Mastering PostgreSQL Administration

Mastering
PostgreSQL Administration

BRUCE MOMJIAN,
ENTERPRISEDB

April, 2009

Abstract
POSTGRESQL is an open-source, full-featured relational database.
This presentation covers advanced administration topics.

Creative Commons Attribution License http://momjian.us/presentations

Introduction

Installation

Conﬁguration

Maintenance

Monitoring

Recovery

Mastering PostgreSQL Administration 1

Installation

Click-Through installers

– MS Windows
– Linux
– OS/X
– Solaris

Ports

– RPM
– DEB
– PKG
– other packages

Source

– obtaining
– build options
– installing

Initialization (initdb)

$ initdb
The files belonging to this database system will be owned by user "postgres".
This user must also own the server process.
The database cluster will be initialized with locale C.
The default database encoding has accordingly been set to SQL_ASCII.
The default text search configuration will be set to "english".
creating directory /u/pg/data ... ok
creating subdirectories ... ok
selecting default max_connections ... 100
selecting default shared_buffers/max_fsm_pages ... 32MB/204800
creating configuration files ... ok
creating template1 database in /u/pg/data/base/1 ... ok
initializing pg_authid ... ok
initializing dependencies ... ok
creating system views ... ok
loading system objects’ descriptions ... ok
creating conversions ... ok
creating dictionaries ... ok
setting privileges on built-in objects ... ok
creating information schema ... ok
vacuuming database template1 ... ok
copying template1 to template0 ... ok
copying template1 to postgres ... ok

Initialization (continued)

WARNING: enabling "trust" authentication for local connections
You can change this by editing pg_hba.conf or using the -A option the
next time you run initdb.

Success. You can now start the database server using:

postgres -D /u/pg/data
or
pg_ctl -D /u/pg/data -l logfile start


pg_controldata
pg_control version number: 74
Catalog version number: 200502281
Database system identifier: 4766833642862247929
Database cluster state: shut down
pg_control last modified: 03/03/05 10:49:18
Current log file ID: 0
Next log file segment: 1
Latest checkpoint location: 0/A34010
Prior checkpoint location: 0/A2D5C0
Latest checkpoint’s REDO location: 0/A34010
Latest checkpoint’s UNDO location: 0/0
Latest checkpoint’s TimeLineID: 1
Latest checkpoint’s NextXID: 545
Latest checkpoint’s NextOID: 17233
Time of latest checkpoint: 03/03/05 10:49:18
Database block size: 8192
Blocks per segment of large relation: 131072
Bytes per WAL segment: 16777216
Maximum length of identifiers: 64
Maximum number of function arguments: 32
Date/time type storage: floating-point numbers
Maximum length of locale name: 128
LC_COLLATE: C
LC_CTYPE: C

System Architecture

Main
Libpq

Postmaster

Postgres Postgres

Parse Statement

utility Utility
Traffic Cop
Command
Query e.g. CREATE TABLE, COPY
SELECT, INSERT, UPDATE, DELETE

Rewrite Query

Generate Paths
Optimal Path

Generate Plan
Plan

Execute Plan

Utilities Catalog Storage Managers

Access Methods Nodes / Lists

Starting Postmaster

LOG: database system was shut down at 2009-01-27 10:32:05 EST
LOG: database system is ready to accept connections
LOG: autovacuum launcher started

manually

pg_ctl

on boot


Stopping Postmaster

LOG: received smart shutdown request
LOG: autovacuum launcher shutting down
LOG: shutting down
LOG: database system is shut down

manually

pg_ctl

on shutdown


Connections

local — unix domain socket

host — TCP/IP, both SSL or non-SSL

hostssl — only SSL

hostnossl — never SSL


Authentication

trust

passwords

– md5
– crypt
– password

remote authentication

– host ident using pg_ident.conf
– kerberos
– gss
– sspi


Authentication (continued)

local socket ident

host ident using local identd

socket permissions

pam

ldap

reject


Access

hostname and network mask

database name

role name (user or group)

ﬁlename or list of databases, role

IPv6


Pg_hba.conf

# TYPE DATABASE USER CIDR-ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all trust
# IPv4 local connections:
host all all 127.0.0.1/32 trust
# IPv6 local connections:
host all all ::1/128 trust


