The 'postgres' npm package is a modern, high-performance PostgreSQL client for Node.js. It provides a simple and efficient way to interact with PostgreSQL databases, supporting both basic and advanced database operations.
Connecting to a Database
This feature allows you to establish a connection to a PostgreSQL database using a connection string.
const postgres = require('postgres');
const sql = postgres('postgres://username:password@localhost:5432/mydatabase');Executing Queries
You can execute SQL queries using tagged template literals, which helps in preventing SQL injection attacks.
const result = await sql`SELECT * FROM users WHERE id = ${userId}`;Parameterized Queries
This feature allows you to use parameterized queries to safely pass variables into your SQL statements.
const result = await sql`SELECT * FROM users WHERE age > ${age}`;Transactions
You can perform multiple database operations within a transaction to ensure atomicity.
await sql.begin(async sql => {
await sql`INSERT INTO users (name) VALUES (${name})`;
await sql`INSERT INTO profiles (user_id, bio) VALUES (${userId}, ${bio})`;
});Connection Pooling
The package supports connection pooling to manage multiple database connections efficiently.
const sql = postgres({
host: 'localhost',
port: 5432,
username: 'username',
password: 'password',
database: 'mydatabase',
max: 10 // maximum number of connections in the pool
});The 'pg' package is the official PostgreSQL client for Node.js. It is widely used and provides a comprehensive set of features for interacting with PostgreSQL databases. Compared to 'postgres', 'pg' is more mature and has a larger community, but 'postgres' offers a more modern API and better performance in some cases.
The 'knex' package is a SQL query builder for Node.js that supports multiple database engines, including PostgreSQL. It provides a flexible and powerful API for building and executing SQL queries. While 'knex' is more versatile due to its support for various databases, 'postgres' is more specialized and optimized for PostgreSQL.
The 'sequelize' package is a promise-based ORM for Node.js that supports PostgreSQL, MySQL, SQLite, and MSSQL. It provides a higher-level abstraction for database operations, including model definitions and associations. 'sequelize' is more feature-rich and suitable for complex applications, but 'postgres' offers a simpler and more direct approach to interacting with PostgreSQL.
$ npm install postgres
Create your sql database instance
// db.js
import postgres from 'postgres'
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 > ${ age }
`
// users = Result [{ name: "Walter", age: 80 }, { name: 'Murray', age: 68 }, ...]
return users
}
async function insertUser({ name, age }) {
const users = sql`
insert into users
(name, age)
values
(${ name }, ${ age })
returning name, age
`
// users = Result [{ name: "Murray", age: 68 }]
return users
}
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.
await sql`...` -> Result[]Postgres.js utilizes Tagged template functions to process query parameters before interpolation. Using tagged template literals benefits developers by:
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().
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$1in 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.
const columns = ['name', 'age']
sql`
select
${ sql(columns) }
from users
`
// Which results in:
select "name", "age" from users
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.
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)
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
where inValue 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)
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.
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
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
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()
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"
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.
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
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.END
})
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
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.
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.
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])
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
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)
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 ...`
])
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.
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' }))
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 = logicalinpostgresql.confand connect using either a replication or superuser.
CREATE PUBLICATION alltables FOR ALL TABLES
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
)
You can subscribe to specific operations, tables, or even rows with primary keys.
operation : schema . table = primary_keyoperation 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
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 */ )
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.
const sql = postgres('postgres://username:password@host:port/database', {
host : '', // Postgres ip address[s] 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)
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.
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.
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.
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.
By default, connections will not close until .end() is called. However, it may be useful to have them close automatically when:
sql`` instancesECONNRESET 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
})
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.
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 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.
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 } }
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.
import prexit from 'prexit'
prexit(async () => {
await sql.end({ timeout: 5 })
await new Promise(r => server.close(r))
})
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.
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 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.
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 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.
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.
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 X not implemented
Postgres supports many different authentication types. This one is not supported.
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.
write CONNECTION_ENDED host:port
This error is thrown if the user has called sql.end() and performed a query afterward.
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.
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.
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 recommand 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 ou changed. Feel free to open an issue if you have trouble with types.
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:
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.
FAQs
Fastest full featured PostgreSQL client for Node.js
The npm package postgres receives a total of 350,960 weekly downloads. As such, postgres popularity was classified as popular.
We found that postgres demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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