Re: TRUNCATE veeeery slow compared to DELETE in 7.4

for the clearer understanding: this is NOT about TRUNCATE being
slow "as such" vs. DELETE, but about a change in the order of
a (...) magnitude from 7.3.4 to 7.4...

here's some more info, plus test results w/a "full" db:

300 tables, 20000 pieces of modelled hw, so there's one table
w/20000 entries, each model has a special table (per type), too;
so, entries over all of them sum up to 20000; not all types are
present.
plus: some types (w/not many instances) have "very special" tables,
too, these sometimes w/lots of columns 500-1600...

alone on a sun fire-280 w/2 U-IIIi cpu's (well, only need one...):
all the time of the test, no vacuum anything was performed,
thus - by the book - making things worse... for the DELETE case.

7.4:
----
"full" database:
TRUNCATE: 0.03u 0.03s 1:21.40 0.0%
DELETE: 0.05u 0.01s 0:04.46 1.3%

empty database:
TRUNCATE:0.02u 0.05s 1:21.00 0.0%
DELETE: 0.04u 0.04s 0:01.32 6.0%

now for 7.3.4 database server (same machine, of cause):
--------------
"full" database:
TRUNCATE: 0.04u 0.04s 0:03.79 2.1%
DELETE: 0.03u 0.03s 0:06.51 0.9%

empty database:
TRUNCATE: 0.04u 0.05s 0:01.51 5.9%
DELETE: 0.01u 0.02s 0:01.00 3.0%

what can i say...
...please find the attached configs.

i reeeeally don't think this can be explained by table/index
complexity, it's the _same_ schema and contents for both cases,
they both were started w/createdb, they both were filled the same
way (by our server prog), there was no vacuum nowhere, test execution
order was the same in both cases.

P.S.: Mon pessimisme va jusqu'à suspecter la sincérité des pessimistes.
        - Jean Rostand (1894-1977), Journal d'un caractère, 1931

--
Hartmut "Hardy" Raschick / Dept. t2
ke Kommunikations-Elektronik GmbH
Wohlenberstr. 3, 30179 Hannover
Phone: ++49 (0)511 6747-564
Fax: ++49 (0)511 6747-340
e-Mail: hartmut.raschick@ke-elektronik.de
http://www.ke-elektronik.de#
# PostgreSQL configuration file
# -----------------------------
#
# This file consists of lines of the form:
#
#   name = value
#
# (The '=' is optional.) White space may be used. Comments are introduced
# with '#' anywhere on a line. The complete list of option names and
# allowed values can be found in the PostgreSQL documentation. The
# commented-out settings shown in this file represent the default values.
#
# Any option can also be given as a command line switch to the
# postmaster, e.g. 'postmaster -c log_connections=on'. Some options
# can be changed at run-time with the 'SET' SQL command.
#
# This file is read on postmaster startup and when the postmaster
# receives a SIGHUP. If you edit the file on a running system, you have
# to SIGHUP the postmaster for the changes to take effect, or use
# "pg_ctl reload".


#========================================================================


#
#    Connection Parameters
#
#tcpip_socket = false
tcpip_socket = true
#ssl = false

#max_connections = 32
max_connections = 128
#superuser_reserved_connections = 2

#port = 5432
port = 5433
#hostname_lookup = false
#show_source_port = false

#unix_socket_directory = ''
#unix_socket_group = ''
#unix_socket_permissions = 0777    # octal

#virtual_host = ''

#krb_server_keyfile = ''


#
#    Shared Memory Size
#
#shared_buffers = 64        # min max_connections*2 or 16, 8KB each
shared_buffers = 256           # 2*max_connections, min 16, typically 8KB each
#max_fsm_relations = 1000    # min 10, fsm is free space map, ~40 bytes
#max_fsm_pages = 10000        # min 1000, fsm is free space map, ~6 bytes
max_fsm_pages = 50000          # min 1000, fsm is free space map, ~6 bytes
#max_locks_per_transaction = 64    # min 10
#wal_buffers = 8        # min 4, typically 8KB each
wal_buffers = 40              # min 4, typically 8KB each

