Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China.

PostgreSQL on Amazon RDS

Amazon RDS supports DB instances running several versions of PostgreSQL. For a list of available versions, see Available PostgreSQL database versions.

You can create DB instances and DB snapshots, point-in-time restores and backups. DB instances running PostgreSQL support Multi-AZ deployments, read replicas, Provisioned IOPS, and can be created inside a virtual private cloud (VPC). You can also use Secure Socket Layer (SSL) to connect to a DB instance running PostgreSQL.

Before creating a DB instance, make sure to complete the steps in Setting up for Amazon RDS.

You can use any standard SQL client application to run commands for the instance from your client computer. Such applications include pgAdmin, a popular Open Source administration and development tool for PostgreSQL, or psql, a command line utility that is part of a PostgreSQL installation. To deliver a managed service experience, Amazon RDS doesn't provide host access to DB instances. Also, it restricts access to certain system procedures and tables that require advanced privileges. Amazon RDS supports access to databases on a DB instance using any standard SQL client application. Amazon RDS doesn't allow direct host access to a DB instance by using Telnet or Secure Shell (SSH).

Amazon RDS for PostgreSQL is compliant with many industry standards. For example, you can use Amazon RDS for PostgreSQL databases to build HIPAA-compliant applications and to store healthcare-related information. This includes storage for protected health information (PHI) under a completed Business Associate Agreement (BAA) with Amazon. Amazon RDS for PostgreSQL also meets Federal Risk and Authorization Management Program (FedRAMP) security requirements. Amazon RDS for PostgreSQL has received a FedRAMP Joint Authorization Board (JAB) Provisional Authority to Operate (P-ATO) at the FedRAMP HIGH Baseline within the Amazon GovCloud (US) Regions. For more information on supported compliance standards, see Amazon cloud compliance.

To import PostgreSQL data into a DB instance, follow the information in the Importing data into PostgreSQL on Amazon RDS section.

Common management tasks for Amazon RDS for PostgreSQL

The following are the common management tasks you perform with an Amazon RDS for PostgreSQL DB instance, with links to relevant documentation for each task.

Following is a list of other sections in this guide that can help you understand and use important features of RDS for PostgreSQL:

Working with the database preview environment

When you create a DB instance in Amazon RDS, you know that the PostgreSQL version it's based on has been tested and is fully supported by Amazon. The PostgreSQL community releases new versions and new extensions continuously. You can try out new PostgreSQL versions and extensions before they are fully supported. To do that, you can create a new DB instance in the Database Preview Environment.

DB instances in the Database Preview Environment are similar to DB instances in a production environment. However, keep in mind several important factors:

Features not supported in the preview environment

The following features are not available in the preview environment:

Limitations for PostgreSQL DB instances

The following is a list of limitations for RDS for PostgreSQL:

Available PostgreSQL database versions

Amazon RDS supports DB instances running several editions of PostgreSQL. You can specify any currently available PostgreSQL version when creating a new DB instance. You can specify the major version (such as PostgreSQL 10), and any available minor version for the specified major version. If no version is specified, Amazon RDS defaults to an available version, typically the most recent version. If a major version is specified but a minor version is not, Amazon RDS defaults to a recent release of the major version you have specified.

To see a list of available versions, as well as defaults for newly created DB instances, use the describe-db-engine-versions Amazon CLI command. For example, to display the default PostgreSQL engine version, use the following command:

aws rds describe-db-engine-versions --default-only --engine postgres

For details about the PostgreSQL versions that are supported on Amazon RDS, see the Amazon RDS for PostgreSQL Release Notes.

Deprecation of PostgreSQL version 9.6

On March 31, 2022, Amazon RDS plans to deprecate PostgreSQL 9.6 using the following schedule. This extends the previously announced date of January 18, 2022 to April 26, 2022. You should upgrade all your PostgreSQL 9.6 DB instances to PostgreSQL 12 or higher as soon as possible. We recommend that you first upgrade to minor version 9.6.20 or higher and then upgrade directly to PostgreSQL 12 rather than upgrading to an intermediate major version. For more information, see Upgrading the PostgreSQL DB engine for Amazon RDS.

