Fastest full PostgreSQL nodejs client

Getting started


Good UX with Postgres.js

Usage

Create your sql database instance

// db.js
import postgres from 'https://deno.land/x/postgresjs/mod.js'

const sql = postgres({ /* options */ }) // will use psql environment variables

export default sql

Simply import for use elsewhere

// users.js
import sql from './db.js'

async function getUsersOver(age) {
  const users = await sql`
    select
      name,
      age
    from users
    where age > ${ age }
  `
  // users = Result [{ name: "Walter", age: 80 }, { name: 'Murray', age: 68 }, ...]
  return users
}


async function insertUser({ name, age }) {
  const users = await sql`
    insert into users
      (name, age)
    values
      (${ name }, ${ age })
    returning name, age
  `
  // users = Result [{ name: "Murray", age: 68 }]
  return users
}

Table of Contents

Connection

postgres([url], [options])

You can use either a postgres:// url connection string or the options to define your database connection properties. Options in the object will override any present in the url. Options will fall back to the same environment variables as psql.

const sql = postgres('postgres://username:password@host:port/database', {
  host                 : '',            // Postgres ip address[s] or domain name[s]
  port                 : 5432,          // Postgres server port[s]
  database             : '',            // Name of database to connect to
  username             : '',            // Username of database user
  password             : '',            // Password of database user
  ...and more
})

More options can be found in the Connection details section.

Queries

await sql`...` -> Result[]

Postgres.js utilizes Tagged template functions to process query parameters before interpolation. Using tagged template literals benefits developers by:

  1. Enforcing safe query generation
  2. Giving the sql`` function powerful utility and query building features.

Any generic value will be serialized according to an inferred type, and replaced by a PostgreSQL protocol placeholder $1, $2, .... The parameters are then sent separately to the database which handles escaping & casting.

All queries will return a Result array, with objects mapping column names to each row.

const xs = await sql`
  insert into users (
    name, age
  ) values (
    'Murray', 68
  )

  returning *
`

// xs = [{ user_id: 1, name: 'Murray', age: 68 }]

Please note that queries are first executed when awaited – or manually by using .execute().

Query parameters

Parameters are automatically extracted and handled by the database so that SQL injection isn't possible. No special handling is necessary, simply use tagged template literals as usual. Dynamic queries and query building can be seen in the next section. // todo

const name = 'Mur'
    , age = 60

const users = await sql`
  select
    name,
    age
  from users
  where
    name like ${ name + '%' }
    and age > ${ age }
`
// users = [{ name: 'Murray', age: 68 }]

Be careful with quotation marks here. Because Postgres infers column types, you do not need to wrap your interpolated parameters in quotes like '${name}'. This will cause an error because the tagged template replaces ${name} with $1 in the query string, leaving Postgres to do the interpolation. If you wrap that in a string, Postgres will see '$1' and interpret it as a string as opposed to a parameter.

Dynamic column selection

const columns = ['name', 'age']

sql`
  select
    ${ sql(columns) }
  from users
`

// Which results in:
select "name", "age" from users

Dynamic inserts

const user = {
  name: 'Murray',
  age: 68
}

sql`
  insert into users ${
    sql(user, 'name', 'age')
  }
`

// Which results in:
insert into users ("name", "age") values ($1, $2)

You can omit column names and simply execute sql(user) to get all the fields from the object as columns. Be careful not to allow users to supply columns that you do not want to be inserted.

Multiple inserts in one query

If you need to insert multiple rows at the same time it's also much faster to do it with a single insert. Simply pass an array of objects to sql().

const users = [{
  name: 'Murray',
  age: 68,
  garbage: 'ignore'
},
{
  name: 'Walter',
  age: 80
}]

sql`insert into users ${ sql(users, 'name', 'age') }`

// Is translated to:
insert into users ("name", "age") values ($1, $2), ($3, $4)

// Here you can also omit column names which will use object keys as columns
sql`insert into users ${ sql(users) }`

// Which results in:
insert into users ("name", "age") values ($1, $2), ($3, $4)

