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CONFIG.md

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Options and configuration

neon(...) function

The neon(...) function returns a query function that can be used both as a tagged-template function and as an ordinary function:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL);

// as a tagged-template function
const rowsA = await sql`SELECT * FROM posts WHERE id = ${postId}`;

// as an ordinary function (exactly equivalent)
const rowsB = await sql('SELECT * FROM posts WHERE id = $1', [postId]);

By default, the query function returned by neon(...) returns only the rows resulting from the provided SQL query, and it returns them as an array of objects where the keys are column names. For example:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL);
const rows = await sql`SELECT * FROM posts WHERE id = ${postId}`;
// -> [{ id: 12, title: "My post", ... }]

However, you can customise the return format of the query function using the configuration options fullResults and arrayMode. These options are available both on the neon(...) function and on the query function it returns (but only when the query function is called as an ordinary function, not as a tagged-template function).

arrayMode: boolean

When arrayMode is true, rows are returned as an array of arrays instead of an array of objects:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL, { arrayMode: true });
const rows = await sql`SELECT * FROM posts WHERE id = ${postId}`;
// -> [[12, "My post", ...]]

Or, with the same effect:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL);
const rows = await sql('SELECT * FROM posts WHERE id = $1', [postId], { arrayMode: true });
// -> [[12, "My post", ...]]

fullResults: boolean

When fullResults is true, additional metadata is returned alongside the result rows, which are then found in the rows property of the return value. The metadata matches what would be returned by node-postgres:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL, { fullResults: true });
const results = await sql`SELECT * FROM posts WHERE id = ${postId}`;
/* -> {
  rows: [{ id: 12, title: "My post", ... }],
  fields: [
    { name: "id", dataTypeID: 23, ... },
    { name: "title", dataTypeID: 25, ... },
    ...
  ],
  rowCount: 1,
  rowAsArray: false,
  command: "SELECT"
} 
*/

Or, with the same effect:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL);
const results = await sql('SELECT * FROM posts WHERE id = $1', [postId], { fullResults: true });
// -> { ... same as above ... }

fetchOptions: Record<string, any>

The fetchOptions option can be passed to neon(...), the transaction function, or the query function (if not within a transaction function). This option takes an object that is merged with the options to the fetch call.

For example, to increase the priority of every database fetch request:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL, { fetchOptions: { priority: 'high' } });
const rows = await sql`SELECT * FROM posts WHERE id = ${postId}`;

Or to implement a fetch timeout:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL);
const abortController = new AbortController();
const timeout = setTimeout(() => abortController.abort('timed out'), 10000);
const rows = await sql(
  'SELECT * FROM posts WHERE id = $1', [postId], 
  { fetchOptions: { signal: abortController.signal } }
);  // throws an error if no result received within 10s
clearTimeout(timeout);

transaction(...) function

The transaction(queriesOrFn, options) function is exposed as a property on the query function. It allows multiple queries to be executed within a single, non-interactive transaction.

The first argument to transaction(), queriesOrFn, is either (1) an array of queries or (2) a non-async function that receives a query function as its argument and returns an array of queries.

The array-of-queries case looks like this:

import { neon } from '@neondatabase/serverless';
const sql = neon(process.env.DATABASE_URL);
const showLatestN = 10;

const [posts, tags] = await sql.transaction([
  sql`SELECT * FROM posts ORDER BY posted_at DESC LIMIT ${showLatestN}`,
  sql`SELECT * FROM tags`,
], { 
  isolationLevel: 'RepeatableRead',
  readOnly: true, 
});

Or as an example of the function case:

const [authors, tags] = await neon(process.env.DATABASE_URL)
  .transaction(txn => [
    txn`SELECT * FROM authors`,
    txn`SELECT * FROM tags`,
  ]);

The optional second argument to transaction(), options, has the same keys as the options to the ordinary query function -- arrayMode, fullResults and fetchOptions -- plus three additional keys that concern the transaction configuration. These transaction-related keys are: isolationMode, readOnly and deferrable. They are described below. Defaults for the transaction-related keys can also be set as options to the neon function.

The fetchOptions option cannot be supplied for individual queries inside transaction(), since only a single fetch is performed for the transaction as a whole. The TypeScript types also currently do not allow arrayMode or fullResults options to be supplied for individual queries within transaction() (although this does have the expected effect if the type errors are ignored).

isolationMode

This option selects a Postgres transaction isolation mode. If present, it must be one of: 'ReadUncommitted', 'ReadCommitted', 'RepeatableRead' or 'Serializable'.

readOnly

If true, this option ensures that a READ ONLY transaction is used to execute the queries passed.

deferrable

If true (and if readOnly is also true, and isolationMode is 'Serializable'), this option ensures that a DEFERRABLE transaction is used to execute the queries passed.

neonConfig configuration

In most cases, there are two ways to set configuration options:

  1. Import neonConfig from the package and set global default options on that.
  2. Set options on individual Client instances using their neonConfig property.