Deprecated versions for Amazon RDS for PostgreSQL

RDS for PostgreSQL 9.5 is deprecated as of March, 2021. For more information about RDS for PostgreSQL 9.5 deprecation, see Upgrading from Amazon RDS for PostgreSQL version 9.5.

To learn more about deprecation policy for RDS for PostgreSQL, see Amazon RDS FAQs. For more information about PostgreSQL versions, see Versioning Policy in the PostgreSQL documentation.

Supported PostgreSQL extension versions

RDS for PostgreSQL supports many PostgreSQL extensions. The PostgreSQL community sometimes refers to these as modules. Extensions expand on the functionality provided by the PostgreSQL engine. You can find a list of extensions supported by Amazon RDS in the default DB parameter group for that PostgreSQL version. You can also see the current extensions list using psql by showing the rds.extensions parameter as in the following example.

SHOW rds.extensions; 

For details about the PostgreSQL extensions that are supported on Amazon RDS, see PostgreSQL extensions supported on Amazon RDS in Amazon RDS for PostgreSQL Release Notes.

Restricting installation of PostgreSQL extensions

You can restrict which extensions can be installed on a PostgreSQL DB instance. To do so, set the rds.allowed_extensions parameter to a string of comma-separated extension names. Only these extensions can then be installed in the PostgreSQL DB instance.

The default string for the rds.allowed_extensions parameter is '*', which means that any extension available for the engine version can be installed. Changing the rds.allowed_extensions parameter does not require a database restart because it's a dynamic parameter.

The PostgreSQL DB instance engine must be one of the following versions for you to use the rds.allowed_extensions parameter:

To see which extension installations are allowed, use the following psql command.

postgres=> SHOW rds.allowed_extensions;
 rds.allowed_extensions
------------------------
 *

If an extension was installed prior to it being left out of the list in the rds.allowed_extensions parameter, the extension can still be used normally, and commands such as ALTER EXTENSION and DROP EXTENSION will continue to work. However, after an extension is restricted, CREATE EXTENSION commands for the restricted extension will fail.

Installation of extension dependencies with CREATE EXTENSION CASCADE are also restricted. The extension and its dependencies must be specified in rds.allowed_extensions. If an extension dependency installation fails, the entire CREATE EXTENSION CASCADE statement will fail.

If an extension is not included with the rds.allowed_extensions parameter, you will see an error such as the following if you try to install it.

ERROR: permission denied to create extension "extension-name" 
HINT: This extension is not specified in "rds.allowed_extensions". 

PostgreSQL trusted extensions

To install most PostgreSQL extensions requires rds_superuser privileges. PostgreSQL 13 introduced trusted extensions, which reduce the need to grant rds_superuser privileges to regular users. With this feature, users can install many extensions if they have the CREATE privilege on the current database instead of requiring the rds_superuser role. For more information, see the SQL CREATE EXTENSION command in the PostgreSQL documentation.

The following lists the extensions that can be installed by a user who has the CREATE privilege on the current database and do not require the rds_superuser role:

Working with PostgreSQL features supported by Amazon RDS for PostgreSQL

Amazon RDS for PostgreSQL supports many of the most common PostgreSQL features and much common functionality. For example, PostgreSQL has an autovacuum feature that performs routine maintenance on the database. This feature is active by default. Although you can turn off this feature, we highly recommend that you keep it on. Understanding this feature and what you can do to make sure it works as it should is a basic task of any DBA. For more information about the autovacuum, see Working with the PostgreSQL autovacuum on Amazon RDS for PostgreSQL. To learn more about other common DBA tasks, Common DBA tasks for Amazon RDS for PostgreSQL.

RDS for PostgreSQL also supports extensions that add important functionality to the DB instance. For example, you can use the PostGIS extension to work with spatial data, or use the pg_cron extension to schedule maintenance from within the instance. For more information about PostgreSQL extensions, see Using PostgreSQL extensions with Amazon RDS for PostgreSQL.

Foreign data wrappers are a specific type of extension designed to let your RDS for PostgreSQL DB instance work with other commercial databases or data types. For more information about foreign data wrappers supported by RDS for PostgreSQL, see Working with the supported foreign data wrappers for Amazon RDS for PostgreSQL.

