I find myself trying to create a postgres database, so I installed postgres and started a server with initdb /usr/local/pgsql/data, then I started that instance with postgres -D /usr/local/pgsql/data now how can I interact with this through node? For example, what would the connectionstring be, or how am I able to find out what it is.
This question is related to
postgresql
node.js
Slonik is an alternative to answers proposed by Kuberchaun and Vitaly.
Slonik implements safe connection handling; you create a connection pool and connection opening/handling is handled for you.
import {
createPool,
sql
} from 'slonik';
const pool = createPool('postgres://user:password@host:port/database');
return pool.connect((connection) => {
// You are now connected to the database.
return connection.query(sql`SELECT foo()`);
})
.then(() => {
// You are no longer connected to the database.
});
postgres://user:password@host:port/database is your connection string (or more canonically a connection URI or DSN).
The benefit of this approach is that your script ensures that you never accidentally leave hanging connections.
Other benefits for using Slonik include:
Just to add a different option - I use Node-DBI to connect to PG, but also due to the ability to talk to MySQL and sqlite. Node-DBI also includes functionality to build a select statement, which is handy for doing dynamic stuff on the fly.
Quick sample (using config information stored in another file):
var DBWrapper = require('node-dbi').DBWrapper;
var config = require('./config');
var dbConnectionConfig = { host:config.db.host, user:config.db.username, password:config.db.password, database:config.db.database };
var dbWrapper = new DBWrapper('pg', dbConnectionConfig);
dbWrapper.connect();
dbWrapper.fetchAll(sql_query, null, function (err, result) {
if (!err) {
console.log("Data came back from the DB.");
} else {
console.log("DB returned an error: %s", err);
}
dbWrapper.close(function (close_err) {
if (close_err) {
console.log("Error while disconnecting: %s", close_err);
}
});
});
config.js:
var config = {
db:{
host:"plop",
database:"musicbrainz",
username:"musicbrainz",
password:"musicbrainz"
},
}
module.exports = config;
We can also use postgresql-easy. It is built on node-postgres and sqlutil. Note: pg_connection.js & your_handler.js are in the same folder. db.js is in the config folder placed.
pg_connection.js
const PgConnection = require('postgresql-easy');
const dbConfig = require('./config/db');
const pg = new PgConnection(dbConfig);
module.exports = pg;
./config/db.js
module.exports = {
database: 'your db',
host: 'your host',
port: 'your port',
user: 'your user',
password: 'your pwd',
}
your_handler.js
const pg_conctn = require('./pg_connection');
pg_conctn.getAll('your table')
.then(res => {
doResponseHandlingstuff();
})
.catch(e => {
doErrorHandlingStuff()
})
Here is an example I used to connect node.js to my Postgres database.
The interface in node.js that I used can be found here https://github.com/brianc/node-postgres
var pg = require('pg');
var conString = "postgres://YourUserName:YourPassword@localhost:5432/YourDatabase";
var client = new pg.Client(conString);
client.connect();
//queries are queued and executed one after another once the connection becomes available
var x = 1000;
while (x > 0) {
client.query("INSERT INTO junk(name, a_number) values('Ted',12)");
client.query("INSERT INTO junk(name, a_number) values($1, $2)", ['John', x]);
x = x - 1;
}
var query = client.query("SELECT * FROM junk");
//fired after last row is emitted
query.on('row', function(row) {
console.log(row);
});
query.on('end', function() {
client.end();
});
//queries can be executed either via text/parameter values passed as individual arguments
//or by passing an options object containing text, (optional) parameter values, and (optional) query name
client.query({
name: 'insert beatle',
text: "INSERT INTO beatles(name, height, birthday) values($1, $2, $3)",
values: ['George', 70, new Date(1946, 02, 14)]
});
//subsequent queries with the same name will be executed without re-parsing the query plan by postgres
client.query({
name: 'insert beatle',
values: ['Paul', 63, new Date(1945, 04, 03)]
});
var query = client.query("SELECT * FROM beatles WHERE name = $1", ['john']);
//can stream row results back 1 at a time
query.on('row', function(row) {
console.log(row);
console.log("Beatle name: %s", row.name); //Beatle name: John
console.log("Beatle birth year: %d", row.birthday.getYear()); //dates are returned as javascript dates
console.log("Beatle height: %d' %d\"", Math.floor(row.height / 12), row.height % 12); //integers are returned as javascript ints
});
//fired after last row is emitted
query.on('end', function() {
client.end();
});
UPDATE:- THE query.on function is now deprecated and hence the above code will not work as intended. As a solution for this look at:- query.on is not a function
One solution can be using pool of clients like the following:
const { Pool } = require('pg');
var config = {
user: 'foo',
database: 'my_db',
password: 'secret',
host: 'localhost',
port: 5432,
max: 10, // max number of clients in the pool
idleTimeoutMillis: 30000
};
const pool = new Pool(config);
pool.on('error', function (err, client) {
console.error('idle client error', err.message, err.stack);
});
pool.query('SELECT $1::int AS number', ['2'], function(err, res) {
if(err) {
return console.error('error running query', err);
}
console.log('number:', res.rows[0].number);
});
You can see more details on this resource.
