🐘 Non-blocking, event-driven Swift client for PostgreSQL.

What's New

PostgresNIO 1.19.1


SPI(ConnectionPool) changes

  • Fixes Crash in ConnectionPoolStateMachine (#438)

Other Changes

  • Update (#434)


Documentation MIT License Continuous Integration Swift 5.7 - 5.9 SSWG Incubation Level: Graduated

🐘 Non-blocking, event-driven Swift client for PostgreSQL built on [SwiftNIO].


  • A PostgresConnection which allows you to connect to, authorize with, query, and retrieve results from a PostgreSQL server
  • An async/await interface that supports backpressure
  • Automatic conversions between Swift primitive types and the Postgres wire format
  • Integrated with the Swift server ecosystem, including use of SwiftLog.
  • Designed to run efficiently on all supported platforms (tested extensively on Linux and Darwin systems)
  • Support for Network.framework when available (e.g. on Apple platforms)
  • Supports running on Unix Domain Sockets

PostgresNIO does not provide a ConnectionPool as of today, but this is a feature high on our list. If you need a ConnectionPool today, please have a look at Vapor's PostgresKit.

API Docs

Check out the PostgresNIO API docs for a detailed look at all of the classes, structs, protocols, and more.

Getting started

Adding the dependency

Add PostgresNIO as dependency to your Package.swift:

  dependencies: [
    .package(url: "", from: "1.14.0"),

Add PostgresNIO to the target you want to use it in:

  targets: [
    .target(name: "MyFancyTarget", dependencies: [
      .product(name: "PostgresNIO", package: "postgres-nio"),

Creating a connection

To create a connection, first create a connection configuration object:

import PostgresNIO

let config = PostgresConnection.Configuration(
  host: "localhost",
  port: 5432,
  username: "my_username",
  password: "my_password",
  database: "my_database",
  tls: .disable

To create a connection we need a Logger, that is used to log connection background events.

import Logging

let logger = Logger(label: "postgres-logger")

Now we can put it together:

import PostgresNIO
import Logging

let logger = Logger(label: "postgres-logger")

let config = PostgresConnection.Configuration(
  host: "localhost",
  port: 5432,
  username: "my_username",
  password: "my_password",
  database: "my_database",
  tls: .disable

let connection = try await PostgresConnection.connect(
  configuration: config,
  id: 1,
  logger: logger

// Close your connection once done
try await connection.close()


Once a connection is established, queries can be sent to the server. This is very straightforward:

let rows = try await connection.query("SELECT id, username, birthday FROM users", logger: logger)

The query will return a PostgresRowSequence, which is an AsyncSequence of PostgresRows. The rows can be iterated one-by-one:

for try await row in rows {
  // do something with the row

Decoding from PostgresRow

However, in most cases it is much easier to request a row's fields as a set of Swift types:

for try await (id, username, birthday) in rows.decode((Int, String, Date).self) {
  // do something with the datatypes.

A type must implement the PostgresDecodable protocol in order to be decoded from a row. PostgresNIO provides default implementations for most of Swift's builtin types, as well as some types provided by Foundation:

  • Bool
  • Bytes, Data, ByteBuffer
  • Date
  • UInt8, Int16, Int32, Int64, Int
  • Float, Double
  • String
  • UUID

Querying with parameters

Sending parameterized queries to the database is also supported (in the coolest way possible):

let id = 1
let username = "fancyuser"
let birthday = Date()
try await connection.query("""
  INSERT INTO users (id, username, birthday) VALUES (\(id), \(username), \(birthday))
  logger: logger

While this looks at first glance like a classic case of SQL injection 😱, PostgresNIO's API ensures that this usage is safe. The first parameter of the query(_:logger:) method is not a plain String, but a PostgresQuery, which implements Swift's ExpressibleByStringInterpolation protocol. PostgresNIO uses the literal parts of the provided string as the SQL query and replaces each interpolated value with a parameter binding. Only values which implement the PostgresEncodable protocol may be interpolated in this way. As with PostgresDecodable, PostgresNIO provides default implementations for most common types.

Some queries do not receive any rows from the server (most often INSERT, UPDATE, and DELETE queries with no RETURNING clause, not to mention most DDL queries). To support this, the query(_:logger:) method is marked @discardableResult, so that the compiler does not issue a warning if the return value is not used.


Please see for details on the security process.


  • Swift Tools 5.7.0
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Last updated: Mon Dec 04 2023 08:35:37 GMT-1000 (Hawaii-Aleutian Standard Time)