Contents

• pg_statviz
  • Design Philosophy
  • Installing the extension
    • Red Hat Enterprise Linux (v8.0+) / Fedora (37+)
    • PGXN (PostgreSQL Extension Network)
    • Manual installation
    • Enabling the extension
  • Installing the utility
    • Requirements
  • Usage
  • Scheduling
  • Visualization
    • Specific module usage
    • Example:
    • Produces:
  • Schema
  • Export data

pg_statviz

pg_statviz is a minimalist extension and utility pair for time series analysis and visualization of PostgreSQL internal statistics.

Created for snapshotting PostgreSQL's cumulative and dynamic statistics and performing time series analysis on them. The accompanying utility can produce visualizations for selected time ranges on the stored stats snapshots, enabling the user to track PostgreSQL performance over time and potentially perform tuning or troubleshooting.

Design Philosophy

Designed with the K.I.S.S. and UNIX philosophies in mind, pg_statviz aims to be a modular, minimal and unobtrusive tool that does only what it's meant for: create snapshots of PostgreSQL statistics for visualization and analysis. To this end, a utility is provided for retrieving the stored snapshots and creating with them simple visualizations using Matplotlib.

Installing the extension

Red Hat Enterprise Linux (v8.0+) / Fedora (37+)

1. Configure the PostgreSQL Yum repository for your Linux distribution, as explained here.

2. Use dnf or yum to install the extension for your PostgreSQL version:

   sudo dnf install pg_statviz_extension-<pg_version>
   OR
   sudo yum install pg_statviz_extension-<pg_version>
   

PGXN (PostgreSQL Extension Network)

The extension is available on PGXN.

To install from PGXN, either download the zip file and install manually or use the PGXN Client to install:

pgxn install pg_statviz

Manual installation

To install manually, clone this repository locally:

git clone https://github.com/vyruss/pg_statviz.git 

This will install the extension in the appropriate location for your system ($SHAREDIR/extension):

cd pg_statviz
sudo make install

Enabling the extension

The extension can now be enabled inside the appropriate database like this, e.g. from psql:

\c mydatabase
CREATE EXTENSION pg_statviz;

This will create the needed tables and functions under schema pgstatviz (note the lack of underscore in the schema name).

Installing the utility

The visualization utility can also be installed from PyPi:

pip install pg_statviz

The utility is also available in the PostgreSQL Yum Repository and can be installed using dnf or yum:

sudo dnf install pg_statviz
OR 
sudo yum install pg_statviz

Requirements

Python 3.9+ is required for the visualization utility.

Usage

The extension can be used by superusers, or any user that has pg_monitor role privileges. To take a snapshot, e.g. from psql:

SELECT pgstatviz.snapshot();

NOTICE:  created pg_statviz snapshot
           snapshot
-------------------------------

 2023-01-27 11:04:58.055453+00

(1 row)

Older snapshots and their associated data can be removed using any time expression. For example, to remove data more than 90 days old:

DELETE FROM pgstatviz.snapshots
WHERE snapshot_tstamp < CURRENT_DATE - 90;

Or all snapshots can be removed like this:

SELECT pgstatviz.delete_snapshots();

NOTICE:  truncating table "snapshots"
NOTICE:  truncate cascades to table "conf"
NOTICE:  truncate cascades to table "buf"
NOTICE:  truncate cascades to table "conn"     
NOTICE:  truncate cascades to table "lock"
NOTICE:  truncate cascades to table "wait"                
NOTICE:  truncate cascades to table "wal"
NOTICE:  truncate cascades to table "db"
 delete_snapshots 
------------------

(1 row)

The pg_monitor role can be assigned to any user:

GRANT pg_monitor TO myuser;

Scheduling

Periodic snapshots can be set up with any job scheduler. For example with cron:

crontab -e -u postgres

Inside the postgres user's crontab, add this line to take a snapshot every 15 minutes:

