Update table performance

I have a table with 4,889,820 records in it. The
table also has 47 fields. I'm having problems with
update performance. Just as a test, I issued the
following update:

update valley set test='this is a test'

This took 905641 ms. Isn't that kind of slow? There
aren't any indexes, triggers, constraints or anything
on this table. The version of Postgres is "PostgreSQL
8.2.4 on i686-pc-mingw32, compiled by GCC gcc.exe
(GCC) 3.4.2 (mingw-special)". The operating
environment is Windows 2003 Standard Edition w/service
pack 2. It is 2.20 Ghz with 1.0 GB of RAM. Here is
the results from Explain:

"Seq Scan on valley (cost=0.00..1034083.57
rows=4897257 width=601)"

Here are the settings in the postgresql.conf. Any
ideas or is this the expected speed?

#---------------------------------------------------------------------------
# CONNECTIONS AND AUTHENTICATION
#---------------------------------------------------------------------------

# - Connection Settings -

listen_addresses = '*' # what IP address(es) to
listen on;
# comma-separated list of addresses;
# defaults to 'localhost', '*' = all
# (change requires restart)
port = 5432 # (change requires restart)
max_connections = 20 # (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 # octal
# (change requires restart)
#bonjour_name = '' # defaults to the computer name
# (change requires restart)

# - Security & Authentication -

#authentication_timeout = 1min # 1s-600s
#ssl = off # (change requires restart)
#password_encryption = on
#db_user_namespace = off

# Kerberos
#krb_server_keyfile = '' # (change requires restart)
#krb_srvname = 'postgres' # (change requires restart)
#krb_server_hostname = '' # empty string matches any
keytab entry
# (change requires restart)
#krb_caseins_users = off # (change requires restart)

# - 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 = 512MB # 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 = 8MB # min 64kB
maintenance_work_mem = 16MB # min 1MB
#max_stack_depth = 4MB # min 100kB

# - Free Space Map -

max_fsm_pages = 700000 # 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 = '' # (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 # 0-10000 credits

# - Background writer -

#bgwriter_delay = 200ms # 10-10000ms between rounds
#bgwriter_lru_percent = 1.0 # 0-100% of LRU buffers
scanned/round
#bgwriter_lru_maxpages = 5 # 0-1000 buffers max
written/round
#bgwriter_all_percent = 0.333 # 0-100% of all buffers
scanned/round
#bgwriter_all_maxpages = 5 # 0-1000 buffers max
written/round

#---------------------------------------------------------------------------
# WRITE AHEAD LOG
#---------------------------------------------------------------------------

# - Settings -

fsync = off # turns forced synchronization on or
off
#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 = off # recover from partial page
writes
#wal_buffers = 64kB # min 32kB
# (change requires restart)
#commit_delay = 0 # range 0-100000, in microseconds
#commit_siblings = 5 # range 1-1000

# - Checkpoints -

checkpoint_segments = 60 # in logfile segments, min
1, 16MB each
checkpoint_timeout = 5min # range 30s-1h
checkpoint_warning = 0 # 0 is off

# - Archiving -

archive_command = '' # command to use to archive a
logfile segment
archive_timeout = 0 # force a logfile segment switch
after this
# many seconds; 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 = 32MB

# - 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
# JOINs

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

# - Where to Log -

log_destination = 'stderr' # Valid values are
combinations of
# stderr, syslog and eventlog,
# depending on platform.

# This is used when logging to stderr:
redirect_stderr = on # Enable capturing of stderr
into log
# files
# (change requires restart)

# These are only used if redirect_stderr 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, any 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
increasing severity:
# debug5
# debug4
# debug3
# debug2
# debug1
# info
# notice
# warning
# error
# fatal
# panic (effectively off)

#log_min_duration_statement = -1 # -1 is disabled, 0
logs all statements
# and their durations.

#silent_mode = off # DO NOT USE without syslog or
# redirect_stderr
# (change requires restart)

# - What to Log -

#debug_print_parse = off
#debug_print_rewritten = off
#debug_print_plan = off
#debug_pretty_print = off
#log_connections = off
#log_disconnections = off
#log_duration = off
log_line_prefix = '%t ' # Special values:
# %u = user name
# %d = database name
# %r = remote host and port
# %h = remote host
# %p = PID
# %t = timestamp (no milliseconds)
# %m = timestamp with milliseconds
# %i = command tag
# %c = session id
# %l = session line number
# %s = session start timestamp
# %x = transaction id
# %q = stop here in non-session
# processes
# %% = '%'
# e.g. '<%u%%%d> '
#log_statement = 'none' # none, ddl, mod, all
#log_hostname = off

#---------------------------------------------------------------------------
# RUNTIME STATISTICS
#---------------------------------------------------------------------------

# - Query/Index Statistics Collector -

#stats_command_string = on
#update_process_title = on

stats_start_collector = on # needed for block or row
stats
# (change requires restart)
#stats_block_level = off
stats_row_level = on
#stats_reset_on_server_start = off # (change requires
restart)

# - 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 stats_start_collector
# and stats_row_level to also be on
#autovacuum_naptime = 1min # time between autovacuum
runs
#autovacuum_vacuum_threshold = 500 # min # of tuple
updates before
# vacuum
#autovacuum_analyze_threshold = 250 # min # of tuple
updates before
# analyze
#autovacuum_vacuum_scale_factor = 0.2 # fraction of
rel size before
# vacuum
#autovacuum_analyze_scale_factor = 0.1 # fraction of
rel size before
# analyze
#autovacuum_freeze_max_age = 200000000 # maximum XID
age before forced vacuum
# (change requires restart)
#autovacuum_vacuum_cost_delay = -1 # 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
#check_function_bodies = on
#default_transaction_isolation = 'read committed'
#default_transaction_read_only = off
#statement_timeout = 0 # 0 is disabled
#vacuum_freeze_min_age = 100000000

# - Locale and Formatting -

datestyle = 'iso, mdy'
#timezone = unknown # actually, defaults to TZ
# environment setting
#timezone_abbreviations = 'Default' # select the
set of available timezone
# abbreviations. Currently, there are
# Default
# Australia
# India
# However you can also 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 -- they
might 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

# - Other Defaults -

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

#---------------------------------------------------------------------------
# LOCK MANAGEMENT
#---------------------------------------------------------------------------

#deadlock_timeout = 1s
max_locks_per_transaction = 384 # 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 Postgres 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
#standard_conforming_strings = off
#regex_flavor = advanced # advanced, extended, or
basic
#sql_inheritance = on

# - Other Platforms & Clients -

#transform_null_equals = off

#---------------------------------------------------------------------------
# CUSTOMIZED OPTIONS
#---------------------------------------------------------------------------

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

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