Permissions

host connection permissions

role permissions

– create roles
– create databases
– table permissions

Database creation

– template1 customization
– system tables
– disk space computations


Data Directory

$ ls -CF
PG_VERSION pg_ident.conf pg_xlog/
base/ pg_multixact/ postgresql.conf
global/ pg_subtrans/ postmaster.opts
pg_clog/ pg_tblspc/ postmaster.pid
pg_hba.conf pg_twophase/


Database Directories

$ ls -CF global/
1136 2397 2843
1137 2671 2844
1213 2672 2845
1214 2676 2846
1232 2677 2847
1233 2694 pg_auth
1260 2695 pg_control
1261 2697 pg_database
1262 2698 pgstat.stat
2396 2842

$ ls -CF base/
1/ 11510/ 11511/ 16384/

$ ls -CF base/16384
11429 2617 2696
11431 2618 2699
...

Transaction/WAL Directories

$ ls -CF pg_xlog/
000000010000000000000000 archive_status/
$ ls -CF pg_clog/
0000


Conﬁguration Directories

$ ls -CF share/
conversion_create.sql postgres.description sql_features.txt
information_schema.sql postgres.shdescription system_views.sql
pg_hba.conf.sample postgresql.conf.sample timezone/
pg_ident.conf.sample psqlrc.sample timezonesets/
pg_service.conf.sample recovery.conf.sample tsearch_data/
postgres.bki snowball_create.sql unknown.pltcl


Conﬁguration Postgresql.conf


PostgreSQL.Conf

# -----------------------------
# PostgreSQL configuration file
# -----------------------------
#
# This file consists of lines of the form:
#
# name = value
#
# (The "=" is optional.) Whitespace may be used. Comments are introduced with
# "#" anywhere on a line. The complete list of parameter names and allowed
# values can be found in the PostgreSQL documentation.
#
# The commented-out settings shown in this file represent the default values.
# Re-commenting a setting is NOT sufficient to revert it to the default value;
# you need to reload the server.


PostgreSQL.Conf (Continued)

# This file is read on server startup and when the server receives a SIGHUP
# signal. If you edit the file on a running system, you have to SIGHUP the
# server for the changes to take effect, or use "pg_ctl reload". Some
# parameters, which are marked below, require a server shutdown and restart to
# take effect.
#
# Any parameter can also be given as a command-line option to the server, e.g.,
# "postgres -c log_connections=on". Some paramters can be changed at run time
# with the "SET" SQL command.
#
# Memory units: kB = kilobytes MB = megabytes GB = gigabytes
# Time units: ms = milliseconds s = seconds min = minutes h = hours d = days


Conﬁguration File Location

#data_directory = ’ConfigDir’ # use data in another directory
# (change requires restart)
#hba_file = ’ConfigDir/pg_hba.conf’ # host-based authentication file
#ident_file = ’ConfigDir/pg_ident.conf’ # ident configuration file
# If external_pid_file is not explicitly set, no extra PID file is written.
#external_pid_file = ’(none)’ # write an extra PID file


Connections and Authentication

#listen_addresses = ’localhost’ # what IP address(es) to listen on;
# comma-separated list of addresses;
# defaults to ’localhost’, ’*’ = all
#port = 5432 # (change requires restart)
max_connections = 100 # (change requires restart)
# Note: Increasing max_connections costs ~400 bytes of shared memory per
# connection slot, plus lock space (see max_locks_per_transaction). You might
# also need to raise shared_buffers to support more connections.
#superuser_reserved_connections = 3 # (change requires restart)
#unix_socket_directory = ’’ # (change requires restart)
#unix_socket_group = ’’ # (change requires restart)
#unix_socket_permissions = 0777 # begin with 0 to use octal notation
#bonjour_name = ’’ # defaults to the computer name


