How to use postgresql.conf to configure and tune the PostgreSQL server

© Copyright EnterpriseDB Corporation, 2020. All rights reserved.
How to use
postgresql.conf to
configure and tune the
Postgres server
Raghavendra Rao; Managing Consultant
Marc Linster; SVP, Product Development and
Support
Bruce Momjian; Postgres Evangelist
1

Welcome – Housekeeping
Items
• Slides and recording will be available in next 48 hours
• Submit questions via GotoWebinar – will be answering at end
• We will be sharing info about EDB and Postgres later
2

Webinar Series
Feb 19 2020 Conquering Data Migration from Oracle to Postgres
March 4 2020 Using Terraform to deploy highly available Postgres
March 18 2020
How to use postgresql.conf to configure and tune the
Postgres server
April 1 2020
Optimizing Performance and Security with Platform
Native Packaging
April 15 2020 Window Functions in Postgres
3

Agenda
● Who is EDB?
● About postgresql.conf
● Interacting with postgresql.conf
○ Allowed change context (reload, restart, recompile)
○ Ways to change and apply settings
● Parameters classification
● Tuning recommendations
● Tuning Tools
● Q & A
© Copyright EnterpriseDB Corporation, 2020. All rights reserved.4

About postgresql.conf

CONFIDENTIAL © Copyright EnterpriseDB Corporation, 2020. All rights reserved.6
About postgresql.conf
A configuration parameter file that resides in Postgres cluster(data directory) to specify the server
behavior on connection, memory, logging, vacuuming and other behaviors.
File specifications:
• Located in $PGDATA/postgresql.conf (some distro puts in /etc)
• A plain text with tunable settings
• Each parameter preceded by pound sign (‘#’)
• At the beginning they are set with default values
• Number of tunable parameters in postgresql.conf file - 270+

Interacting with postgresql.conf
• Every setting in file consists of
name = value
• “name” is a parameter name/Grand Unified Configuration(GUC)
• “value” is a unit that parameter accepts, which can be boolean, integer,
float, units(kB/MB/GB/TB), time(ms,s,min,h,d), strings and lists.
Example:
shared_buffers = 1GB

Allowed change context
Every configuration setting has an associated context in which it’s allowed to be changed. There are set of context types:
• Internal - a parameter can only be set at compile time
• postmaster - a parameter is updated only when a full server restart is done
• signup - a parameter is changed by sending server a HUP signal(pg_ctl reload)
• backend - a parameter is similar to “sighup”, however changes will not impact any already running database backend sessions.
Only new sessions will accept the new changes.
• superuser-backend - a parameter is similar to “sighup”, however changes will not impact any already running database backend
sessions. Only new sessions will accept the new changes.(only super user change the settings)
• superuser - a parameter can be changed by any database superuser
• user - a parameter can be changed by the individual user in his session(per-session basis)
Query to find specific configuration information:pg_settings.context distinct values:

Ways to change and apply settings
As per parameter context, to update values there two ways change
• Reload
• pg_reload_conf()
• pg_ctl -D <data_directory> reload (SIGHUP)
• HUP postmaster
• Restart
• pg_ctl restart
• OS Service restart
• Other Changes
• ALTER SYSTEM
• ALTER DATABASE <dbname> SET <parameter setting>
• ALTER USER <username> SET <parameter setting>
• Session Level
• BEGIN.. SET <parameter setting>; END;

Parameter classifications….1

Tuning Recommendations...1
shared_buffers 15% to 25% of available RAM
maintenance_work_mem Total RAM * 0.15 / autovacuum_max_workers
work_mem Total RAM * 0.25 / max_connections
max_connections Start with default 100, if required prefer connection
pooler
effective_cache_size 75% of Total RAM
wal_buffers 1/32nd of shared_buffers capped at 16MB
bgwriter_delay Default 200ms, lower it if heavy writes
bgwriter_lru_maxpages
bgwriter_lru_multiplier
Increase multiplier on system with a heavy write
load.

Tuning Recommendations...2
wal_level Set according to the replication requirement
min_wal_size (GB)
max_wal_size (GB)
Setting it too low means checkpoints will occur too
frequently, increasing will beneficial for recovery
times.
checkpoint_completion_target Higher the value, the smoother the IO of the
checkpoint
checkpoint_timeout Increase this parameter can increase the amount
of the time needed for crash recovery
random_page_cost Increasing will result index being used over
sequential scans
cpu_tuple_cost Specifies the relative cost of the processing each
row during a query.

Tools

Tuning Tools
Few tools will automatically tune by analyzing the server resources and configure PostgreSQL
server for optimal performance.
• Open Source
• pgtune - https://pgtune.leopard.in.ua/#/
• pgbadger (a Log Analyzer) - http://pgbadger.darold.net/
• For EDB Customers
• EDB Postgres Enterprise Manager - Tuning Wizard/Postgres Expert
Useful Links:
• https://wiki.postgresql.org/wiki/Performance_Optimization
• https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server

24
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QUESTIONS

Tuning concerns or operational worries
about Postgres?
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