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.

Usage#

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.

1create or replace function function_name()
2returns void as $$
3    // V8 JavaScript
4    // code
5    // here
6$$ language plv8;

You can call plv8 functions like any other Postgres function:

1select function_name();

Examples#

Scalar functions#

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

1create or replace function hello_world(name text)
2returns text as $$
3
4    let output = `Hello, ${name}!`;
5    return output;
6
7$$ language plv8;

Executing SQL#

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

1create or replace function update_user(id bigint, first_name text)
2returns smallint as $$
3
4    var num_affected = plv8.execute(
5        'update profiles set first_name = $1 where id = $2',
6        [first_name, id]
7    );
8
9    return num_affected;
10$$ language plv8;

Set-returning functions#

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

1create or replace function get_messages()
2returns setof messages as $$
3
4    var json_result = plv8.execute(
5        'select * from messages'
6    );
7
8    return json_result;
9$$ language plv8;

Resources#

• Official plv8 documentation
• plv8 GitHub Repository