#
#    Non-shared Memory Sizes
#
#sort_mem = 1024        # min 64, size in KB
sort_mem = 16384                # min 64, size in KB
#vacuum_mem = 8192        # min 1024, size in KB
vacuum_mem = 16384              # min 1024, size in KB


#
#    Write-ahead log (WAL)
#
#checkpoint_segments = 3    # in logfile segments, min 1, 16MB each
checkpoint_segments = 20        # in logfile segments, min 1, 16MB each
#checkpoint_timeout = 300    # range 30-3600, in seconds
checkpoint_timeout = 600        # range 30-3600, in seconds
#
#commit_delay = 0               # range 0-100000, in microseconds
commit_delay = 100000            # range 0-100000, in microseconds
#commit_siblings = 5            # range 1-1000
commit_siblings = 100           # range 1-1000
#
#fsync = true
fsync = false
#wal_sync_method = fsync    # the default varies across platforms:
wal_sync_method = fdatasync    # the default varies across platforms:
#                # fsync, fdatasync, open_sync, or open_datasync
#wal_debug = 0            # range 0-16


#
#    Optimizer Parameters
#
#enable_seqscan = true
enable_seqscan = false
#enable_indexscan = true
#enable_tidscan = true
#enable_sort = true
#enable_nestloop = true
#enable_mergejoin = true
#enable_hashjoin = true

#effective_cache_size = 1000    # typically 8KB each
#random_page_cost = 4        # units are one sequential page fetch cost
#cpu_tuple_cost = 0.01        # (same)
#cpu_index_tuple_cost = 0.001    # (same)
#cpu_operator_cost = 0.0025    # (same)

#default_statistics_target = 10    # range 1-1000

#
#    GEQO Optimizer Parameters
#
#geqo = true
#geqo_selection_bias = 2.0    # range 1.5-2.0
#geqo_threshold = 11
#geqo_pool_size = 0        # default based on tables in statement,
                # range 128-1024
#geqo_effort = 1
#geqo_generations = 0
#geqo_random_seed = -1        # auto-compute seed


#
#    Message display
#
#server_min_messages = notice    # Values, in order of decreasing detail:
                #   debug5, debug4, debug3, debug2, debug1,
                #   info, notice, warning, error, log, fatal,
                #   panic
#client_min_messages = notice    # Values, in order of decreasing detail:
                #   debug5, debug4, debug3, debug2, debug1,
                #   log, info, notice, warning, error
#silent_mode = false

#log_connections = false
log_connections = true
#log_pid = false
#log_statement = false
#log_duration = false
#log_timestamp = false

#log_min_error_statement = error # Values in order of increasing severity:
                 #   debug5, debug4, debug3, debug2, debug1,
                 #   info, notice, warning, error, panic(off)

#debug_print_parse = false
#debug_print_rewritten = false
#debug_print_plan = false
#debug_pretty_print = false

#explain_pretty_print = true

# requires USE_ASSERT_CHECKING
#debug_assertions = true


#
#    Syslog
#
#syslog = 0            # range 0-2
#syslog_facility = 'LOCAL0'
#syslog_ident = 'postgres'


#
#    Statistics
#
#show_parser_stats = false
#show_planner_stats = false
#show_executor_stats = false
#show_statement_stats = false

# requires BTREE_BUILD_STATS
#show_btree_build_stats = false


#
#    Access statistics collection
#
#stats_start_collector = true
#stats_reset_on_server_start = true
#stats_command_string = false
#stats_row_level = false
#stats_block_level = false


#
#    Lock Tracing
#
#trace_notify = false

# requires LOCK_DEBUG
#trace_locks = false
#trace_userlocks = false
#trace_lwlocks = false
#debug_deadlocks = false
#trace_lock_oidmin = 16384
#trace_lock_table = 0