Following, you can find information about some PostgreSQL features supported by RDS for PostgreSQL.

Custom data types and enumerations with RDS for PostgreSQL

PostgreSQL supports creating custom data types and working with enumerations. For more information about creating and working with enumerations and other data types, see Enumerated types in the PostgreSQL documentation.

The following is an example of creating a type as an enumeration and then inserting values into a table.

CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple');
CREATE TYPE
CREATE TABLE t1 (colors rainbow);
CREATE TABLE
INSERT INTO t1 VALUES ('red'), ( 'orange');
INSERT 0 2
SELECT * from t1;
colors
--------
red
orange
(2 rows)
postgres=> ALTER TYPE rainbow RENAME VALUE 'red' TO 'crimson';
ALTER TYPE
postgres=> SELECT * from t1;
colors
---------
crimson
orange
(2 rows)

Event triggers for RDS for PostgreSQL

All current PostgreSQL versions support event triggers, and so do all available versions of RDS for PostgreSQL. You can use the main user account (default, postgres) to create, modify, rename, and delete event triggers. Event triggers are at the DB instance level, so they can apply to all databases on an instance.

For example, the following code creates an event trigger that prints the current user at the end of every data definition language (DDL) command.

CREATE OR REPLACE FUNCTION raise_notice_func()
    RETURNS event_trigger
    LANGUAGE plpgsql AS
$$
BEGIN
    RAISE NOTICE 'In trigger function: %', current_user;
END;
$$;

CREATE EVENT TRIGGER event_trigger_1 
    ON ddl_command_end
EXECUTE PROCEDURE raise_notice_func();

For more information about PostgreSQL event triggers, see Event triggers in the PostgreSQL documentation.

There are several limitations to using PostgreSQL event triggers on Amazon RDS. These include the following:

Huge pages for RDS for PostgreSQL

Huge pages are a memory management feature that reduces overhead when a DB instance is working with large contiguous chunks of memory, such as that used by shared buffers. This PostgreSQL feature is supported by all currently available RDS for PostgreSQL versions. You allocate huge pages for your application by using calls to mmap or SYSV shared memory. RDS for PostgreSQL supports both 4-KB and 2-MB page sizes.

You can turn huge pages on or off by changing the value of the huge_pages parameter. The feature is turned on by default for all DB instance classes other than micro, small, and medium DB instance classes.

RDS for PostgreSQL uses huge pages based on the available shared memory. If the DB instance can't use huge pages due to shared memory constraints, Amazon RDS prevents the DB instance from starting. In this case, Amazon RDS sets the status of the DB instance to an incompatible parameters state. If this occurs, you can set the huge_pages parameter to off to allow Amazon RDS to start the DB instance.

The shared_buffers parameter is key to setting the shared memory pool that is required for using huge pages. The default value for the shared_buffers parameter uses a database parameters macro. This macro sets a percentage of the total 8 KB pages available for the DB instance's memory. When you use huge pages, those pages are located with the huge pages. Amazon RDS puts a DB instance into an incompatible parameters state if the shared memory parameters are set to require more than 90 percent of the DB instance memory.

To learn more about PostgreSQL memory management, see Resource Consumption in the PostgreSQL documentation.

Performing logical replication for Amazon RDS for PostgreSQL

Starting with version 10.4, Amazon RDS for PostgreSQL supports the publication and subscription SQL syntax that was first introduced in PostgreSQL 10. To learn more, see Logical replication in the PostgreSQL documentation.

Following, you can find information about setting up logical replication for an RDS for PostgreSQL DB instance.

Understanding logical replication and logical decoding

RDS for PostgreSQL supports the streaming of write-ahead log (WAL) changes using PostgreSQL's logical replication slots. It also supports using logical decoding. You can set up logical replication slots on your instance and stream database changes through these slots to a client such as pg_recvlogical. You create logical replication slots at the database level, and they support replication connections to a single database.

The most common clients for PostgreSQL logical replication are Amazon Database Migration Service or a custom-managed host on an Amazon EC2 instance. The logical replication slot has no information about the receiver of the stream. Also, there's no requirement that the target be a replica database. If you set up a logical replication slot and don't read from the slot, data can be written and quickly fill up your DB instance's storage.