Dynamic columns in updates

This is also useful for update queries

const user = {
  id: 1,
  name: 'Murray',
  age: 68
}

sql`
  update users set ${
    sql(user, 'name', 'age')
  }
  where user_id = ${ user.id }
`

// Which results in:
update users set "name" = $1, "age" = $2 where user_id = $3

Dynamic values and where in

Value lists can also be created dynamically, making where in queries simple too.

const users = await sql`
  select
    *
  from users
  where age in ${ sql([68, 75, 23]) }
`

or

const [{ a, b, c }] => await sql`
  select
    *
  from (values ${ sql(['a', 'b', 'c']) }) as x(a, b, c)
`

Building queries

Postgres.js features a simple dynamic query builder by conditionally appending/omitting query fragments. It works by nesting sql`` fragments within other sql`` calls or fragments. This allows you to build dynamic queries safely without risking sql injections through usual string concatenation.

Partial queries

const olderThan = x => sql`and age > ${ x }`

const filterAge = true

sql`
  select
   *
  from users
  where name is not null ${
    filterAge
      ? olderThan(50)
      : sql``
  }
`
// Which results in:
select * from users where name is not null
// Or
select * from users where name is not null and age > 50

Dynamic filters

sql`
  select
    *
  from users ${
    id
      ? sql`where user_id = ${ id }`
      : sql``
  }
`

// Which results in:
select * from users
// Or
select * from users where user_id = $1

SQL functions

Using keywords or calling functions dynamically is also possible by using sql`` fragments.

const date = null

sql`
  update users set updated_at = ${ date || sql`now()` }
`

// Which results in:
update users set updated_at = now()

Table names

Dynamic identifiers like table names and column names is also supported like so:

const table = 'users'
    , column = 'id'

sql`
  select ${ sql(column) } from ${ sql(table) }
`

// Which results in:
select "id" from "users"

Advanced query methods

.cursor()

await sql``.cursor([rows = 1], [fn])

Use cursors if you need to throttle the amount of rows being returned from a query. You can use a cursor either as an async iterable or with a callback function. For a callback function new results won't be requested until the promise / async callback function has resolved.

callback function
await sql`
  select
    *
  from generate_series(1,4) as x
`.cursor(async([row]) => {
  // row = { x: 1 }
  await http.request('https://example.com/wat', { row })
}
for await...of
// for await...of
const cursor = sql`select * from generate_series(1,4) as x`.cursor()

for await (const [row] of cursor) {
  // row = { x: 1 }
  await http.request('https://example.com/wat', { row })
}

A single row will be returned by default, but you can also request batches by setting the number of rows desired in each batch as the first argument to .cursor:

await sql`
  select
    *
  from generate_series(1,1000) as x
`.cursor(10, async rows => {
  // rows = [{ x: 1 }, { x: 2 }, ... ]
  await Promise.all(rows.map(row =>
    http.request('https://example.com/wat', { row })
  ))
}

If an error is thrown inside the callback function no more rows will be requested and the outer promise will reject with the thrown error.

You can close the cursor early either by calling break in the for await...of loop, or by returning the token sql.CLOSE from the callback function.

await sql`
  select * from generate_series(1,1000) as x
`.cursor(row => {
  return Math.random() > 0.9 && sql.CLOSE // or sql.END
})

.forEach()

await sql``.forEach(fn)

If you want to handle rows returned by a query one by one, you can use .forEach which returns a promise that resolves once there are no more rows.

await sql`
  select created_at, name from events
`.forEach(row => {
  // row = { created_at: '2019-11-22T14:22:00Z', name: 'connected' }
})

// No more rows

describe

await sql``.describe([rows = 1], fn) -> Result[]

Rather than executing a given query, .describe will return information utilized in the query process. This information can include the query identifier, column types, etc.

This is useful for debugging and analyzing your Postgres queries. Furthermore, .describe will give you access to the final generated query string that would be executed.

Raw

sql``.raw()

Using .raw() will return rows as an array with Buffer values for each column, instead of objects.

This can be useful to receive identically named columns, or for specific performance/transformation reasons. The column definitions are still included on the result array, plus access to parsers for each column.

