PLV8 is a trusted Javascript language extension for PostgreSQL. It can be used for stored procedures, triggers, etc.

PLV8 works with most versions of Postgres, but works best with 9.1 and above, including 10.0, 11, 12, and 13.

Installing PLV8

If the PLV8 extension has been installed to your system, the PLV8 extension can be installed into your PostgreSQL database by running:


Verifying Your Installation

You can verify the installation in two ways. As of PLV8 2.0.0, you can execute a stored procedure:

=# SELECT plv8_version();

Alternately, you can run the following on all versions of PLV8:

=# DO $$ plv8.elog(NOTICE, plv8.version); $$ LANGUAGE plv8;

Updating PLV8

As of PLV8 version 2.3.3, you can use upgrade scripts to upgrade your installation from any version higher than 1.5.0:


Note that until the database has been restarted, the old version of PLV8 will still be loaded, though SELECT plv8_version() will return the new version. This is an artifact of how Postgres manages extensions.

Updating Older PLV8 Installs

Updating PL/v8 is usually straightforward as it is a small and stable extension - it only contains a handful of objects that need to be added to PostgreSQL when installing the extension.

The procedure that is responsible for invoking this installation script (generated during compile time based on plv8.sql.common), is controlled by PostgreSQL and runs when CREATE EXTENSION is executed only. After building, it takes the form of plv8--

When this command is executed, PostgreSQL tracks which objects belong to the extension and conversely removes them upon uninstallation, i.e., whenever DROP EXTENSION is called.

You can explore some of the objects that PL/v8 stores under PostgreSQL:

=# SELECT lanname FROM pg_catalog.pg_language WHERE lanname = 'plv8'; =# SELECT proname FROM pg_proc p WHERE p.proname LIKE 'plv8%'; =# SELECT typname FROM pg_catalog.pg_type WHERE typname LIKE 'plv8%';

To update PostgreSQL, you can DROP the existing extension:


Install the new version, and CREATE the extension:


Alternately, you can backup and restore your database.

Runtime Environment Separation

In PLV8, each session has one global JS runtime context. This enables function invocations at low cost, and sharing common object among the functions. However, for the security reasons, if the user switches to another with SET ROLE command, a new JS runtime context is initialized and used separately. This prevents the risk of unexpected information leaking.

Each plv8 function is invoked as if the function is the property of other object. This means this in each function is a Javascript object that is created every time the function is executed in a query. In other words, the life time and the visibility of this object in a function is only a series of function calls in a query. If you need to share some value among different functions, keep it in the global plv8 object because each function invocation has a different this object.

Start-up Procedure

PLV8 provides a start up facility, which allows you to call a plv8 runtime environment initialization function specified in the GUC variable. This can only be set by someone with administrator access to the database you are accessing.

SET plv8.start_proc = 'plv8_init'; SELECT plv8_test(10);

If this variable is set when the runtime is initialized, before the function call of plv8_test() another plv8 function plv8_init() is invoked. In such initialization function, you can add any properties to plv8 object to expose common values or assign them to the this property. In the initialization function, the receiver this is specially pointing to the global object, so the variables that are assigned to the this property in this initialization are visible from any subsequent function as global variables.

Remember CREATE FUNCTION also starts the plv8 runtime environment, so make sure to SET this GUC before any plv8 actions including CREATE FUNCTION.

Stored procedures

There are a couple of utility procedures that will get installed.

These are useful for long-running connections from various backend services.


Get information about all the current running environments on a specific connection from all users.

Can be run by superuser only.

sql SELECT plv8_info();

Outputs JSON

json [ { "user":"user1", "total_heap_size":1327104, "total_physical_size":474336, "used_heap_size":386680, "heap_size_limit":270008320, "external_memory":0, "number_of_native_contexts":2, "contexts":[] }, { "user":"user2", "total_heap_size":1327104, "total_physical_size":474336, "used_heap_size":386680, "heap_size_limit":270008320, "external_memory":0, "number_of_native_contexts":3, "contexts":["my context"] } ]

Note: "numberof_native_contexts" = "contexts".length + 2_


Reset user isolate or context

To reset a specific context run: sql SELECT plv8_reset('my context');

Will reset the context and re-create globalThis on a next invocation of that context.

To reset all contexts and reboot the whole environment of a specfifc user: sql SELECT plv8_reset();

Superusers can kill a specific user environment by impersonating the user:

sql SET ROLE "some_user"; SELECT plv8_reset(); RESET ROLE;