A modern and simple approach: pg-promise:
const pgp = require('pg-promise')(/* initialization options */);
const cn = {
host: 'localhost', // server name or IP address;
port: 5432,
database: 'myDatabase',
user: 'myUser',
password: 'myPassword'
};
// alternative:
// var cn = 'postgres://username:password@host:port/database';
const db = pgp(cn); // database instance;
// select and return a single user name from id:
db.one('SELECT name FROM users WHERE id = $1', [123])
.then(user => {
console.log(user.name); // print user name;
})
.catch(error => {
console.log(error); // print the error;
});
// alternative - new ES7 syntax with 'await':
// await db.one('SELECT name FROM users WHERE id = $1', [123]);
The connection string is a string of the form:
postgres://[user[:password]@][host][:port][/dbname]
(where the parts in [...] can optionally be included or excluded)
Some examples of valid connection strings include:
postgres://localhost
postgres://localhost:5432
postgres://localhost/mydb
postgres://user@localhost
postgres://user:secret_password@localhost
If you've just started a database on your local machine, the connection string postgres://localhost will typically work, as that uses the default port number, username, and no password. If the database was started with a specific account, you might find you need to use postgres://pg@localhost or postgres://postgres@localhost
If none of these work, and you have installed docker, another option is to run npx @databases/pg-test start. This will start a postgres server in a docker container and then print out the connection string for you. The pg-test databases are only intended for testing though, so you will loose all your data if your computer restarts.
You can connect to the database and issue queries using @databases/pg:
const createPool = require('@databases/pg');
const {sql} = require('@databases/pg');
// If you're using TypeScript or Babel, you can swap
// the two `require` calls for this import statement:
// import createPool, {sql} from '@databases/pg';
// create a "pool" of connections, you can think of this as a single
// connection, the pool is just used behind the scenes to improve
// performance
const db = createPool('postgres://localhost');
// wrap code in an `async` function so we can use `await`
async function run() {
// we can run sql by tagging it as "sql" and then passing it to db.query
await db.query(sql`
CREATE TABLE IF NOT EXISTS beatles (
name TEXT NOT NULL,
height INT NOT NULL,
birthday DATE NOT NULL
);
`);
const beatle = {
name: 'George',
height: 70,
birthday: new Date(1946, 02, 14),
};
// If we need to pass values, we can use ${...} and they will
// be safely & securely escaped for us
await db.query(sql`
INSERT INTO beatles (name, height, birthday)
VALUES (${beatle.name}, ${beatle.height}, ${beatle.birthday});
`);
console.log(
await db.query(sql`SELECT * FROM beatles;`)
);
}
run().catch(ex => {
// It's a good idea to always report errors using
// `console.error` and set the process.exitCode if
// you're calling an async function at the top level
console.error(ex);
process.exitCode = 1;
}).then(() => {
// For this little demonstration, we'll dispose of the
// connection pool when we're done, so that the process
// exists. If you're building a web server/backend API
// you probably never need to call this.
return db.dispose();
});
You can find a more complete guide to querying Postgres using node.js at https://www.atdatabases.org/docs/pg
Source: Stackoverflow.com