File

await sql.file(path, [args], [options]) -> Result[]

Using a .sql file for a query is also supported with optional parameters to use if the file includes $1, $2, etc

const result = await sql.file('query.sql', ['Murray', 68])

Canceling Queries in Progress

Postgres.js supports, canceling queries in progress. It works by opening a new connection with a protocol level startup message to cancel the current query running on a specific connection. That means there is no guarantee that the query will be canceled, and due to the possible race conditions it might even result in canceling another query. This is fine for long running queries, but in the case of high load and fast queries it might be better to simply ignore results instead of canceling.

const query = sql`select pg_sleep 100`.execute()
setTimeout(() => query.cancel(), 100)
const result = await query

Unsafe raw string queries

Advanced unsafe use cases

await sql.unsafe(query, [args], [options]) -> Result[]

If you know what you're doing, you can use unsafe to pass any string you'd like to postgres. Please note that this can lead to SQL injection if you're not careful.

sql.unsafe('select ' + danger + ' from users where id = ' + dragons)

Transactions

BEGIN / COMMIT await sql.begin([options = ''], fn) -> fn()

Use sql.begin to start a new transaction. Postgres.js will reserve a connection for the transaction and supply a scoped sql instance for all transaction uses in the callback function. sql.begin will resolve with the returned value from the callback function.

BEGIN is automatically sent with the optional options, and if anything fails ROLLBACK will be called so the connection can be released and execution can continue.

const [user, account] = await sql.begin(async sql => {
  const [user] = await sql`
    insert into users (
      name
    ) values (
      'Murray'
    )
  `

  const [account] = await sql`
    insert into accounts (
      user_id
    ) values (
      ${ user.user_id }
    )
  `

  return [user, account]
})

It's also possible to pipeline the requests in a transaction if needed by returning an array with queries from the callback function like this:

const result = await sql.begin(sql => [
  sql`update ...`,
  sql`update ...`,
  sql`insert ...`
])

SAVEPOINT await sql.savepoint([name], fn) -> fn()

sql.begin('read write', async sql => {
  const [user] = await sql`
    insert into users (
      name
    ) values (
      'Murray'
    )
  `

  const [account] = (await sql.savepoint(sql =>
    sql`
      insert into accounts (
        user_id
      ) values (
        ${ user.user_id }
      )
    `
  ).catch(err => {
    // Account could not be created. ROLLBACK SAVEPOINT is called because we caught the rejection.
  })) || []

  return [user, account]
})
.then(([user, account]) => {
  // great success - COMMIT succeeded
})
.catch(() => {
  // not so good - ROLLBACK was called
})

Do note that you can often achieve the same result using WITH queries (Common Table Expressions) instead of using transactions.

Listen & notify

When you call .listen, a dedicated connection will be created to ensure that you receive notifications in real-time. This connection will be used for any further calls to .listen.

.listen returns a promise which resolves once the LISTEN query to Postgres completes, or if there is already a listener active.

await sql.listen('news', payload => {
  const json = JSON.parse(payload)
  console.log(json.this) // logs 'is'
})

Notify can be done as usual in SQL, or by using the sql.notify method.

sql.notify('news', JSON.stringify({ no: 'this', is: 'news' }))

Realtime subscribe

Postgres.js implements the logical replication protocol of PostgreSQL to support subscription to real-time updates of insert, update and delete operations.

NOTE To make this work you must create the proper publications in your database, enable logical replication by setting wal_level = logical in postgresql.conf and connect using either a replication or superuser.

Quick start

Create a publication (eg. in migration)

CREATE PUBLICATION alltables FOR ALL TABLES

Subscribe to updates

const sql = postgres({ publications: 'alltables' })

const { unsubscribe } = await sql.subscribe('insert:events', (row, { command, relation, key, old }) =>
  // tell about new event row over eg. websockets or do something else
)

Subscribe pattern

You can subscribe to specific operations, tables, or even rows with primary keys.

operation : schema . table = primary_key

operation is one of * | insert | update | delete and defaults to *

schema defaults to public

table is a specific table name and defaults to *

primary_key can be used to only subscribe to specific rows

Examples

sql.subscribe('*',                () => /* everything */ )
sql.subscribe('insert',           () => /* all inserts */ )
sql.subscribe('*:users',          () => /* all operations on the public.users table */ )
sql.subscribe('delete:users',     () => /* all deletes on the public.users table */ )
sql.subscribe('update:users=1',   () => /* all updates on the users row with a primary key = 1 */ )

Numbers, bigint, numeric

Number in javascript is only able to represent 253-1 safely which means that types in PostgreSQLs like bigint and numeric won't fit into Number.