*/15 * * * * psql -c "SELECT pgstatviz.snapshot()" >/dev/null 2>&1

Visualization

The visualization utility can be called like a PostgreSQL command line tool:

pg_statviz --help

usage: pg_statviz [--help] [--version] [-d DBNAME] [-h HOSTNAME] [-p PORT] [-U USERNAME] [-W]
                  [-D FROM TO] [-O OUTPUTDIR]
                  {analyze,buf,cache,checkp,conn,lock,tuple,wait,wal,xact} ...

run all analysis modules

positional arguments:
  {analyze,buf,cache,checkp,conn,tuple,wait,wal,xact}
    analyze             run all analysis modules
    buf                 run buffers written analysis module
    cache               run cache hit ratio analysis module
    checkp              run checkpoint analysis module
    conn                run connection count analysis module
    lock                run locks analysis module
    tuple               run tuple count analysis module
    wait                run wait events analysis module
    wal                 run WAL generation analysis module
    xact                run transaction count analysis module

options:
  --help
  --version             show program's version number and exit
  -d DBNAME, --dbname DBNAME
                        database name to analyze (default: 'myuser')
  -h HOSTNAME, --host HOSTNAME
                        database server host or socket directory (default: '/var/run/postgresql')
  -p PORT, --port PORT  database server port (default: '5432')
  -U USERNAME, --username USERNAME
                        database user name (default: 'myuser')
  -W, --password        force password prompt (should happen automatically) (default: False)
  -D FROM TO, --daterange FROM TO
                        date range to be analyzed in ISO 8601 format e.g. 2023-01-01T00:00
                        2023-01-01T23:59 (default: [])
  -O OUTPUTDIR, --outputdir OUTPUTDIR
                        output directory (default: -)

Specific module usage

pg_statviz conn --help

usage: pg_statviz conn [-h] [-d DBNAME] [--host HOSTNAME] [-p PORT] [-U USERNAME] [-W]
                       [-D FROM TO] [-O OUTPUTDIR] [-u [USERS ...]]

run connection count analysis module

options:
  -h, --help            show this help message and exit
  -d DBNAME, --dbname DBNAME
                        database name to analyze (default: 'myuser')
  --host HOSTNAME       database server host or socket directory (default: '/var/run/postgresql')
  -p PORT, --port PORT  database server port (default: '5432')
  -U USERNAME, --username USERNAME
                        database user name (default: 'myuser')
  -W, --password        force password prompt (should happen automatically) (default: False)
  -D FROM TO, --daterange FROM TO
                        date range to be analyzed in ISO 8601 format e.g. 2023-01-01T00:00
                        2023-01-01T23:59 (default: [])
  -O OUTPUTDIR, --outputdir OUTPUTDIR
                        output directory (default: -)
  -u [USERS ...], --users [USERS ...]
                        user name(s) to plot in analysis (default: [])

Example:

pg_statviz buf --host localhost -d postgres -U postgres -D 2023-01-24T23:00 2023-01-26

Produces:

Schema

The pg_statviz extension stores its data in the following tables:

Table | Description --- | --- pgstatviz.snapshots | Timestamped snapshots pgstatviz.buf | Buffer, checkpointer and background writer data pgstatviz.conf | PostgreSQL server configuration data pgstatviz.conn | Connection data pgstatviz.db | PostgreSQL server and database statistics pgstatviz.lock | Locks data pgstatviz.wait | Wait events data pgstatviz.wal | WAL generation data

Export data

To dump the captured data, e.g. for analysis on a different machine, run:

pg_dump -a -O -t pgstatviz.* > pg_statviz_data.dump

Load it like this on the target database (which should have pg_statviz installed) :

psql -f pg_statviz_data.dump -d <dbname>

Alternatively, pg_statviz internal tables can also be exported to a tab separated values (TSV) file for use by other tools:

psql -c "COPY pgstatviz.conn TO STDOUT CSV HEADER DELIMITER E'\t'" > conn.tsv

These can be loaded into another database like this (provided the tables exist):

psql -c "COPY pgstatviz.conn FROM STDIN CSV HEADER DELIMITER E'\t'" -d <dbname> < conn.tsv