Contents

• pg_sessions
• What has been done ?
• How to install
• Configuration
• View and function :
• Future addons :

pg_sessions

Postgresql active session history including pid and timestamp

This project is made because of the lack of admin view on Postgresql

What has been done ?

• based on pg_stat_statement
• added the pid and the last run of the query
• implemented the system statistics based on pg_proctab extension

How to install

Required version : Postgresql 9.5

This is not working on lower versions

Simply fetch the repository

And as root :

export PATH=$PATH:/usr/pgsql/bin
make
make install

Configuration

in the postgresql.conf

shared_preload_libraries = 'pg_sessions'
pg_sessions.max = 5000 # Number of rows to keep in memory
pg_sessions.track = all # Type of statement to keep (none, top, all)
pg_sessions.track_utility = true # Track all utility statements (CREATE, FUNCTIONS...)
pg_sessions.save = false # Enable dump to a file on shutdown
pg_sessions.track_all_steps = true # Log for all Executor Hooks (small overhead but gives you an incremental view of the query consumtion)
pg_sessions.track_system_metrics = true # Disable the system metrics

And in postgresql :

CREATE EXTENSION pg_sessions;

View and function :

pg_sessions view :

postgres=# \d pg_sessions;
                     View "public.pg_sessions"
         Column          |            Type             | Modifiers
-------------------------+-----------------------------+-----------
 usename                 | name                        |
 datname                 | name                        |
 pid                     | bigint                      |
 queryid                 | bigint                      |
 query                   | text                        |
 calls                   | bigint                      |
 last_executed_timestamp | timestamp without time zone |
 status                  | text                        |
 total_time              | double precision            |
 min_time                | double precision            |
 max_time                | double precision            |
 mean_time               | double precision            |
 stddev_time             | double precision            |
 rows                    | bigint                      |
 shared_blks_hit         | bigint                      |
 shared_blks_read        | bigint                      |
 shared_blks_dirtied     | bigint                      |
 shared_blks_written     | bigint                      |
 local_blks_hit          | bigint                      |
 local_blks_read         | bigint                      |
 local_blks_dirtied      | bigint                      |
 local_blks_written      | bigint                      |
 temp_blks_read          | bigint                      |
 temp_blks_written       | bigint                      |
 blk_read_time           | double precision            |
 blk_write_time          | double precision            |
 user_time               | bigint                      |
 system_time             | bigint                      |
 virtual_memory_size     | text                        |
 resident_memory_size    | text                        |
 bytes_reads             | text                        |
 bytes_writes            | text                        |
 iops_reads              | bigint                      |
 iops_writes             | bigint                      |
 bytes_preads            | text                        |
 bytes_pwrites           | text                        |

Keep in mind that the metrics are pid/queryid based

Future addons :

• Wait events on postgresql 9.6 but may be difficult if not catchable using the hooks
• Add a custom background worker to collect and store for historical
• Go to a per pid/queryid/timestamp metric.