Security and Authentication

#authentication_timeout = 1min # 1s-600s
#ssl = off # (change requires restart)
#ssl_ciphers = ’ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH’ # allowed SSL ciphers
#password_encryption = on
#db_user_namespace = off
# Kerberos and GSSAPI
#krb_server_keyfile = ’’ # (change requires restart)
#krb_-
srvname = ’postgres’ # (change requires restart, Kerberos only)
#krb_server_hostname = ’’ # empty string matches any keytab entry
# (change requires restart, Ker-
beros only)
#krb_caseins_users = off # (change requires restart)
#krb_realm = ’’ # (change requires restart)


TCP/IP Control

# see "man 7 tcp" for details
#tcp_keepalives_idle = 0 # TCP_KEEPIDLE, in seconds;
# 0 selects the system default
#tcp_keepalives_interval = 0 # TCP_KEEPINTVL, in seconds;
#tcp_keepalives_count = 0 # TCP_KEEPCNT;


Memory Usage

shared_buffers = 32MB # min 128kB or max_connections*16kB
#temp_buffers = 8MB # min 800kB
#max_prepared_transactions = 5 # can be 0 or more
# Note: Increasing max_prepared_transactions costs ~600 bytes of shared memory
# per transaction slot, plus lock space (see max_locks_per_transaction).
#work_mem = 1MB # min 64kB
#maintenance_work_mem = 16MB # min 1MB
#max_stack_depth = 2MB # min 100kB

Kernel changes often required.


Sizing Shared Memory

Postgres Backend

Postgres Backend

Postgres Backend
R
PostgreSQL Shared Buffer Cache
A
Kernel Disk Buffer Cache Page Out
M
Swap
Free
Page In
Kernel


Free Space Map and Kernel Resources

# - Free Space Map -
max_fsm_pages = 204800 # min max_fsm_relations*16, 6 bytes each
#max_fsm_relations = 1000 # min 100, ~70 bytes each

# - Kernel Resource Usage -
#max_files_per_process = 1000 # min 25
#shared_preload_libraries = ’’ # (change requires restart)


Vacuum and Background Writer

# - Cost-Based Vacuum Delay -
#vacuum_cost_delay = 0 # 0-1000 milliseconds
#vacuum_cost_page_hit = 1 # 0-10000 credits
#vacuum_cost_page_miss = 10 # 0-10000 credits
#vacuum_cost_page_dirty = 20 # 0-10000 credits
#vacuum_cost_limit = 200 # 1-10000 credits

# - Background Writer -
#bgwriter_delay = 200ms # 10-10000ms between rounds
#bgwriter_lru_maxpages = 100 # 0-1000 max buffers written/round
#bgwriter_lru_multiplier = 2.0 # 0-
10.0 multipler on buffers scanned/round


Write-Ahead Log (WAL)

#fsync = on # turns forced synchronization on or off
#synchronous_commit = on # immediate fsync at commit
#wal_sync_method = fsync # the default is the first option
# supported by the operating system:
# open_datasync
# fdatasync
# fsync
# fsync_writethrough
# open_sync
#full_page_writes = on # recover from partial page writes
#wal_buffers = 64kB # min 32kB
#wal_writer_delay = 200ms # 1-10000 milliseconds
#commit_delay = 0 # range 0-100000, in microseconds
#commit_siblings = 5 # range 1-1000


Write-Ahead Logging (Continued)
Postgres Postgres Postgres
Backend Backend Backend

PostgreSQL Shared Buffer Cache Write−Ahead Log

fsync

Kernel Disk Buffer Cache

fsync

Disk Blocks


Checkpoints and Archiving

# - Checkpoints -
#checkpoint_segments = 3 # in logfile segments, min 1, 16MB each
#checkpoint_timeout = 5min # range 30s-1h
#checkpoint_completion_target = 0.5 # checkpoint target duration, 0.0 - 1.0
#checkpoint_warning = 30s # 0 is off

# - Archiving -
#archive_mode = off # allows archiving to be done
#archive_command = ’’ # command to use to archive a logfile segment
#archive_timeout = 0 # force a logfile segment switch after this
# time; 0 is off


Query Tuning

# - Planner Method Configuration -
#enable_bitmapscan = on
#enable_hashagg = on
#enable_hashjoin = on
#enable_indexscan = on
#enable_mergejoin = on
#enable_nestloop = on
#enable_seqscan = on
#enable_sort = on
#enable_tidscan = on

