 'any' and then providing the schema tailored to our requirements.

export interface ISelectQueryInterface1 extends RowDataPacket {
    col1: string;
    col2: number;
    col3: boolean;
}
export interface ISelectQueryInterface2 extends RowDataPacket {
    col4: string;
    col5: number;
    col6: boolean;
}
export interface ISelectQueryInterface3 extends RowDataPacket {
    col7: string;
    col8: number;
}
const output: [ISelectQueryInterface1[], ISelectQueryInterface2[], ISelectQueryInterface3[]] = await fireQuery<any>("select col1, col2, col3 from table where mobileNo = ?;select col4, col5, col6 from table where email = ?;select col7, col8 from table;", ["1234567890", "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="ff9e9d9c9bbf98929e9693d19c9092">[email protected]</a>"]);

Answer 2

I have implemented a custom function that can handle single queries effectively. However, I am still in the process of enhancing it to support multiple queries.

To begin with, I created a wrapper for the MySQL connection query in TypeScript as shown below. Suggestions for improvement are welcome.

import {
  createPool
} from "mysql2/promise";
var pool = createPool({
  waitForConnections: true,
  connectionLimit: 10,
  host: process.env.DBHOST,
  port: parseInt(process.env.DBPORT),
  user: process.env.DBUSER,
  password: process.env.DBPASSWORD,
  database: process.env.DB_NAME,
  multipleStatements: true,
  connectTimeout: 30000,
});
export const fireQuery = async <
  T extends RowDataPacket[][] | RowDataPacket[] | OkPacket | OkPacket[] | ResultSetHeader > (QUERY: string, PARAMS: any[] = []): Promise < T extends RowDataPacket[][] | RowDataPacket[] | OkPacket | OkPacket[] | ResultSetHeader ? T : RowDataPacket[][] | RowDataPacket[] | OkPacket | OkPacket[] | ResultSetHeader > => {
    const connection = await pool.getConnection();
    try {
      console.log("starting transaction...", QUERY, PARAMS);
      await connection.beginTransaction();

      console.log("running query...");
      let queryResult = await connection.query <
        T extends |
        OkPacket |
        ResultSetHeader |
        RowDataPacket[] |
        RowDataPacket[][] |
        OkPacket[] ?
        T : OkPacket | ResultSetHeader | RowDataPacket[] | RowDataPacket[][] | OkPacket[] > (QUERY, PARAMS);
      console.log("committing transaction...");
      await connection.commit();
      console.log("transaction committed.");
      return queryResult[0];
    } catch (error) {
      Sentry.captureException(error);
      connection.rollback();
      console.error("an error occurred:", error);
      throw error;
    } finally {
      connection.release();
    }
  };

This code snippet can be utilized as demonstrated below.

For Single query

export interface ISelectQueryInterface extends RowDataPacket {
col1: string;
col2: number;
col3: boolean;
}

const getUserResult = await fireQuery<UserRDataType[]>("select col1, col2, col3 from table where mobileNo = ?", [data.mobileNo])

For handling multiple queries, a workaround is employed by initially specifying the data type as 'any' and then providing the schema tailored to our requirements.

export interface ISelectQueryInterface1 extends RowDataPacket {
    col1: string;
    col2: number;
    col3: boolean;
}
export interface ISelectQueryInterface2 extends RowDataPacket {
    col4: string;
    col5: number;
    col6: boolean;
}
export interface ISelectQueryInterface3 extends RowDataPacket {
    col7: string;
    col8: number;
}
const output: [ISelectQueryInterface1[], ISelectQueryInterface2[], ISelectQueryInterface3[]] = await fireQuery<any>("select col1, col2, col3 from table where mobileNo = ?;select col4, col5, col6 from table where email = ?;select col7, col8 from table;", ["1234567890", "<a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="ff9e9d9c9bbf98929e9693d19c9092">[email protected]</a>"]);

Answer 3

Answer №2

While it may not be the perfect solution, one approach is to utilize the following code snippet:

let backend_mysql_res: any = await mysql_connection.query(`SELECT * FROM data.table ORDER BY time DESC LIMIT 1`);

This will grant you access to the necessary fields. To view the results, execute:

console.log(backend_mysql_res)

It can provide insight into the outcome.

Answer 4

While it may not be the perfect solution, one approach is to utilize the following code snippet:

let backend_mysql_res: any = await mysql_connection.query(`SELECT * FROM data.table ORDER BY time DESC LIMIT 1`);

This will grant you access to the necessary fields. To view the results, execute:

console.log(backend_mysql_res)

It can provide insight into the outcome.

There seems to be an issue with the type error regarding the return of the mysql2/promise

Answer №1

Answer №2

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