Using Knex with own pg connection pool - node.js

Question

I would like to use knex as a query builder, but my project already handles its own connection pool.
I wish I could to do something like:
const { Client } = require('pg')
const client = new Client()
await client.connect()
const knex = require('knex')({
client: 'pg',
connection: client,
})
Is there any way to provide knex with the pg client object, instead of letting it to manage its own connection pool?

Answer 1

Workaround
I think there is a way to do that, but it can be done only with a specific query. To do that you can use the connection(pool) method that accept a connection pool instance as argument.
In my case I have required knex without passing a connection argument and then when the connection was established I saved the connection instance in my object. Then when I have to use knex as client I passed the connection instance in the query building.
Code example
Here a code example:
const knex = require('knex')({
client: 'pg' // postgreSQL or whatever
});
const poolConnection = await new Client().connect(); // or any other method to create your connection here
// when you have to query your db
const results = await knex('users')
.connection(poolConnection) // here pass the connection
.where({
email: 'test#tester.com'
})
.select('id', 'email', 'createdAt')
.offset(0)
.limit(1)
.first();
Use case with moleculer
As an example, I have used that with moleculer that provides a Database Adapter that use already itself a SQL client, so knex would build an additional connection to my db. After I retrieved the connection in my microservice I've used that inside knex in the same way described above.
"use strict";
const DbService = require("moleculer-db");
const SQLAdapter = require("moleculer-db-adapter-sequelize");
const Sequelize = require("sequelize");
// here requiring knex without an actual connection
const knex = require("knex")({
client: "pg"
});
module.exports = {
name: "users",
// implementing moleculer ORM
mixins: [DbService],
adapter: new SQLAdapter(process.env.POSTGRECONNECTIONSTRING),
model: {
name: "user",
define: {
id: {
type: Sequelize.INTEGER,
primaryKey: true,
autoIncrement: true
},
email: Sequelize.STRING,
password: Sequelize.STRING,
}
},
actions: {
findByIdRaw: {
params: {
id: "number"
},
handler(ctx) {
const { id } = ctx.params;
// use the connection pool instance
return knex("users")
.connection(this.connection)
.where({
id
})
.select("id", "email", "createdAt")
.offset(0)
.limit(1)
.first();
}
}
},
started() {
// getting the connection from the adapter
return this.adapter.db.connectionManager.getConnection()
.then((connection) => {
// saving connection
this.connection = connection;
return Promise.resolve();
});
}
};
Related documentation
Knex.js
Knex.js-connection
Related links
Moleculer
Moleculer ORM

Answer 2

No. Unless you write your own custom dialect and override connection fetching functionality. Writing custom dialect is described here https://github.com/tgriesser/knex/blob/master/CONTRIBUTING.md#i-would-like-to-add-support-for-new-dialect-to-knex-is-it-possible