# - Planner Cost Constants -
#seq_page_cost = 1.0 # measured on an arbitrary scale
#random_page_cost = 4.0 # same scale as above
#cpu_tuple_cost = 0.01 # same scale as above
#cpu_index_tuple_cost = 0.005 # same scale as above
#cpu_operator_cost = 0.0025 # same scale as above
#effective_cache_size = 128MB

Query Tuning (Continued)

#geqo = on
#geqo_threshold = 12
#geqo_effort = 5 # range 1-10
#geqo_pool_size = 0 # selects default based on effort
#geqo_generations = 0 # selects default based on effort
#geqo_selection_bias = 2.0 # range 1.5-2.0

# - Other Planner Options -
#default_statistics_target = 10 # range 1-1000
#constraint_exclusion = off
#from_collapse_limit = 8
#join_collapse_limit = 8 # 1 disables collapsing of explicit
# JOIN clauses


Where To Log

#log_destination = ’stderr’ # Valid values are combinations of
# stderr, csvlog, syslog and eventlog,
# depending on platform. csvlog
# requires logging_collector to be on.
# This is used when logging to stderr:
#logging_collector = off # Enable capturing of stderr and csvlog
# into log files. Required to be on for
# csvlogs.
# These are only used if logging_collector is on:
#log_directory = ’pg_log’ # directory where log files are written,
# can be absolute or relative to PGDATA
#log_filename = ’postgresql-%Y-%m-%d_%H%M%S.log’ # log file name pattern,
# can include strftime() escapes


Where To Log (Continued)

#log_truncate_on_rotation = off # If on, an existing log file of the
# same name as the new log file will be
# truncated rather than appended to.
# But such truncation only occurs on
# time-driven rotation, not on restarts
# or size-driven rotation. Default is
# off, meaning append to existing files
# in all cases.
#log_rotation_age = 1d # Automatic rotation of logfiles will
# happen after that time. 0 to disable.
#log_rotation_size = 10MB # Automatic rotation of logfiles will
# happen after that much log output.
# 0 to disable.

# These are relevant when logging to syslog:
#syslog_facility = ’LOCAL0’
#syslog_ident = ’postgres’

When to Log

#client_min_messages = notice # values in order of decreasing detail:
# debug5
# debug4
# debug3
# debug2
# debug1
# log
# notice
# warning
# error
#log_min_messages = notice # values in order of decreasing detail:
# debug5
# debug4
# debug3
# debug2
# debug1
# info
# notice
# warning
# error
# log
# fatal
# panic

When to Log (Continued)

#log_error_verbosity = default # terse, default, or verbose messages
#log_min_error_statement = error # values in order of decreasing detail:
# debug5
# debug4
# debug3
# debug2
# debug1
# info
# notice
# warning
# error
# log
# fatal
# panic (effectively off)
#log_min_duration_statement = -1 # -1 is disabled, 0 logs all statements
# and their durations, > 0 logs only
# statements running at least this time.
#silent_mode = off # DO NOT USE without syslog or
# logging_collector


What to Log

#debug_print_parse = off
#debug_print_rewritten = off
#debug_print_plan = off
#debug_pretty_print = off
#log_checkpoints = off
#log_connections = off
#log_disconnections = off
#log_duration = off
#log_hostname = off


What To Log: Log_line_preﬁx

#log_line_prefix = ’’ # special values:
# %u = user name
# %d = database name
# %r = remote host and port
# %h = remote host
# %p = process ID
# %t = timestamp without milliseconds
# %m = timestamp with milliseconds
# %i = command tag
# %c = session ID
# %l = session line number
# %s = session start timestamp
# %v = virtual transaction ID
# %x = transaction ID (0 if none)
# %q = stop here in non-session
# processes
# %% = ’%’
# e.g. ’<%u%%%d> ’

What to Log (Continued)

#log_lock_waits = off # log lock waits >= deadlock_timeout
#log_statement = ’none’ # none, ddl, mod, all
#log_temp_files = -1 # log temporary files equal or larger
# than specified size;
# -1 disables, 0 logs all temp files
#log_timezone = unknown # actually, defaults to TZ environment
# setting