Since Node.js v10.4 we can use BigInt to match the PostgreSQL type bigint which is returned for eg. count(*). Unfortunately, it doesn't work with JSON.stringify out of the box, so Postgres.js will return it as a string.

If you want to use BigInt you can add this custom type:

const sql = postgres({
  types: {
    bigint: postgres.BigInt
  }
})

There is currently no guaranteed way to handle numeric / decimal types in native Javascript. These [and similar] types will be returned as a string. The best way in this case is to use custom types.

Connection details

All Postgres options

const sql = postgres('postgres://username:password@host:port/database', {
  host                 : '',            // Postgres ip address[es] or domain name[s]
  port                 : 5432,          // Postgres server port[s]
  path                 : '',            // unix socket path (usually '/tmp')
  database             : '',            // Name of database to connect to
  username             : '',            // Username of database user
  password             : '',            // Password of database user
  ssl                  : false,         // true, prefer, require, tls.connect options
  max                  : 10,            // Max number of connections
  max_lifetime         : null,          // Max lifetime in seconds (more info below)
  idle_timeout         : 0,             // Idle connection timeout in seconds
  connect_timeout      : 30,            // Connect timeout in seconds
  no_prepare           : false,         // No automatic creation of prepared statements
  types                : [],            // Array of custom types, see more below
  onnotice             : fn,            // Defaults to console.log
  onparameter          : fn,            // (key, value) when server param change
  debug                : fn,            // Is called with (connection, query, params, types)
  transform            : {
    column             : fn,            // Transforms incoming column names
    value              : fn,            // Transforms incoming row values
    row                : fn             // Transforms entire rows
  },
  connection           : {
    application_name   : 'postgres.js', // Default application_name
    ...                                 // Other connection parameters
  },
  target_session_attrs : null,          // Use 'read-write' with multiple hosts to
                                        // ensure only connecting to primary
  fetch_types          : true,          // Automatically fetches types on connect
                                        // on initial connection.
})

Note that max_lifetime = 60 * (30 + Math.random() * 30) by default. This resolves to an interval between 45 and 90 minutes to optimize for the benefits of prepared statements and working nicely with Linux's OOM killer.

SSL

Although vulnerable to MITM attacks, a common configuration for the ssl option for some cloud providers is to set rejectUnauthorized to false (if NODE_ENV is production):

const sql =
  process.env.NODE_ENV === 'production'
    ? // "Unless you're using a Private or Shield Heroku Postgres database, Heroku Postgres does not currently support verifiable certificates"
      // https://help.heroku.com/3DELT3RK/why-can-t-my-third-party-utility-connect-to-heroku-postgres-with-ssl
      postgres({ ssl: { rejectUnauthorized: false } })
    : postgres()

For more information regarding ssl with postgres, check out the Node.js documentation for tls.

Multi-host connections - High Availability (HA)

Multiple connection strings can be passed to postgres() in the form of postgres('postgres://localhost:5432,localhost:5433', ...). This works the same as native the psql command. Read more at multiple host URIs.

Connections will be attempted in order of the specified hosts/ports. On a successful connection, all retries will be reset. This ensures that hosts can come up and down seamlessly.

If you specify target_session_attrs: 'primary' or PGTARGETSESSIONATTRS=primary Postgres.js will only connect to the primary host, allowing for zero downtime failovers.

The Connection Pool

Connections are created lazily once a query is created. This means that simply doing const sql = postgres(...) won't have any effect other than instantiating a new sql instance.

No connection will be made until a query is made.

This means that we get a much simpler story for error handling and reconnections. Queries will be sent over the wire immediately on the next available connection in the pool. Connections are automatically taken out of the pool if you start a transaction using sql.begin(), and automatically returned to the pool once your transaction is done.

