The document outlines essential parameters and settings for configuring PostgreSQL's postgresql.conf file, including types of settings, when they take effect, and common 'gotchas'. Key topics include memory sizing, logging, connection management, checkpoint and vacuum management, and WAL management for performance and replication. The presentation emphasizes best practices for achieving optimal database performance and provides additional resources for further learning.

1. The Essential
PostgreSQL.conf
9
Robert Treat, JDCon East 2011
Thursday, March 31, 2011

2. Introduction
• Robert Treat
• OmniTI
• Database Management and Consulting
• Large and/or High Traffic Architectures
• We’re Hiring!
• Postgres
• Web, Advocacy, Conferences, PhpPgAdmin
• Major Contributor
• xzilla.net
• @robtreat2
Thursday, March 31, 2011

3. Introduction
• Robert Treat
• OmniTI
• Database Management and Consulting
• Large and/or High Traffic Architectures
• We’re Hiring!
• Postgres
• Web, Advocacy, Conferences, PhpPgAdmin
• Major Contributor
• xzilla.net
• @robtreat2
Thursday, March 31, 2011

4. The Grand Scheme
• Understanding the postgresql.conf
• Essential postgresql.conf parameters
Thursday, March 31, 2011

5. The Grand Scheme
• Understanding the postgresql.conf
• Essential postgresql.conf parameters
Thursday, March 31, 2011

6. Understanding the postgresql.conf
• Types of Settings
• When Settings Take Effect
• PostgreSQL.conf “Gotchas”
• Viewing Your Current Settings
Thursday, March 31, 2011

7. Types of Settings
Thursday, March 31, 2011

8. Types of Settings
• Boolean: true, false, on, off
Thursday, March 31, 2011

9. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
Thursday, March 31, 2011

10. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
• Float: decimal values (21.12)
Thursday, March 31, 2011

11. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
• Float: decimal values (21.12)
• Memory/Disk Units: 128MB, 2112GB
Thursday, March 31, 2011

12. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
• Float: decimal values (21.12)
• Memory/Disk Units: 128MB, 2112GB
• Avoid using integers to size memory parameters
Thursday, March 31, 2011

13. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
• Float: decimal values (21.12)
• Memory/Disk Units: 128MB, 2112GB
• Avoid using integers to size memory parameters
• Time: d,m,s (30s)
Thursday, March 31, 2011

14. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
• Float: decimal values (21.12)
• Memory/Disk Units: 128MB, 2112GB
• Avoid using integers to size memory parameters
• Time: d,m,s (30s)
• Strings: single quotes (‘pg_log’)
Thursday, March 31, 2011

15. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
• Float: decimal values (21.12)
• Memory/Disk Units: 128MB, 2112GB
• Avoid using integers to size memory parameters
• Time: d,m,s (30s)
• Strings: single quotes (‘pg_log’)
• Enum: single quotes (‘WARNING’ or ‘ERROR’)
Thursday, March 31, 2011

16. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
• Float: decimal values (21.12)
• Memory/Disk Units: 128MB, 2112GB
• Avoid using integers to size memory parameters
• Time: d,m,s (30s)
• Strings: single quotes (‘pg_log’)
• Enum: single quotes (‘WARNING’ or ‘ERROR’)
• Limited set of acceptable strings
Thursday, March 31, 2011

17. Types of Settings
• Boolean: true, false, on, off
• Integer: whole numbers (2112)
• Float: decimal values (21.12)
• Memory/Disk Units: 128MB, 2112GB
• Avoid using integers to size memory parameters
• Time: d,m,s (30s)
• Strings: single quotes (‘pg_log’)
• Enum: single quotes (‘WARNING’ or ‘ERROR’)
• Limited set of acceptable strings
• Lists: comma seperated (‘“$user”,public,tsearch2’)
Thursday, March 31, 2011

18. When Settings Take Effect
• Internal: set at compile time
• Postmaster: requires database restart
• Backend: must be set before session start
• Sighup: change by reloading conf file
• pg_reload_conf(), pg_ctl reload, kill -HUP
• Superuser: set at runtime by superuser
• User: set at runtime, affects only a single session
See pg_settings.context to determine setting type
Thursday, March 31, 2011

19. When Settings Take Effect
• Internal: set at compile time
• Postmaster: requires database restart
• Backend: must be set before session start
• Sighup: change by reloading conf file
• pg_reload_conf(), pg_ctl reload, kill -HUP
• Superuser: set at runtime by superuser
• User: set at runtime, affects only a single session
See pg_settings.context to determine setting type
Thursday, March 31, 2011

20. postgresql.conf Gotchas!
• Where is my postgresql.conf ?
• $PGDATA/postgresql.conf
• watch out for symbolic links
• some distros put it in other places (/etc)
• SHOW data_directory;
• SHOW config_file;
Thursday, March 31, 2011

21. postgresql.conf Gotchas!
• Lines with #
• This line is a comment, and has no effect
• On a fresh install, uses defaults
• Commenting a line is the same as deleting a line,
it will restore the “default” for that instance
Thursday, March 31, 2011

22. Viewing Your Current Settings
• Look in postgresql.conf
• Works if you follow best practices
• Not definitive!
Thursday, March 31, 2011