Runtime Statistics

# - Query/Index Statistics Collector -
#track_activities = on
#track_counts = on
#update_process_title = on

# - Statistics Monitoring -
#log_parser_stats = off
#log_planner_stats = off
#log_executor_stats = off
#log_statement_stats = off


Autovacuum

#autovacuum = on # Enable autovacuum subprocess? ’on’
# requires track_counts to also be on.
#log_autovacuum_min_duration = -1 # -1 disables, 0 logs all actions and
# their durations, > 0 logs only
# actions running at least that time.
#autovacuum_max_workers = 3 # max number of autovacuum subprocesses
#autovacuum_naptime = 1min # time between autovacuum runs
#autovacuum_vacuum_threshold = 50 # min number of row updates before
# vacuum
#autovacuum_analyze_threshold = 50 # min number of row updates before
# analyze
#autovacuum_vacuum_scale_factor = 0.2 # fraction of table size before vacuum
#autovacuum_analyze_scale_factor = 0.1 # fraction of table size before analyze
#autovacuum_freeze_max_age = 200000000 # maximum XID age before forced vacuum
#autovacuum_vacuum_cost_delay = 20 # default vacuum cost delay for
# autovacuum, -1 means use
# vacuum_cost_delay
#autovacuum_vacuum_cost_limit = -1 # default vacuum cost limit for
# autovacuum, -1 means use
# vacuum_cost_limit


Statement Behavior

#search_path = ’"$user",public’ # schema names
#default_tablespace = ’’ # a tablespace name, ’’ uses the default
#temp_tablespaces = ’’ # a list of tablespace names, ’’ uses
# only default tablespace
#check_function_bodies = on
#default_transaction_isolation = ’read committed’
#default_transaction_read_only = off
#session_replication_role = ’origin’
#statement_timeout = 0 # 0 is disabled
#vacuum_freeze_min_age = 100000000
#xmlbinary = ’base64’
#xmloption = ’content’


Locale and Formatting

datestyle = ’iso, mdy’
#timezone = unknown # actually, defaults to TZ environment
# setting
#timezone_abbreviations = ’Default’ # Select the set of available time zone
# abbreviations. Currently, there are
# Default
# Australia
# India
# You can create your own file in
# share/timezonesets/.
#extra_float_digits = 0 # min -15, max 2
#client_encoding = sql_ascii # actually, defaults to database
# encoding
# These settings are initialized by initdb, but they can be changed.
lc_messages = ’C’ # locale for system error message
# strings
lc_monetary = ’C’ # locale for monetary formatting
lc_numeric = ’C’ # locale for number formatting
lc_time = ’C’ # locale for time formatting

Full Text Search

# default configuration for text search
default_text_search_config = ’pg_catalog.english’


Other Defaults

#explain_pretty_print = on
#dynamic_library_path = ’$libdir’
#local_preload_libraries = ’’


Lock Management

#deadlock_timeout = 1s
#max_locks_per_transaction = 64 # min 10
# Note: Each lock table slot uses ~270 bytes of shared memory, and there are
# max_locks_per_transaction * (max_connections + max_prepared_transactions)
# lock table slots.


Version/Platform Compatibility

# - Previous PostgreSQL Versions -
#add_missing_from = off
#array_nulls = on
#backslash_quote = safe_encoding # on, off, or safe_encoding
#default_with_oids = off
#escape_string_warning = on
#regex_flavor = advanced # advanced, extended, or basic
#sql_inheritance = on
#standard_conforming_strings = off
#synchronize_seqscans = on

# - Other Platforms and Clients -
#transform_null_equals = off


Customization

#custom_variable_classes = ’’ # list of custom variable class names


Interfaces

Installing

– Compiled Languages (C, ecpg)
– Scripting Language (Perl, Python)
– SPI

Connection Pooling


Include Files

$ ls -CF include/
ecpg_config.h libpq/ pgtypes_interval.h
ecpg_informix.h libpq-fe.h pgtypes_numeric.h
ecpgerrno.h pg_config.h pgtypes_timestamp.h
ecpglib.h pg_config_manual.h postgres_ext.h
ecpgtype.h pg_config_os.h server/
informix/ pgtypes_date.h sql3types.h
internal/ pgtypes_error.h sqlca.h