Any query which was already sent over the wire will be rejected if the connection is lost. It'll automatically defer to the error handling you have for that query, and since connections are lazy it'll automatically try to reconnect the next time a query is made. The benefit of this is no weird generic "onerror" handler that tries to get things back to normal, and also simpler application code since you don't have to handle errors out of context.

There are no guarantees about queries executing in order unless using a transaction with sql.begin() or setting max: 1. Of course doing a series of queries, one awaiting the other will work as expected, but that's just due to the nature of js async/promise handling, so it's not necessary for this library to be concerned with ordering.

Since this library automatically creates prepared statements, it also has a default max lifetime for connections to prevent memory bloat on the database itself. This is a random interval for each connection between 45 and 90 minutes. This allows multiple connections to come up and down seamlessly without user interference.

Connection timeout

By default, connections will not close until .end() is called. However, it may be useful to have them close automatically when:

  • re-instantiating multiple sql`` instances
  • using Postgres.js in a Serverless environment (Lambda, etc.)
  • using Postgres.js with a database service that automatically closes connections after some time (see ECONNRESET issue)

This can be done using the idle_timeout or max_lifetime options. These configuration options specify the number of seconds to wait before automatically closing an idle connection and the maximum time a connection can exist, respectively.

For example, to close a connection that has either been idle for 20 seconds or existed for more than 30 minutes:

const sql = postgres({
  idle_timeout: 20,
  max_lifetime: 60 * 30
})

Auto fetching of array types

Postgres.js will automatically fetch table/array-type information when it first connects to a database.

If you have revoked access to pg_catalog this feature will no longer work and will need to be disabled.

You can disable this feature by setting fetch_types to false.

Environmental variables

It is also possible to connect to the database without a connection string or any options. Postgres.js will fall back to the common environment variables used by psql as in the table below:

const sql = postgres()
Option Environment Variables
host PGHOST
port PGPORT
database PGDATABASE
username PGUSERNAME or PGUSER
password PGPASSWORD
idle_timeout PGIDLE_TIMEOUT
connect_timeout PGCONNECT_TIMEOUT

Prepared statements

Prepared statements will automatically be created for any queries where it can be inferred that the query is static. This can be disabled by using the no_prepare option. For instance — this is useful when using PGBouncer in transaction mode.

Custom Types

You can add ergonomic support for custom types, or simply use sql.typed(value, type) inline, where type is the PostgreSQL oid for the type and the correctly serialized string. (oid values for types can be found in the pg_catalog.pg_types table.)

Adding Query helpers is the cleanest approach which can be done like this:

const sql = postgres({
  types: {
    rect: {
      // The pg_types oid to pass to the db along with the serialized value.
      to        : 1337,

      // An array of pg_types oids to handle when parsing values coming from the db.
      from      : [1337],

      //Function that transform values before sending them to the db.
      serialize : ({ x, y, width, height }) => [x, y, width, height],

      // Function that transforms values coming from the db.
      parse     : ([x, y, width, height]) => { x, y, width, height }
    }
  }
})

// Now you can use sql.typed.rect() as specified above
const [custom] = sql`
  insert into rectangles (
    name,
    rect
  ) values (
    'wat',
    ${ sql.typed.rect({ x: 13, y: 37, width: 42, height: 80 }) }
  )
  returning *
`

// custom = { name: 'wat', rect: { x: 13, y: 37, width: 42, height: 80 } }

Teardown / Cleanup

To ensure proper teardown and cleanup on server restarts use await sql.end() before process.exit().

Calling sql.end() will reject new queries and return a Promise which resolves when all queries are finished and the underlying connections are closed. If a { timeout } option is provided any pending queries will be rejected once the timeout (in seconds) is reached and the connections will be destroyed.

Sample shutdown using Prexit

import prexit from 'prexit'

prexit(async () => {
  await sql.end({ timeout: 5 })
  await new Promise(r => server.close(r))
})

Error handling

Errors are all thrown to related queries and never globally. Errors coming from database itself are always in the native Postgres format, and the same goes for any Node.js errors eg. coming from the underlying connection.

Query errors will contain a stored error with the origin of the query to aid in tracing errors.

