Using PL/Rust to write PostgreSQL functions in the Rust language - Amazon Relational Database Service
Setting up PL/Rust Creating functions with PL/RustUsing crates with PL/RustPL/Rust limitations

Using PL/Rust to write PostgreSQL functions in the Rust language

PL/Rust is a trusted Rust language extension for PostgreSQL. You can use it for stored procedures, functions, and other procedural code that's callable from SQL. The PL/Rust language extension is available in the following versions:

  • RDS for PostgreSQL 16.1 and higher 16 versions

  • RDS for PostgreSQL 15.2-R2 and higher 15 versions

  • RDS for PostgreSQL 14.9 and higher 14 versions

  • RDS for PostgreSQL 13.12 and higher 13 versions

For more information, see PL/Rust on GitHub.

Setting up PL/Rust

To install the plrust extension on your DB instance, add plrust to the shared_preload_libraries parameter in the DB parameter group associated with your DB instance. With the plrust extension installed, you can create functions.

To modify the shared_preload_libraries parameter, your DB instance must be associated with a custom parameter group. For information about creating a custom DB parameter group, see Parameter groups for Amazon RDS.

You can install the plrust extension using the AWS Management Console or the AWS CLI.

The following steps assume that your DB instance is associated with a custom DB parameter group.

Install the plrust extension in the shared_preload_libraries parameter

Complete the following steps using an account that is a member of the rds_superuser group (role).

  1. Sign in to the AWS Management Console and open the Amazon RDS console at https://console.aws.amazon.com/rds/.

  2. In the navigation pane, choose Databases.

  3. Choose the name of your DB instance to display its details.

  4. Open the Configuration tab for your DB instance and find the DB instance parameter group link.

  5. Choose the link to open the custom parameters associated with your DB instance.

  6. In the Parameters search field, type shared_pre to find the shared_preload_libraries parameter.

  7. Choose Edit parameters to access the property values.

  8. Add plrust to the list in the Values field. Use a comma to separate items in the list of values.

  9. Reboot the DB instance so that your change to the shared_preload_libraries parameter takes effect. The initial reboot may require additional time to complete.

  10. When the instance is available, verify that plrust has been initialized. Use psql to connect to the DB instance, and then run the following command.

    SHOW shared_preload_libraries;

    Your output should look similar to the following:

    shared_preload_libraries 
--------------------------
rdsutils,plrust
(1 row)
Install the plrust extension in the shared_preload_libraries parameter

Complete the following steps using an account that is a member of the rds_superuser group (role).

  1. Use the modify-db-parameter-group AWS CLI command to add plrust to the shared_preload_libraries parameter.

    aws rds modify-db-parameter-group \
   --db-parameter-group-name custom-param-group-name \
   --parameters "ParameterName=shared_preload_libraries,ParameterValue=plrust,ApplyMethod=pending-reboot" \
   --region aws-region

  2. Use the reboot-db-instance AWS CLI command to reboot the DB instance and initialize the plrust library. The initial reboot may require additional time to complete.

    aws rds reboot-db-instance \
    --db-instance-identifier your-instance \
    --region aws-region

  3. When the instance is available, you can verify that plrust has been initialized. Use psql to connect to the DB instance, and then run the following command.

    SHOW shared_preload_libraries;

    Your output should look similar to the following:

    shared_preload_libraries
--------------------------
rdsutils,plrust
(1 row)

Creating functions with PL/Rust

PL/Rust will compile the function as a dynamic library, load it, and execute it.

The following Rust function filters multiples out of an array.

postgres=> CREATE LANGUAGE plrust;
CREATE EXTENSION            
CREATE OR REPLACE FUNCTION filter_multiples(a BIGINT[], multiple BIGINT) RETURNS BIGINT[]
    IMMUTABLE STRICT
    LANGUAGE PLRUST AS
$$
    Ok(Some(a.into_iter().filter(|x| x.unwrap() % multiple != 0).collect()))
$$;
        
WITH gen_values AS (
SELECT ARRAY(SELECT * FROM generate_series(1,100)) as arr)
SELECT filter_multiples(arr, 3)
from gen_values;

Using crates with PL/Rust

In RDS for PostgreSQL versions 16.3-R2 and higher, 15.7-R2 and higher 15 versions, 14.12-R2 and higher 14 versions, and 13.15-R2 and higher 13 versions, PL/Rust supports additional crates:

  • url

  • regex

  • serde

  • serde_json

In RDS for PostgreSQL versions 15.5-R2 and higher, 14.10-R2 and higher 14 versions, and 13.13-R2 and higher 13 versions, PL/Rust supports two additional crates:

  • croaring-rs

  • num-bigint

Starting with Amazon RDS for PostgreSQL versions 15.4, 14.9, and 13.12, PL/Rust supports the following crates:

  • aes

  • ctr

  • rand

Only the default features are supported for these crates. New RDS for PostgreSQL versions might contain updated versions of crates, and older versions of crates may no longer be supported.

Follow the best practices for performing a major version upgrade to test whether your PL/Rust functions are compatible with the new major version. For more information, see the blog Best practices for upgrading Amazon RDS to major and minor versions of PostgreSQL and Upgrading the PostgreSQL DB engine for Amazon RDS in the Amazon RDS User Guide.

Examples of using dependencies when creating a PL/Rust function are available at Use dependencies.

PL/Rust limitations

By default, database users can't use PL/Rust. To provide access to PL/Rust, connect as a user with rds_superuser privilege, and run the following command:

postgres=> GRANT USAGE ON LANGUAGE PLRUST TO user;