Library Files

$ ls -CF lib/
ascii_and_mic.so* libecpg_compat.so.3@ utf8_and_big5.so*
cyrillic_and_mic.so* libecpg_compat.so.3.0* utf8_and_cyrillic.so*
dict_snowball.so* libpgport.a utf8_and_euc_cn.so*
euc_cn_and_mic.so* libpgtypes.a utf8_and_euc_jis_2004.s
euc_jis_2004_and_shift_ libpgtypes.so@ utf8_and_euc_jp.so*
euc_jp_and_sjis.so* libpgtypes.so.3@ utf8_and_euc_kr.so*
euc_kr_and_mic.so* libpgtypes.so.3.0* utf8_and_euc_tw.so*
euc_tw_and_big5.so* libpq.a utf8_and_gb18030.so*
latin2_and_win1250.so* libpq.so@ utf8_and_gbk.so*
latin_and_mic.so* libpq.so.5@ utf8_and_iso8859.so*
libecpg.a libpq.so.5.1* utf8_and_iso8859_1.so*
libecpg.so@ pgxs/ utf8_and_johab.so*
libecpg.so.6@ plperl.so* utf8_and_shift_jis_2004
libecpg.so.6.0* plpgsql.so* utf8_and_sjis.so*
libecpg_compat.a pltcl.so* utf8_and_uhc.so*
libecpg_compat.so@ utf8_and_ascii.so* utf8_and_win.so*

Maintenance


Backup

File system-level

– tar, cpio while shutdown
– ﬁle system snapshot
– rsync, shutdown, rsync, restart

pg_dump/pg_dumpall

restore/pg_restore with custom format


Continuous Archiving /
Point-In-Time Recovery (PITR)
00

00

00

00
02

09

11

13
WAL
AL AL
W W

File System- Continuous
Level Backup Backup

PITR Backup Procedures

1. archive_command = ’cp %p /mnt/server/pgsql/%f ’

2. SELECT pg_start_backup(’label’);

3. Perform ﬁle system-level backup (can be inconsistent)

4. SELECT pg_stop_backup();


PITR Recovery
00

30

40

55
17

17

17

17
WAL
AL AL
W W

File System- Continuous
Level Backup Backup


PITR Recovery Procecdures

1. Stop postmaster

2. Restore ﬁle system-level backup

3. Make adjustments as outlined in the documentation

4. Create recovery.conf

5. Add restore_command = ’cp /mnt/server/pgsql/%f %p’

6. Start the postmaster


60
Master-Slave Replication - Slony

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Mastering PostgreSQL Administration

Other Solutions

Mutli-master replication: pgcluster, bacardo

Pooling: pgpool


Data Maintenance

VACUUM (nonblocking), free space map

VACUUM FULL

ANALYZE


Vacuum

Free Space Map

Table Block # Block # Block #

DB oid
Relfilenode Table Block # Block #

Table Block # Block # Block #

Hashed

Shared Memory


Vacuum Full

A A E A A A E A A A A A
Original Heap C C X C C C X C C C C C
T T P T T T P T T T T T
With Expired I I I I I I I I I I I I
V V R V V V R V V V V V
Rows Identified E E E E E E E E E E E E

A A A A A A A A A A
Move Trailing C C C C C C C C C C
T T T T T T T T T T
Rows Into Expired I I I I I I I I I I
V V V V V V V V V V
Slots E E E E E E E E E E

A A A A A A A A A A
C C C C C C C C C C
T T T T T T T T T T
Truncate File I I I I I I I I I I
V V V V V V V V V V
E E E E E E E E E E


Checkpoints

Write all dirty shared buffers

Sync all dirty kernel buffers

Recycle WAL ﬁles

Check for server messages indicating too-frequent checkpoints

If so, increase checkpoint_segments


Automating Tasks

0 3 * * * root psql -c ’VACUUM FULL;’ test
0 3 * * * root vacuumdb -a -f

Autovacuum usually makes vacuum administration unnecessary.