23. Viewing Your Current Settings
• Look in postgresql.conf
• Works if you follow best practices
• Not definitive!
• SHOW ALL, SHOW <setting>,
current_setting(setting)
• Shows the current value
• Watch out for session specific changes
Thursday, March 31, 2011

24. Viewing Your Current Settings
• Look in postgresql.conf
• Works if you follow best practices
• Not definitive!
• SHOW ALL, SHOW <setting>,
current_setting(setting)
• Shows the current value
• Watch out for session specific changes
• SELECT * FROM pg_settings
• Shows the current value
• “source” column
Thursday, March 31, 2011

25. Viewing Your Current Settings
pagila=# select current_setting(name), * from pg_settings
where name = 'shared_buffers';
-[ RECORD 1 ]------+----------------------------------------------
current_setting | 1600kB
name | shared_buffers
setting | 200
unit | 8kB
category | Resource Usage / Memory
short_desc | Sets the number of shared memory buffers used by the server.
extra_desc |
context | postmaster
vartype | integer
source | configuration file
min_val | 16
max_val | 1073741823
enumvals |
boot_val | 1024
reset_val | 200
sourcefile | /opt/local/var/db/postgresql91/data/postgresql.conf
sourceline | 109
Thursday, March 31, 2011

26. The Essential Parameters
• Logging
• Getting Connected
• Sizing Memory
• Checkpoint Management
• Vacuum Managment
• WAL management
Thursday, March 31, 2011

27. Logging
• log_destination, log_directory, log_filename
• find out where you are logging
• might be good to log to a different disk than your data
Thursday, March 31, 2011

28. Logging
• log_destination, log_directory, log_filename
• find out where you are logging
• might be good to log to a different disk than your data
• log_line_prefix
• generic recommendation: ‘%t: %r: %u@%d: [%p]: ‘
• timestamp, connecting host, username, database, pid
Thursday, March 31, 2011

29. Get Connected
• listen_addresses
• requires restart!
• default is localhost only
• use * to enable tcp/ip
Thursday, March 31, 2011

30. Get Connected
• listen_addresses
• requires restart!
• default is localhost only
• use * to enable tcp/ip
• max_connections
• requires restart!
• 100 default (apache children default is higher)
• affects other settings (work_mem)
• for 1000+ connections, use connection pooler
Thursday, March 31, 2011

31. Sizing Memory
• shared_buffers
• requires restart!
• most important setting for good performance
• allocation of memory for Postgres caching
• ~20% of Total Available RAM (up to 2GB)
• 32GB RAM, 1920 MB is probably ok
• 256GB RAM, 50 GB is probably not optimal
• Windows users probably want less
• may require adjusting kernel params (shmmax)
• http://www.postgresql.org/docs/current/interactive/kernel-resources.html
Thursday, March 31, 2011

32. Sizing Memory
• effective_cache_size
• most important setting for good performance
• based on memory available for filesystem cache
• SET = TRAM - (DRAM - PGRAM)
• TRAM = Total RAM
• DRAM = RAM needed by OS and other apps
• PGRAM = RAM needed for Postgres (shared_buffers, etc...)
• Guide for available memory, not an allocation
Thursday, March 31, 2011

33. Sizing Memory
• work_mem
• used by queries for sorting
• higher values for more complex queries
• limit is per sort
• 5 sorts in 1 query = 5*work_mem
• maintenance_work_mem
• used by vacuum, indexing, and similar operations
• semi-allocation of memory when needed
• don’t be scared to make this big (1GB)
Thursday, March 31, 2011

34. Checkpoint Management
• checkpoint_segments
• controls the amount of data required per checkpoint
• default 3, recommended minimum of 10
• set higher for heavy write activity
• 30 - 300 is not uncommon
• increases space needed in pg_xlog
• increases recovery time after crash
• checkpoint_completion_target
• with checkpoint_segments >= 10, set this to .9
• http://www.westnet.com/~gsmith/content/postgresql/chkp-bgw-83.htm
Thursday, March 31, 2011

35. Vacuum Management
• autovacuum
• max_fsm_pages
• max_fsm_relations
• default_statistics_target
• autovacuum_freeze_max_age
• set to 1,000,000,000 to reduce vacuums for non-activity
• requires restart
Thursday, March 31, 2011

36. WAL Management / Replication
• WAL for Performance
• wal_buffers
• requires restart!
• needed for write heavy loads
• 16MB, “set it and forget it!”
• synchronous_commit
• can increase tps by a large margin
• allows data loss without corruption
• BAD: fsync = off
• GOOD: synchronous_commit = off
• can be set per database, user, or transaction
Thursday, March 31, 2011

37. WAL Management / Replication
• WAL for Replication
• wal_level
• requires restart!
• “hot_standby” needed for... hot standbys
• max_wal_senders
• requires restart!
• controls the number of connections for streaming
replication
Thursday, March 31, 2011

38. The End
Thanks!
Additional Resources
http://www.postgresql.org/docs/current/interactive/runtime-config.html
http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server
Slides
http://www.xzilla.net/writings.html
Thursday, March 31, 2011

39. No Really, The End
Thursday, March 31, 2011