pg_stat_monitor doc review
Anastasia Alexandrova
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README.md
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README.md
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## What is pg_stat_monitor?
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The pg_stat_monitor is the statistics collection tool based on PostgreSQL's contrib module ``pg_stat_statements``. PostgreSQL’s pg_stat_statements provides the basic statistics, which is sometimes not enough. The major shortcoming in pg_stat_statements is that it accumulates all the queries and their statistics and does not provide aggregated statistics nor histogram information. In this case, a user needs to calculate the aggregate which is quite expensive. ``pg_stat_monitor`` is developed on the basis of pg_stat_statements as its more advanced replacement. It provides all the features of pg_stat_statements plus its own feature set.
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The ``pg_stat_monitor`` is the statistics collection tool based on PostgreSQL's contrib module ``pg_stat_statements``. PostgreSQL’s pg_stat_statements provides the basic statistics, which is sometimes not enough. The major shortcoming in pg_stat_statements is that it accumulates all the queries and their statistics and does not provide aggregated statistics nor histogram information. In this case, a user needs to calculate the aggregate which is quite expensive.
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``pg_stat_monitor`` is developed on the basis of pg_stat_statements as its more advanced replacement. It provides all the features of pg_stat_statements plus its own feature set.
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### How pg_stat_monitor works?
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pg_stat_monitor accumulates the information in the form of buckets. All the aggregated information is bucket based. The size of a bucket and the number of buckets should be configured using GUC (Grand Unified Configuration). When a bucket time elapses, pg_stat_monitor resets all the statistics and switches to the next bucket. After the last bucket elapses, pg_stat_monitor goes back to the first bucket. All the data on the first bucket will vanish; therefore, users must read the buckets before that to not lose the data.
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## Documentation
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1. [Supported PostgreSQL Versions](#supported-postgresql-versions)
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4. [User Guide](https://github.com/percona/pg_stat_monitor/blob/master/docs/USER_GUIDE.md)
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6. [Release Notes](https://github.com/percona/pg_stat_monitor/blob/master/docs/RELEASE_NOTES.md)
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7. [License](https://github.com/percona/pg_stat_monitor/blob/master/LICENSE)
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8. [Copyright Notice](#copyright-notice)
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8. [Submitting Bug Reports](#submitting-bug-reports)
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9. [Copyright Notice](#copyright-notice)
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## Supported PostgreSQL Versions
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The ``pg_stat_monitor`` should work on the latest version of PostgreSQL but is only tested with these PostgreSQL versions:
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| Percona Distribution | Version 13 | :heavy_check_mark: |
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## Installation
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pg_stat_monitor is supplied as part of Percona Distribution for PostgreSQL. The rpm/deb packages are available from Percona repositories. Refer to [Percona Documentation](https://www.percona.com/doc/postgresql/LATEST/installing.html) for installation instructions.
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``pg_stat_monitor`` is supplied as part of Percona Distribution for PostgreSQL. The rpm/deb packages are available from Percona repositories. Refer to [Percona Documentation](https://www.percona.com/doc/postgresql/LATEST/installing.html) for installation instructions.
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The source code of latest release of ``pg_stat_monitor`` can be downloaded from [this GitHub page](https://github.com/Percona/pg_stat_monitor/releases) or it can be downloaded using the git:
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### Installing from source code
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You can download the source code of the latest release of ``pg_stat_monitor`` from [this GitHub page](https://github.com/Percona/pg_stat_monitor/releases) or using git:
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```sh
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git clone git://github.com/Percona/pg_stat_monitor.git
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```
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Compile and Install the extension
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Compile and install the extension
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```sh
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cd pg_stat_monitor
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make USE_PGXS=1
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```
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## Setup
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``pg_stat_monitor`` cannot be installed in your running PostgreSQL instance. It should be set in the ``postgresql.conf`` file.
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``pg_stat_monitor`` cannot be enabled in your running PostgreSQL instance. ``pg_stat_monitor`` needs to be loaded at the start time. This requires adding the ``pg_stat_monitor`` extension for the ``shared_preload_libraries`` parameter and restarting the PostgreSQL instance.
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You can set the ``pg_stat_monitor`` extension in the ``postgresql.conf`` file.
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```
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# - Shared Library Preloading -
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@ -50,9 +61,8 @@ shared_preload_libraries = 'pg_stat_monitor' # (change requires restart)
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#session_preload_libraries = ''
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```
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Or you can do from `psql` terminal using the ``alter system`` command.
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Or you can set it from `psql` terminal using the ``alter system`` command.
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``pg_stat_monitor`` needs to be loaded at the start time. This requires adding the ``pg_stat_monitor`` extension for the ``shared_preload_libraries`` parameter and restart the PostgreSQL instance.
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```sql
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ALTER SYSTEM SET shared_preload_libraries = 'pg_stat_monitor';
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ALTER SYSTEM
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```
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To learn more about ``pg_stat_monitor`` configuration and usage, see [User Guide](https://github.com/percona/pg_stat_monitor/blob/master/docs/USER_GUIDE.md).
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## Submitting Bug Reports
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If you found a bug in ``pg_stat_statements``, please submit the report to the [Jira issue tracker](https://jira.percona.com/projects/PG/issues)
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Start by searching the open tickets for a similar report. If you find that someone else has already reported your issue, then you can upvote that report to increase its visibility.
