Query client

The Query client works a bridge between the connection and the query builder to execute the database queries. Also, it exposes the required APIs used by the query builder to direct read queries to the read replica and writes the write replica.

You can access the query client as follows:

import Database from '@ioc:Adonis/Lucid/Database'
// returns client for the default connection
const client = Database.connection()
// returns client for a named connection
const pgClient = Database.connection('pg')

Methods/Properties

Following is the list of methods and properties available on the query client class.

query

Returns an instance of the query builder for a pre-selected database connection.

client.query()

You can also use the from alias to instantiate a new query instance and select the table.

client.from('users')

insertQuery

Returns an instance of the insert query builder for a pre-selected database connection.

client.insertQuery()

You can also use the table alias to instantiate a new query instance and select the table.

client.table('users')

modelQuery

Returns an instance of the model query builder for a given Lucid model.

import User from 'App/Models/User'
const query = client.modelQuery(User)
const user = await query.first()
console.log(user instanceof User) // true

rawQuery

Returns an instance of the raw query builder for a pre-selected database connection.

await client
.rawQuery('select * from users where id = ?', [1])

knexQuery

Returns an instance of the Knex.js query builder for a pre-selected database connection.

client.knexQuery().select('*')

knexRawQuery

Returns an instance of the Knex.js raw query builder for a pre-selected database connection.

client
.knexRawQuery('select * from users where id = ?', [1])

transaction

Creates a new transaction client instance. Transaction client reserves a dedicated database connection right away and hence it is very important to commit or rollback the transactions properly.

const trx = await client.transaction()
await trx.insertQuery().table('users').insert()
await trx.commit()

getAllTables

Returns an array of all the database tables.

const tables = await client.getAllTables()
console.log(tables)

columnsInfo

Returns a key-value pair of columns in a given database table.

const columns = await client.columnsInfo('users')
console.log(columns)

truncate

Truncate a database table. Optionally you can also cascade foreign key references.

await client.truncate('users')
// cascade
await client.truncate('users', true)

getReadClient

Returns Knex.js instance for the read replica. The write client is returned when not using read/write replicas.

const knex = client.getReadClient()

getWriteClient

Returns Knex.js instance for the write replica. An exception is raised when client is instantiated in the read mode.

const knex = client.getWriteClient()

getAdvisoryLock

Calling getAdvisoryLock obtains an advisory lock in PostgreSQL, and MySQL databases.

Advisory locks are used by database migrations to prevent multiple processes from migrating the database at the same time.

await client.getAdvisoryLock('key_name')
// custom timeout
await client.getAdvisoryLock('key_name', 2000)

releaseAdvisoryLock

Release the previously acquired advisory lock

await client.releaseAdvisoryLock('key_name')

raw

Create a raw reference query instance. The queries generated using the raw method can only be used as a reference in other queries and cannot be executed standalone.

await client.from(
client.raw('select ip_address from user_logins')
)

mode

A readonly property to know the mode in which client instance was created. It is always one of the following

console.log(client.mode)

dialect

Reference to the underlying database dialect . Each supported database driver has its own dialect.

console.log(client.dialect.name)

isTransaction

Find if the client is a transaction client. The value is always false for the query client.

client.isTransaction

connectionName

The connection name for which the query client was instantiated

client.connectionName

debug

Set the value to true to enable debugging for queries executed by the query client.

client.debug = true
await client.from('users').select('*')

schema

Returns reference to the schema builder . The client.schema is a getter that returns a new instance every time you access the property

await client.schema.createTable('users', (table) => {
})