plv8: JavaScript Language

The plv8 extension allows you use JavaScript within Postgres.

Overview#

While Postgres natively runs SQL, it can also run other "procedural languages". plv8 allows you to run JavaScript code - specifically any code that runs on the V8 JavaScript engine.

It can be used for database functions, triggers, queries and more.

Enable the extension#

Go to the Database page in the Dashboard.
Click on Extensions in the sidebar.
Search for "plv8" and enable the extension.

Create `plv8` functions#

Functions written in plv8 are written just like any other PostgreSQL functions, only with the language identifier set to plv8.

create or replace function function_name()
returns void as $$
    // V8 JavaScript
    // code
    // here
$$ language plv8;

You can call plv8 functions like any other Postgres function:

select function_name();

Examples#

Scalar functions#

A scalar function is anything that takes in some user input and returns a single result.

create or replace function hello_world(name text)
returns text as $$

    let output = `Hello, ${name}!`;
    return output;

$$ language plv8;

Executing SQL#

You can execute SQL within plv8 code using the plv8.execute function.

create or replace function update_user(id bigint, first_name text)
returns smallint as $$

    var num_affected = plv8.execute(
        'update profiles set first_name = $1 where id = $2',
        [first_name, id]
    );

    return num_affected;
$$ language plv8;

Set-returning functions#

A set-returning function is anything that returns a full set of results - for example, rows in a table.

create or replace function get_messages()
returns setof messages as $$

    var json_result = plv8.execute(
        'select * from messages'
    );

    return json_result;
$$ language plv8;

select * from get_messages();

Resources#

Official plv8 documentation
plv8 GitHub Repository

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