Query errors will also contain the query string and the parameters. These are not enumerable to avoid accidentally leaking confidential information in logs. To log these it is required to specifically access error.query and error.parameters, or set debug: true in options.

There are also the following errors specifically for this library.

UNSAFE_TRANSACTION

Only use sql.begin or max: 1

To ensure statements in a transaction runs on the same connection (which is required for them to run inside the transaction), you must use sql.begin(...) or only allow a single connection in options (max: 1).

UNDEFINED_VALUE

Undefined values are not allowed

Postgres.js won't accept undefined as values in tagged template queries since it becomes ambiguous what to do with the value. If you want to set something to null, use null explicitly.

MESSAGE_NOT_SUPPORTED

X (X) is not supported

Whenever a message is received from Postgres which is not supported by this library. Feel free to file an issue if you think something is missing.

MAX_PARAMETERS_EXCEEDED

Max number of parameters (65534) exceeded

The postgres protocol doesn't allow more than 65534 (16bit) parameters. If you run into this issue there are various workarounds such as using sql([...]) to escape values instead of passing them as parameters.

SASL_SIGNATURE_MISMATCH

Message type X not supported

When using SASL authentication the server responds with a signature at the end of the authentication flow which needs to match the one on the client. This is to avoid man-in-the-middle attacks. If you receive this error the connection was canceled because the server did not reply with the expected signature.

NOT_TAGGED_CALL

Query not called as a tagged template literal

Making queries has to be done using the sql function as a tagged template. This is to ensure parameters are serialized and passed to Postgres as query parameters with correct types and to avoid SQL injection.

AUTH_TYPE_NOT_IMPLEMENTED

Auth type X not implemented

Postgres supports many different authentication types. This one is not supported.

CONNECTION_CLOSED

write CONNECTION_CLOSED host:port

This error is thrown if the connection was closed without an error. This should not happen during normal operations, so please create an issue if this was unexpected.

CONNECTION_ENDED

write CONNECTION_ENDED host:port

This error is thrown if the user has called sql.end() and performed a query afterward.

CONNECTION_DESTROYED

write CONNECTION_DESTROYED host:port

This error is thrown for any queries that were pending when the timeout to sql.end({ timeout: X }) was reached.

CONNECTION_CONNECT_TIMEOUT

write CONNECTION_CONNECT_TIMEOUT host:port

This error is thrown if the startup phase of the connection (tcp, protocol negotiation, and auth) took more than the default 30 seconds or what was specified using connect_timeout or PGCONNECT_TIMEOUT.

TypeScript support

postgres has TypeScript support. You can pass a row list type for your queries in this way:

interface User {
  id: number
  name: string
}

const users = await sql<User[]>`SELECT * FROM users`
users[0].id // ok => number
users[1].name // ok => string
users[0].invalid // fails: `invalid` does not exists on `User`

However, be sure to check the array length to avoid accessing properties of undefined rows:

const users = await sql<User[]>`SELECT * FROM users WHERE id = ${id}`
if (!users.length)
  throw new Error('Not found')
return users[0]

You can also prefer destructuring when you only care about a fixed number of rows. In this case, we recommend you to prefer using tuples to handle undefined properly:

const [user]: [User?] = await sql`SELECT * FROM users WHERE id = ${id}`
if (!user) // => User | undefined
  throw new Error('Not found')
return user // => User

// NOTE:
const [first, second]: [User?] = await sql`SELECT * FROM users WHERE id = ${id}` // fails: `second` does not exist on `[User?]`
const [first, second] = await sql<[User?]>`SELECT * FROM users WHERE id = ${id}` // don't fail : `second: User | undefined`

We do our best to type all the public API, however types are not always updated when features are added or changed. Feel free to open an issue if you have trouble with types.

Migration tools

Postgres.js doesn't come with any migration solution since it's way out of scope, but here are some modules that support Postgres.js for migrations:

Thank you

A really big thank you to @JAForbes who introduced me to Postgres and still holds my hand navigating all the great opportunities we have.

Thanks to @ACXgit for initial tests and dogfooding.

Also thanks to Ryan Dahl for letting me have the postgres npm package name.