Postgresql.conf变量

Question

I have been playing around with the postgresql.conf file for a couple days now. I was wondering what variables you guys like customizing and why?

Here is a sample of the file:

# - TCP Keepalives -
# 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;
                    # 0 selects the system default
#tcp_keepalives_count = 0       # TCP_KEEPCNT;
                    # 0 selects the system default


#------------------------------------------------------------------------------
# RESOURCE USAGE (except WAL)
#------------------------------------------------------------------------------

# - Memory -

shared_buffers = 64MB           # min 128kB or max_connections*16kB
                    # (change requires restart)
#temp_buffers = 8MB         # min 800kB
#max_prepared_transactions = 5      # can be 0 or more
                    # (change requires restart)
# 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

# - Free Space Map -

max_fsm_pages = 204800          # min max_fsm_relations*16, 6 bytes each
                    # (change requires restart)
#max_fsm_relations = 1000       # min 100, ~70 bytes each
                    # (change requires restart)

# - Kernel Resource Usage -

#max_files_per_process = 1000       # min 25
                    # (change requires restart)
shared_preload_libraries = '$libdir/plugins/plugin_debugger.dll'        # (change requires restart)

# - 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
#------------------------------------------------------------------------------

# - Settings -

#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
                    # (change requires restart)
#wal_writer_delay = 200ms       # 1-10000 milliseconds

#commit_delay = 0           # range 0-100000, in microseconds
#commit_siblings = 5            # range 1-1000

# - 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
                # (change requires restart)
#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 = 32768

# - Genetic Query Optimizer -

#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


#------------------------------------------------------------------------------
# ERROR REPORTING AND LOGGING
#------------------------------------------------------------------------------

# - 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 = on      # Enable capturing of stderr and csvlog
                    # into log files. Required to be on for
                    # csvlogs.
                    # (change requires restart)

# 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
#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

#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
                    # (change requires restart)

# - 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
log_line_prefix = '%t '         # 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> '
#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 PARAMETERS
#------------------------------------------------------------------------------

#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
                    # (change requires restart)
#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


#------------------------------------------------------------------------------
# CLIENT CONNECTION DEFAULTS
#------------------------------------------------------------------------------

# - 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, dmy'
#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 = 'English_Canada'          # locale for system error message
                    # strings
lc_monetary = 'English_Canada'          # locale for monetary formatting
lc_numeric = 'English_Canada'           # locale for number formatting
lc_time = 'English_Canada'              # locale for time formatting

# 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
                    # (change requires restart)
# 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 = on
#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

I am mostly looking for efficiency or wise use of resources. I know it depends on how I am planning on using it and other such "it depends" answers. What I am looking for is the important or common variables customizations; which ones do people most often change and why?

Thx!

Answer 1

It's impossible to know what might be appropriate to change without knowing how you are going to use the database. Will you have a high transaction load? Will you have mostly static bulk data with a lot of queries? Will you be mostly reading existing data (SELECT), adding new data (INSERT), or changing existing data (UPDATE)?

Also, even knowing how you are using it, you will need to do benchmarks and query plan analysis to determine what aspect of the configuration you might need to change to address any performance problems you are encountering. This may require the assistance of a PostgreSQL expert.

The defaults will be suitable for all but the most demanding of applications.