You turn on PostgreSQL logical replication and logical decoding for Amazon RDS with a parameter, a replication connection type, and a security role. The client for logical decoding can be any client that can establish a replication connection to a database on a PostgreSQL DB instance.

For more information on PostgreSQL logical decoding, see the PostgreSQL documentation.

Working with logical replication slots

You can use SQL commands to work with logical slots. For example, the following command creates a logical slot named test_slot using the default PostgreSQL output plugin test_decoding.

SELECT * FROM pg_create_logical_replication_slot('test_slot', 'test_decoding');
slot_name    | xlog_position
-----------------+---------------
regression_slot | 0/16B1970
(1 row)

To list logical slots, use the following command.

SELECT * FROM pg_replication_slots;

To drop a logical slot, use the following command.

SELECT pg_drop_replication_slot('test_slot');
pg_drop_replication_slot
-----------------------
(1 row)

For more examples on working with logical replication slots, see Logical decoding examples in the PostgreSQL documentation.

After you create the logical replication slot, you can start streaming. The following example shows how logical decoding is controlled over the streaming replication protocol. This example uses the program pg_recvlogical, which is included in the PostgreSQL distribution. Doing this requires that client authentication is set up to allow replication connections.

pg_recvlogical -d postgres --slot test_slot -U postgres
    --host -instance-name.111122223333.aws-region.rds.amazonaws.com 
    -f -  --start

To see the contents of the pg_replication_origin_status view, query the pg_show_replication_origin_status function.

SELECT * FROM pg_show_replication_origin_status();
local_id | external_id | remote_lsn | local_lsn
----------+-------------+------------+-----------
(0 rows)

RAM disk for the stats_temp_directory

You can use the RDS for PostgreSQL parameter rds.pg_stat_ramdisk_size to specify the system memory allocated to a RAM disk for storing the PostgreSQL stats_temp_directory. The RAM disk parameter is available for all PostgreSQL versions on Amazon RDS.

Under certain workloads, setting this parameter can improve performance and decrease I/O requirements. For more information about the stats_temp_directory, see the PostgreSQL documentation..

To set up a RAM disk for your stats_temp_directory, set the rds.pg_stat_ramdisk_size parameter to an integer literal value in the parameter group used by your DB instance. This parameter denotes MB, so you must use an integer value. Expressions, formulas, and functions aren't valid for the rds.pg_stat_ramdisk_size parameter. Be sure to reboot the DB instance so that the change takes effect. For information about setting parameters, see Working with parameter groups.

For example, the following Amazon CLI command sets the RAM disk parameter to 256 MB.

aws rds modify-db-parameter-group \
    --db-parameter-group-name pg-95-ramdisk-testing \
    --parameters "ParameterName=rds.pg_stat_ramdisk_size, ParameterValue=256, ApplyMethod=pending-reboot"

After you reboot, run the following command to see the status of the stats_temp_directory.

postgres=> SHOW stats_temp_directory;

The command should return the following.

stats_temp_directory
---------------------------
/rdsdbramdisk/pg_stat_tmp
(1 row)

Tablespaces for RDS for PostgreSQL

RDS for PostgreSQL supports tablespaces for compatibility. Because all storage is on a single logical volume, you can't use tablespaces for I/O splitting or isolation. Our benchmarks and experience indicate that a single logical volume is the best setup for most use cases.

To create and use tablespaces with your RDS for PostgreSQL DB instance requires the rds_superuser role. Your RDS for PostgreSQL DB instance's main user account (default name, postgres) is a member of this role. For more information, see Understanding PostgreSQL roles and permissions.

If you specify a file name when you create a tablespace, the path prefix is /rdsdbdata/db/base/tablespace. The following example places tablespace files in /rdsdbdata/db/base/tablespace/data. This example assumes that a dbadmin user (role) exists and that it's been granted the rds_superuser role needed to work with tablespaces.

postgres=> CREATE TABLESPACE act_data
  OWNER dbadmin
  LOCATION '/data';
CREATE TABLESPACE

To learn more about PostgreSQL tablespaces, see Tablespaces in the PostgreSQL documentation.