Monitoring Active Sessions


ps

$ ps -Upostgres
PID TT STAT TIME COMMAND
2125 ?? Ss 0:00.26 ./bin/postmaster -i
2142 ?? S 0:00.03 stats buffer process (postmaster)
2143 ?? S 0:00.06 stats collector process (postmaster)
3341 ?? I 0:00.07 postgres test [local] idle (postmaster)
3340 p6 I+ 0:00.03 psql test


top

$ top
load averages: 0.56, 0.39, 0.36 18:25:58
138 processes: 5 running, 130 sleeping, 3 zombie
CPU states: 50.0% user, 0.0% nice, 0.0% system, 0.0% interrupt, 50.0% idle
Memory: Real: 96M/133M Virt: 535M/1267M Free: 76M

PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND
23785 postgres 57 0 11M 5336K run/0 0:07 30.75% 30.66% postmaster
23784 postgres 2 0 10M 11M sleep 0:00 2.25% 2.25% psql


pgmonitor


pgmonitor


Analyzing Activity

Heavily used tables

Unnecessary indexes

Additional indexes

Index usage

TOAST usage


CPU

$ vmstat 5
procs memory page disks faults cpu
r b w avm fre flt re pi po fr sr s0 s0 in sy cs us sy id
1 0 0 501820 48520 1234 86 2 0 0 3 5 0 263 2881 599 10 4 86
3 0 0 512796 46812 1422 201 12 0 0 0 3 0 259 6483 827 4 7 88
3 0 0 542260 44356 788 137 6 0 0 0 8 0 286 5698 741 2 5 94
4 0 0 539708 41868 576 65 13 0 0 0 4 0 273 5721 819 16 4 80
4 0 0 547200 32964 454 0 0 0 0 0 5 0 253 5736 948 50 4 46
4 0 0 556140 23884 461 0 0 0 0 0 2 0 249 5917 959 52 3 44
1 0 0 535136 46280 1056 141 25 0 0 0 2 0 261 6417 890 24 6 70


I/O

$ iostat 5
tty sd0 sd1 sd2 % cpu
tin tout sps tps msps sps tps msps sps tps msps usr nic sys int idl
7 119 244 11 6.1 0 0 27.3 0 0 18.1 9 1 4 0 86
0 86 20 1 1.4 0 0 0.0 0 0 0.0 2 0 2 0 96
0 82 61 4 3.6 0 0 0.0 0 0 0.0 2 0 2 0 97
0 65 6 0 0.0 0 0 0.0 0 0 0.0 1 0 2 0 97
12 90 31 2 5.4 0 0 0.0 0 0 0.0 4 0 3 0 93
24 173 6 0 4.9 0 0 0.0 0 0 0.0 48 0 3 0 49
0 91 3594 63 4.6 0 0 0.0 0 0 0.0 11 0 4 0 85


Disk Usage

play=# SELECT relfilenode, relpages * 8 AS kilobytes
play-# FROM pg_class
play-# WHERE relname = ’customer’;
relfilenode | kilobytes
-------------+----------
16806 | 480
(1 row)

Vacuum required. dbsize available.


TOAST Usage

play=# SELECT relname, relpages * 8 AS kilobytes
play-# WHERE relname = ’pg_toast_16806’ OR
play-# relname = ’pg_toast_16806_index’
play-# ORDER BY relname;
relname | kilobytes
----------------------+----------
pg_toast_16806 | 0
pg_toast_16806_index | 1


Index Usage

play=# SELECT c2.relname, c2.relpages * 8 AS kilobytes
play-# FROM pg_class c, pg_class c2, pg_index i
play-# WHERE c.relname = ’customer’ AND
play-# c.oid = i.indrelid AND
play-# c2.oid = i.indexrelid
play-# ORDER BY c2.relname;
relname | kilobytes
----------------------+----------
customer_id_indexdex | 26


Largest Tables

play=# SELECT relname, relpages * 8
play-# ORDER BY relpages DESC;
relname | kilobytes
----------------------+----------
bigtable | 3290
customer | 3144


Database File Mapping - oid2name

$ oid2name
All databases:
---------------------------------
18720 = test1
1 = template1
18719 = template0
18721 = test
18735 = postgres
18736 = cssi


