Neapolitan Pizza Margherita


    2.0.2 • Public • Published

    pg-extra Build Status NPM version Dependency Status

    Requires Node 7.x+ and pg 7.3+.

    A simple set of extensions and helpers for node-postgres.

    Quick Overview

    • Does not mutate pg module prototypes.

    • extend(require('pg')) creates pg.extra namespace with pg.extra.Pool and pg.extra.Client.

    • Extends pg.extra.Pool with prototype methods many, one, withTransaction, stream.

    • Extends pg.extra.Client with prototype methods many, one.

    • Extends both with .prepared(name).{query,many,one}()

    • The above methods all return promises just like the existing pool.query() and client.query().

    • Configures the client parser to parse postgres ints and numerics into javascript numbers (else SELECT 1::int8 would return a string "1").

    • Exposes sql and _raw template literal helpers for writing queries.

      const uname = 'nisha42'
      const key = 'uname'
      const direction = 'desc'
        SELECT *
        FROM users
        WHERE lower(uname) = lower(${uname})
      `.append(_raw`ORDER BY ${key} ${direction}`)
    • All query methods fail if the query you pass in is not built with the sql or _raw tag. This avoids the issue of accidentally introducing sql injection with template literals. If you want normal template literal behavior (dumb interpolation), you must tag it with _raw.


    npm install --save pg-extra pg

    Usage / Example

    const { extend, sql, _raw } = require('pg-extra')
    const pg = extend(require('pg'))
    const connectionString = 'postgres://user:pass@localhost:5432/my-db'
    const pool = new pg.extra.Pool({ connectionString, ssl: true })
    exports.findUserByUname = async function(uname) {
        SELECT *
        FROM users
        WHERE lower(uname) = lower(${uname})
    exports.listUsersInCities = async function(cities, direction = 'DESC') {
        return pool.many(
        SELECT *
        FROM users
        WHERE city = ANY (${cities})
      `.append(_raw`ORDER BY uname ${direction}`)
    exports.transferBalance = async function(from, to, amount) {
        return pool.withTransaction(async (client) => {
            await client.query(sql`
          UPDATE accounts SET amount = amount - ${amount} WHERE id = ${from}
            await client.query(sql`
          UPDATE accounts SET amount = amount + ${amount} WHERE id = ${to}


    Return a readable stream of query results.

    In this example, we want to stream all of the usernames in the database to the browser.

    • returns Promise<stream.Readable> rather than just stream.Readable.
    • Provide an optional second argument to transform each row.
    const { _raw } = require('pg-extra')
    router.get('/usernames', async (ctx) => {
        const stream = await
            SELECT uname
            FROM users
            ORDER BY uname
            (row) => row.uname
        ctx.body = stream


    • pool.query(sql`string`): Resolves a postgres Result.
    • pool.many(sql`string`): Resolves an array of rows.
    •`string`): Resolves one row or null.
    • client.query(sql`string`): Resolves a postgres Result.
    • client.many(sql`string`): Resolves an array of rows.
    •`string`): Resolves one row or null.
    • {pool,client}.prepared('funcName').query(sql`string`)
    • {pool,client}.prepared('funcName').many(sql`string`)
    • {pool,client}.prepared('funcName').one(sql`string`)
    • {pool,client}._query(sql, [params], [cb]): The original .query() method. Useful when you want to bypass the sql/_raw requirement, like when executing sql files.

    Query template tags

    pg-extra forces you to tag template strings with sql or _raw. You usually use sql.

    sql is a simple helper that translates this:

      SELECT *
      FROM users
      WHERE lower(uname) = lower(${'nisha42'})
        AND faveFood = ANY (${['kibble', 'tuna']})

    into the sql bindings object that node-postgres expects:

      text: `
        SELECT *
        FROM users
        WHERE lower(uname) = lower($1)
          AND faveFood = ANY ($2)
      values: ['nisha42', ['kibble', 'tuna']]

    _raw is how you opt-in to regular string interpolation, made ugly so that it stands out.

    Use .append() to chain on to the query. The argument to .append() must also be tagged with sql or _raw.

    sql`${'foo'} ${'bar'}`.append(_raw`${'baz'}`) // '$1 $2 baz'
    _raw`${'foo'} ${'bar'}`.append(sql`${'baz'}`) // 'foo bar $1'

    .append() mutates the sql statement object, but you can use .clone() to create a deep copy of an existing instance.

    const statement1 = sql`SELECT 100`
    const statement2 = statement1.clone().append(sql`200`)
    statement1.text === 'SELECT 100'
    statement2.text === 'SELECT 100 , 200'

    Optimization: Bindings Reuse

    (Added in v1.0)

    Bindings are reused for equal (===) values.

    For example:

    const bbcode = '[b]hello world[/b]'
        INSERT INTO posts (length, bbcode, html)
        VALUES (char_length(${bbcode}), ${bbcode}, bbcode_to_html(${bbcode}))

    pg-extra sends that query over the wire to Postgres as this:

        text: `
            INSERT INTO posts (length, bbcode, html)
            VALUES (char_length($1), $1, bbcode_to_html($1))
        values: ['[b]hello world[/b]']

    rather than this:

        text: `
            INSERT INTO posts (length, bbcode, html)
            VALUES (char_length($1), $2, bbcode_to_html($3))
        values: ['[b]hello world[/b]', '[b]hello world[/b]', '[b]hello world[/b]']

    Since bbcode === bbcode, pg-extra will reuse the $1 binding instead of creating and broadcasting additional bindings $2 and $3.

    Keep in mind that === equality compares non-primitive objects like arrays by reference, so VALUES (${[1, 2]}, ${[1, 2]}) (i.e. two different arrays) will be sent as two bindings even though they have the same contents.


    Dynamic Queries

    Reply to issue:

    Let's say you want to bulk-insert:

    INSERT INTO users (username)

    ...And you want to be able to use your bulk-insert query whether you're inserting one or one hundred records.

    I recommend using a SQL-generator like knex:

    const knex = require('knex')({ client: 'pg' })
    const { extend, _raw } = require('pg-extra')
    const pg = extend(require('pg'))
    const pool = new pg.extra.Pool({
        connectionString: 'postgres://user:pass@localhost:5432/my-db',
    // `usernames` will look like ['jack', 'jill', 'john']
    exports.insertUsers = function(usernames) {
        const sqlString = knex('users')
            // we want to pass [{ username: 'jack' }, { username: 'john' }, ...]
            // to the .insert() function, which is a mapping of column names
            // to values.
            .insert( => ({ username })))
        return pool.query(_raw`${sqlString}`)

    Note: Or you can circumvent pg-extra entirely with pool._query(string).


    Setup local postgres database with seeded rows that the tests expect:

    $ createdb pg_extra_test
    $ psql -d pg_extra_test -c 'create table bars (n int not null);'
    $ psql -d pg_extra_test -c 'insert into bars (n) values (1), (2), (3);'

    Then run the tests:

    npm test


    • v2.0.0:
      • extend(require('pg')) now creates extended Pool/Client in a pg.extra.{Pool,Client} namespace instead of mutating pg's prototypes.
    • v1.1.0:
      • Added SqlStatement#clone().
    • v1.0.0:
      • Deprecated q and _unsafe.
      • Added bindings reuse optimization.


    • Add withTransaction() to pg.extra.Client.
    • Add stream() to pg.extra.Client.




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