# Setting up `pg_stat_monitor` - pg_stat_monitor Documentation
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Author: Percona LLC

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# Setting up `pg_stat_monitor`

## Supported platforms

The PostgreSQL YUM repository supports `pg_stat_monitor` for all supported versions for the following platforms:

- Red Hat Enterprise/Rocky/CentOS/Oracle Linux 7 and 8
- Fedora 33 and 34

Find the list of supported platforms for `pg_stat_monitor` within Percona Distribution for PostgreSQL on the Percona Release Lifecycle Overview page.

## Installation guidelines

You can install `pg_stat_monitor` from the following sources:

- Percona repositories,
- PostgreSQL PGDG yum repositories,
- PGXN and
- source code.

### Installing from Percona repositories

To install `pg_stat_monitor` from Percona repositories, you need to use the `percona-release` repository management tool.

1. Install percona-release following the instructions relevant to your operating system
2. Enable Percona repository:

    percona-release setup ppgXX

Replace XX with the desired PostgreSQL version. For example, to install `pg_stat_monitor` for PostgreSQL 13, specify `ppg13`.

1. Install `pg_stat_monitor` package

   - For Debian and Ubuntu:

       apt-get install percona-pg-stat-monitor13

   - For RHEL and CentOS:

       yum install percona-pg-stat-monitor13

### Installing from PostgreSQL `yum` repositories

Install the PostgreSQL repositories following the instructions in the Linux downloads (Red Hat family) chapter in PostgreSQL documentation.

Install `pg_stat_monitor`:

    dnf install -y pg_stat_monitor_<VERSION>

Replace the `VERSION` variable with the PostgreSQL version you are using (e.g. specify `pg_stat_monitor_13` for PostgreSQL 13)

### Installing from PGXN

You can install `pg_stat_monitor` from PGXN (PostgreSQL Extensions Network) using the PGXN client.

Use the following command:

    pgxn install pg_stat_monitor

### Building from source

To build `pg_stat_monitor` from source code, you require the following:

- git
- make
- gcc
- pg_config

You can download the source code of the latest release of `pg_stat_monitor` from the releases page on GitHub or using git:

    git clone git://github.com/Percona/pg_stat_monitor.git

Compile and install the extension

    cd pg_stat_monitor
    make USE_PGXS=1
    make USE_PGXS=1 install

## Setup

You can enable `pg_stat_monitor` when your `postgresql` instance is not running.

`pg_stat_monitor` needs to be loaded at the start time. The extension requires additional shared memory; therefore, add the `pg_stat_monitor` value for the `shared_preload_libraries` parameter and restart the `postgresql` instance.

Use the ALTER SYSTEMcommand from `psql` terminal to modify the `shared_preload_libraries` parameter.

    ALTER SYSTEM SET shared_preload_libraries = 'pg_stat_monitor';

> NOTE: If you’ve added other modules to the `shared_preload_libraries` parameter (for example, `pg_stat_statements`), list all of them separated by commas for the `ALTER SYSTEM` command.

> For PostgreSQL 13 and earlier versions,`pg_stat_monitor` must follow `pg_stat_statements`. For example, `ALTER SYSTEM SET shared_preload_libraries = 'foo, pg_stat_statements, pg_stat_monitor'`.

> In PostgreSQL 14, modules can be specified in any order.

Start or restart the `postgresql` instance to apply the changes.

- On Debian and Ubuntu:

    sudo systemctl restart postgresql.service

- On Red Hat Enterprise Linux and CentOS:

    sudo systemctl restart postgresql-13

Create the extension using the CREATE EXTENSION command. Using this command requires the privileges of a superuser or a database owner. Connect to `psql` as a superuser for a database and run the following command:

    CREATE EXTENSION pg_stat_monitor;

This allows you to see the stats collected by `pg_stat_monitor`.

By default, `pg_stat_monitor` is created for the `postgres` database. To access the statistics from other databases, you need to create the extension for every database.

    -- Select some of the query information, like client_ip, username and application_name etc.

    postgres=# SELECT application_name, userid AS user_name, datname AS database_name, substr(query,0, 50) AS query, calls, client_ip
               FROM pg_stat_monitor;
     application_name | user_name | database_name |                       query                       | calls | client_ip
    ------------------+-----------+---------------+---------------------------------------------------+-------+-----------
     psql             | vagrant   | postgres      | SELECT application_name, userid::regrole AS user_ |     1 | 127.0.0.1
     psql             | vagrant   | postgres      | SELECT application_name, userid AS user_name, dat |     3 | 127.0.0.1
     psql             | vagrant   | postgres      | SELECT application_name, userid AS user_name, dat |     1 | 127.0.0.1
     psql             | vagrant   | postgres      | SELECT application_name, userid AS user_name, dat |     8 | 127.0.0.1
     psql             | vagrant   | postgres      | SELECT bucket, substr(query,$1, $2) AS query, cmd |     1 | 127.0.0.1
    (5 rows)

To learn more about `pg_stat_monitor` features and usage, see User Guide. To view all other data elements provided by `pg_stat_monitor`, please see the `pg_stat_monitor` view reference.

## Configuration

You can find the configuration parameters of the `pg_stat_monitor` extension in the `pg_stat_monitor_settings` view. To change the default configuration, specify new values for the desired parameters using the GUC (Grant Unified Configuration) system. To learn more, refer to the Configuration section of the user guide.

## Remove `pg_stat_monitor`

To uninstall `pg_stat_monitor`, do the following:

1. Disable statistics collection. Establish the `psql` session and run the following command :

       ALTER SYSTEM SET pg_stat_monitor.pgsm_enable = 0;

2. Drop `pg_stat_monitor` extension:

       DROP EXTENSION pg_stat_monitor;

3. Remove `pg_stat_monitor` from the `shared_preload_libraries` configuration parameter:

       ALTER SYSTEM SET shared_preload_libraries = '';

   Important

   If the `shared_preload_libraries` parameter includes other modules, specify them all for the `ALTER SYSTEM SET` command to keep using them.

4. Restart the `postgresql` instance to apply the changes. The following command restarts PostgreSQL 13. Replace the version value with the one you are using.

   - On Debian and Ubuntu:

       sudo systemctl restart postgresql.service

   - On Red Hat Enterprise Linux and CentOS:

       sudo systemctl restart postgresql-13

Last update: 2022-01-19
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