For example:

import { Client, neonConfig } from '@neondatabase/serverless';
import ws from 'ws';

// set default option for all clients
neonConfig.webSocketConstructor = ws;

// override the default option on an individual client
const client = new Client(process.env.DATABASE_URL);
client.neonConfig.webSocketConstructor = ws;

A few configuration options can only be set globally, and these are noted as such below.

webSocketConstructor: typeof WebSocket | undefined

Set this parameter if you're using the driver in an environment where the WebSocket global is not defined, such as Node.js, and you need transaction or session support.

For example:

import { neonConfig } from '@neondatabase/serverless';
import ws from 'ws';
neonConfig.webSocketConstructor = ws;

Advanced configuration

If you're using @neondatabase/serverless to connect to a Neon database, you usually won't need to touch the following configuration options. These options are intended for testing, troubleshooting, and supporting access to non-Neon Postgres instances via self-hosted WebSocket proxies.

poolQueryViaFetch: boolean

Experimentally, when poolQueryViaFetch is true and no listeners for the "connect", "acquire", "release" or "remove" events are set on the Pool, queries via Pool.query() will be sent by low-latency HTTP fetch request.

Default: currently false (but may be true in future).

Note: this option can only be set globally, not on an individual Client instance.

fetchEndpoint: string | ((host: string, port: number | string) => string)

Set fetchEndpoint to set the server endpoint to be sent queries via http fetch.

This may be useful for local development (e.g. to set a port that's not the default 443).

Provide either the full endpoint URL, or a function that takes the database host address and port and returns the full endpoint URL (including protocol).

Default: host => 'https://' + host + '/sql'

Note: this option can only be set globally, not on an individual Client instance.

fetchFunction: any

The fetchFunction option allows you to supply an alternative function for making http requests. The function must accept the same arguments as native fetch.

Default: undefined.

Note: this option can only be set globally, not on an individual Client instance.

wsProxy: string | (host: string, port: number | string) => string

If connecting to a non-Neon database, the wsProxy option should point to your WebSocket proxy. It can either be a string, which will have ?address=host:port appended to it, or a function with the signature (host: string, port: number | string) => string. Either way, the protocol must not be included, because this depends on other options. For example, when using the wsproxy proxy, the wsProxy option should look something like this:

// either:
neonConfig.wsProxy = (host, port) => `my-wsproxy.example.com/v1?address=${host}:${port}`
// or (with identical effect):
neonConfig.wsProxy = 'my-wsproxy.example.com/v1';

Default: host => host + '/v2'.

pipelineConnect: "password" | false

To speed up connection times, the driver will pipeline the first three messages to the database (startup, authentication and first query) if pipelineConnect is set to "password". Note that this will only work if you've configured cleartext password authentication for the relevant user and database.

If your connection doesn't support password authentication, set pipelineConnect to false instead.

Default: "password".

coalesceWrites: boolean

When this option is true, multiple network writes generated in a single iteration of the JavaScript run-loop are coalesced into a single WebSocket message. Since node-postgres sends a lot of very short messages, this may reduce TCP/IP overhead.

Default: true.

forceDisablePgSSL: boolean

This option disables TLS encryption in the Postgres protocol (as set via e.g. ?sslmode=require in the connection string). Security is not compromised if used in conjunction with useSecureWebSocket = true.

Default: true.

useSecureWebSocket: boolean

This option switches between secure (the default) and insecure WebSockets.

To use experimental pure-JS encryption, set useSecureWebSocket = false and forceDisablePgSSL = false, and append ?sslmode=verify-full to your database connection string.

Remember that pure-JS encryption is currently experimental and not suitable for use in production.

Default: true.

subtls: any

Only when using experimental pure-JS TLS encryption, you must supply the subtls TLS library to the subtls option like so:

import { neonConfig } from '@neondatabase/serverless';
import * as subtls from 'subtls';
neonConfig.subtls = subtls;

Default: undefined.

rootCerts: string /* PEM format */

Only when using experimental pure-JS TLS encryption, the rootCerts option determines what root (certificate authority) certificates are trusted.

Its value is a string containing zero or more certificates in PEM format.

Default: "" (the empty string).

pipelineTLS: boolean

Only when using experimental pure-JS encryption, the driver will pipeline the SSL request message and TLS Client Hello if pipelineTLS is set to true. Currently, this is only supported by Neon database hosts, and will fail when communicating with an ordinary Postgres or pgbouncer back-end.

Default: false.