Table File Mapping

$ cd /usr/local/pgsql/data/base
$ oid2name
All databases:
---------------------------------
16817 = test2
16578 = x
16756 = test
1 = template1
16569 = template0
16818 = test3
16811 = floattest

$ cd 16756
$ ls 1873*
18730 18731 18732 18735 18736 18737 18738 18739


$ oid2name -d test -o 18737
Tablename of oid 18737 from database test:
---------------------------------
18737 = ips

$ oid2name -d test -t ips
Oid of table ips from database test:
---------------------------------
18737 = ips

$ # show disk space for every db object
$ du * | while read SIZE RELFILENODE
do
echo $SIZE ‘oid2name -q -d test -o $RELFILENODE‘
done
24 18737 = ips
36 18722 = cities
...


$ # same as above, but sort by largest first
$ du * | while read SIZE OID
do
echo $SIZE ‘oid2name -q -d test -o $OID‘
done |
sort -rn
2048 19324 = bigtable
1950 23903 = customers
...

$ # show disk usage per database
$ cd /usr/local/pgsql/data/base
$ du -s * |
while read SIZE OID
do
echo $SIZE ‘oid2name -q | grep ^$OID’ ’‘
done |
sort -rn
2256 18721 = test
2135 18735 = postgres

Disk Balancing

Move pg_xlog to another drive using symlinks

Tablespaces


Per-Database Tablespaces

DB1 DB2 DB3 DB4

Disk 1 Disk 2 Disk 3

Per-Object Tablespaces

tab1 tab2 index constraint

Disk 1 Disk 2 Disk 3

Analyzing Locking

$ ps -Upostgres
PID TT STAT TIME COMMAND
9874 ?? I 0:00.07 postgres test [local] idle in transaction (postmaster)
9835 ?? S 0:00.05 postgres test [local] UPDATE waiting (postmaster)
10295 ?? S 0:00.05 postgres test [local] DELETE waiting (postmaster)

test= SELECT * FROM pg_locks;
relation | database | transaction | pid | mode | granted
----------+----------+-------------+------+------------------+---------
17143 | 17142 | | 9173 | AccessShareLock | t
17143 | 17142 | | 9173 | RowExclusiveLock | t
| | 472 | 9380 | ExclusiveLock | t
| | 468 | 9338 | ShareLock | f
17143 | 17142 | | 9338 | RowExclusiveLock | t
(9 rows)

Miscellaneous Tasks

Log ﬁle rotation, syslog

Upgrading

Migration


Administration Tools

pgadmin

phppgadmin


Recovery


Client Application Crash

Nothing Required. Transactions in progress are rolled back.


Graceful Server Crash



Abrupt Server Crash



Operating System Crash

Nothing Required. Transactions in progress are rolled back. Partial page
writes are repaired.


Disk Failure

Restore from previous backup or use PITR.


Accidental DELETE

Recover table from previous backup, perhaps using pg_restore. It is
possible to modify the backend code to make deleted tuples visible,
dump out the deleted table and restore the original code. All tuples in
the table since the previous vacuum will be visible. It is possible to
restrict that so only tuples deleted by a speciﬁc transaction are visible.


Write-Ahead Log (WAL) Corruption

See pg_resetxlog. Review recent transactions and identify any damage,
including partially committed transactions.


File Deletion

It may be necessary to create an empty ﬁle with the deleted ﬁle name so
the object can be deleted, and then the object restored from backup.


Accidental DROP TABLE

Restore from previous backup.


Accidental DROP INDEX

Recreate index.


Accidental DROP DATABASE

Restore from previous backup.


Non-Starting Installation

Restart problems are usually caused by write-ahead log problems. See
pg_resetxlog. Review recent transactions and identify any damage,
including partially committed transactions.


Index Corruption

Use REINDEX.


Table Corruption

Try reindexing the table. Try identifying the corrupt OID of the row and
transfer the valid rows into another table using SELECT…INTO…WHERE
oid != ###. Use http://sources.redhat.com/rhdb/tools.html to analyze
the internal structure of the table.


Conclusion


Mastering PostgreSQL Administration

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