159 lines
8.1 KiB
Markdown
159 lines
8.1 KiB
Markdown
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## What is pg_stat_monitor?
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The **pg_stat_monitor** is a **PostgreSQL Query Performance Monitoring** 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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2. [Installation](#installation)
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3. [Setup](#setup)
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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. [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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| Distribution | Version | Supported |
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| ------------------------|----------------|--------------------|
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| PostgreSQL | Version < 11 | :x: |
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| PostgreSQL | Version 11 | :heavy_check_mark: |
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| PostgreSQL | Version 12 | :heavy_check_mark: |
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| PostgreSQL | Version 13 | :heavy_check_mark: |
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| Percona Distribution | Version < 11 | :x: |
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| Percona Distribution | Version 11 | :heavy_check_mark: |
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| Percona Distribution | Version 12 | :heavy_check_mark: |
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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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### Installing from PGXN
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You can install ``pg_stat_monitor`` from PGXN (PostgreSQL Extensions Network) using the [PGXN client](https://pgxn.github.io/pgxnclient/).
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Use the following command:
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```sh
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pgxn install pg_stat_monitor
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```
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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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```sh
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cd pg_stat_monitor
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make USE_PGXS=1
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make USE_PGXS=1 install
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```
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## Setup
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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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shared_preload_libraries = 'pg_stat_monitor' # (change requires restart)
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#local_preload_libraries = ''
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#session_preload_libraries = ''
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```
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Or you can set it from `psql` terminal using the ``alter system`` command.
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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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```sh
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sudo systemctl restart postgresql-13
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```
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Create the extension using the ``CREATE EXTENSION`` command.
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```sql
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CREATE EXTENSION pg_stat_monitor;
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CREATE EXTENSION
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```
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```sql
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-- Select some of the query information, like client_ip, username and application_name etc.
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postgres=# SELECT application_name, userid AS user_name, datname AS database_name, substr(query,0, 50) AS query, calls, client_ip
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FROM pg_stat_monitor;
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application_name | user_name | database_name | query | calls | client_ip
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------------------+-----------+---------------+---------------------------------------------------+-------+-----------
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psql | vagrant | postgres | SELECT application_name, userid::regrole AS user_ | 1 | 127.0.0.1
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psql | vagrant | postgres | SELECT application_name, userid AS user_name, dat | 3 | 127.0.0.1
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psql | vagrant | postgres | SELECT application_name, userid AS user_name, dat | 1 | 127.0.0.1
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psql | vagrant | postgres | SELECT application_name, userid AS user_name, dat | 8 | 127.0.0.1
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psql | vagrant | postgres | SELECT bucket, substr(query,$1, $2) AS query, cmd | 1 | 127.0.0.1
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(5 rows)
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```
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```sql
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-- Select queries along with elevel, message and sqlcode which have some errors.
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SELECT decode_error_level(elevel) AS elevel, sqlcode, query, message FROM pg_stat_monitor WHERE elevel != 0;
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elevel. | sqlcode | query | message
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--------------------+---------+-------------------------------------------------------------------------------------------+------------------------------------------------
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ERROR | 132 | select count(*) from pgbench_branches | permission denied for table pgbench_branches
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ERROR | 130 | select 1/0; | division by zero
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ERROR | 132 | SELECT decode_elevel(elevel), sqlcode, message from pg_stat_monitor where elevel != 0; | function decode_elevel(integer) does not exist
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ERROR | 132 | drop table if exists pgbench_accounts, pgbench_branches, pgbench_history, pgbench_tellers | must be owner of table pgbench_accounts
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(4 rows)
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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_monitor``, 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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- 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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Portions Copyright © 2018-2020, Percona LLC and/or its affiliates
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Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
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Portions Copyright (c) 1994, The Regents of the University of California
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