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If there is no existing report, submit your report following these steps:
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Sign in to [Jira issue tracker](https://jira.percona.com/projects/PG/issues). You will need to create an account if you do not have one.
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In the *Summary*, *Description*, *Steps To Reproduce*, *Affects Version* fields describe the problem you have detected.
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As a general rule of thumb, try to create bug reports that are:
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- Reproducible: describe the steps to reproduce the problem.
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- Specific: include the version of Percona Backup for MongoDB, your environment, and so on.
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- Unique: check if there already exists a JIRA ticket to describe the problem.
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- Scoped to a Single Bug: only report one bug in one JIRA ticket.
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## Copyright Notice
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Copyright (c) 2006 - 2020, Percona LLC.
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## User Guide
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# User Guide
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Create the extension using the ``CREATE EXTENSION`` command.
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This document describes the configuration, key features and usage of ``pg_stat_monitor`` extension and compares it with ``pg_stat_statements``.
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For how to install and set up ``pg_stat_monitor``, see [README](https://github.com/percona/pg_stat_monitor/blob/master/README.md).
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After you've installed and enabled ``pg_stat_monitor``, create the ``pg_stat_monitor`` extension using the ``CREATE EXTENSION`` command.
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```sql
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CREATE EXTENSION pg_stat_monitor;
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```
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Some configuration parameters require the server restart and should be set before the server startup. These must be set in the ``postgresql.conf`` file. Other parameters do not require server restart and can be set permanently either in the ``postgresql.conf`` or from the client (``psql``).
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The table below shows set up options for each configuration parameter and whether the server restart is required to apply its value:
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The table below shows set up options for each configuration parameter and whether the server restart is required to apply the parameter's value:
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| Parameter Name | postgresql.conf | SET | ALTER SYSTEM SET | server restart | configuration reload
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### Usage
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pg_stat_monitor extension contains a view called pg_stat_monitor, which contains all the monitoring information. Following is the list of columns in pg_stat_monitor.
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pg_stat_monitor extension contains a view called pg_stat_monitor, which contains all the monitoring information. Find the list of columns in pg_stat_monitor view in the following table. The table also shows whether a particular column is available in pg_stat_statements.
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| Column | Type | pg_stat_monitor | pg_stat_statments
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| Column | Type | pg_stat_monitor | pg_stat_statements
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|--------------------|--------------------------|----------------------|------------------
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bucket | integer | :heavy_check_mark: | :x:
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bucket_start_time | timestamp with time zone | :heavy_check_mark: | :x:
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cpu_user_time | double precision | :heavy_check_mark: | :x:
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cpu_sys_time | double precision | :heavy_check_mark: | :x:
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Here are some key features of pg_stat_monitor.
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The following are some key features of pg_stat_monitor and usage examples.
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#### Buckets
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pg_stat_monitor collects and aggregates data on a bucket basis. The size of a bucket and the number of buckets should be configured using GUC (Grand Unified Configuration). When a bucket time elapses, pg_stat_monitor resets all the statistics and switches to the next bucket. After the last bucket elapses, pg_stat_monitor goes back to the first bucket. All the data on the first bucket will vanish; therefore, users must read the buckets before that to not lose the data.
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**`bucket`**: Accumulates the statistics per bucket. All the information and aggregate reset for each bucket. The bucket will be a number showing the number of buckets for which this record belongs.
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@ -126,7 +132,7 @@ SELECT bucket, bucket_start_time, query FROM pg_stat_monitor;
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#### Query Information
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**`userid`**: An ID of the user to whom that query belongs. pg_stat_monitor is used to collect queries from all the users; therefore, `userid` is used to segregate the queries based on different users.
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**`userid`**: An ID of the user to whom that query belongs. pg_stat_monitor collects queries from all the users and uses the `userid` to segregate the queries based on different users.
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**`dbid`**: The database ID of the query. pg_stat_monitor accumulates queries from all the databases; therefore, this column is used to identify the database.
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**`calls`**: Number of calls of that particular query.
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##### Example 1: Shows the userid, dbid, unique queryid hash, query, and the total number of calls or that query.
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##### Example 1: Shows the userid, dbid, unique queryid hash, query, and the total number of calls of that query.
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```sql
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SELECT userid, dbid, queryid, substr(query,0, 50) AS query, calls FROM pg_stat_monitor;
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userid | dbid | queryid | query | calls
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(18 rows)
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```
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##### Example 2: Shows the different usernames for the query.
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##### Example 2: Shows different usernames for the query.
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```
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SELECT userid::regrole, datname, substr(query,0, 50) AS query, calls from pg_stat_monitor, pg_database WHERE dbid = oid;
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(5 rows)
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```
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##### Example 3: Shows the different database involved in the queries.
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##### Example 3: Shows the different databases involved in the queries.
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```
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SELECT userid::regrole, datname, substr(query,0, 50) as query, calls from pg_stat_monitor, pg_database WHERE dbid = oid;
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#### Error Messages / Error Codes and Error Level
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**`elevel`**, **`sqlcode`**,**`message`**,: error level / sql code and log/warning/error message
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**`elevel`**, **`sqlcode`**,**`message`**,: error level / sql code and log/warning/ error message
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```sql
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SELECT substr(query,0,50) AS query, decode_error_level(elevel) AS elevel,sqlcode, calls, substr(message,0,50) message
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