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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#

  1. Go to the Database page in the Dashboard.
  2. Click on Extensions in the sidebar.
  3. 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.


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

You can call plv8 functions like any other Postgres function:


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select function_name();

Examples#

Scalar functions#

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


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create or replace function hello_world(name text)
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returns text as $$
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let output = `Hello, ${name}!`;
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return output;
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$$ language plv8;

Executing SQL#

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


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

Set-returning functions#

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


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create or replace function get_messages()
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returns setof messages as $$
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var json_result = plv8.execute(
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'select * from messages'
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);
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return json_result;
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$$ language plv8;
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select * from get_messages();

Resources#

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