#
#    Misc
#
#autocommit = true
#dynamic_library_path = '$libdir'
#search_path = '$user,public'
#datestyle = 'iso, us'
#timezone = unknown        # actually, defaults to TZ environment setting
#australian_timezones = false
#client_encoding = sql_ascii    # actually, defaults to database encoding
#authentication_timeout = 60    # 1-600, in seconds
#deadlock_timeout = 1000    # in milliseconds
#default_transaction_isolation = 'read committed'
#max_expr_depth = 10000        # min 10
#max_files_per_process = 1000    # min 25
#password_encryption = true
#sql_inheritance = true
#transform_null_equals = false
#statement_timeout = 0        # 0 is disabled, in milliseconds
#db_user_namespace = false





#
#    Locale settings
#
# (initialized by initdb -- may be changed)
LC_MESSAGES = 'C'
LC_MONETARY = 'en_US.ISO8859-15'
LC_NUMERIC = 'en_US.ISO8859-15'
LC_TIME = 'en_US.ISO8859-15'
# -----------------------------
# PostgreSQL configuration file
# -----------------------------
#
# This file consists of lines of the form:
#
#   name = value
#
# (The '=' is optional.) White space may be used. Comments are introduced
# with '#' anywhere on a line. The complete list of option names and
# allowed values can be found in the PostgreSQL documentation. The
# commented-out settings shown in this file represent the default values.
#
# Any option can also be given as a command line switch to the
# postmaster, e.g. 'postmaster -c log_connections=on'. Some options
# can be changed at run-time with the 'SET' SQL command.
#
# This file is read on postmaster startup and when the postmaster
# receives a SIGHUP. If you edit the file on a running system, you have
# to SIGHUP the postmaster for the changes to take effect, or use
# "pg_ctl reload".


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

# - Connection Settings -

#tcpip_socket = false
tcpip_socket = true
max_connections = 128
    # note: increasing max_connections costs about 500 bytes of shared
    # memory per connection slot, in addition to costs from shared_buffers
        # and max_locks_per_transaction.
#superuser_reserved_connections = 2
#port = 5432
port = 5474
#unix_socket_directory = ''
#unix_socket_group = ''
#unix_socket_permissions = 0777    # octal
#virtual_host = ''        # what interface to listen on; defaults to any
#rendezvous_name = ''        # defaults to the computer name

# - Security & Authentication -

#authentication_timeout = 60    # 1-600, in seconds
#ssl = false
#password_encryption = true
#krb_server_keyfile = ''
#db_user_namespace = false


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

# - Memory -

shared_buffers = 1024    # min 16, at least max_connections*2, 8KB each
#sort_mem = 1024        # min 64, size in KB
sort_mem = 16384        # min 64, size in KB
#vacuum_mem = 8192        # min 1024, size in KB
vacuum_mem = 16384        # min 1024, size in KB

# - Free Space Map -

#max_fsm_pages = 20000        # min max_fsm_relations*16, 6 bytes each
max_fsm_pages = 50000          # min max_fsm_relations*16, 6 bytes each
#max_fsm_relations = 1000    # min 100, ~50 bytes each

# - Kernel Resource Usage -

#max_files_per_process = 1000    # min 25
#preload_libraries = ''


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

# - Settings -

#fsync = true            # turns forced synchronization on or off
fsync = false            # turns forced synchronization on or off
#wal_sync_method = fsync    # the default varies across platforms:
wal_sync_method = fdatasync    # the default varies across platforms:
                # fsync, fdatasync, open_sync, or open_datasync
#wal_buffers = 8        # min 4, 8KB each
wal_buffers = 40        # min 4, 8KB each

# - Checkpoints -

#checkpoint_segments = 3    # in logfile segments, min 1, 16MB each
checkpoint_segments = 20        # in logfile segments, min 1, 16MB each
#checkpoint_timeout = 300    # range 30-3600, in seconds
checkpoint_timeout = 600        # range 30-3600, in seconds
#checkpoint_warning = 30    # 0 is off, in seconds
#commit_delay = 0        # range 0-100000, in microseconds
commit_delay = 100000        # range 0-100000, in microseconds
#commit_siblings = 5        # range 1-1000
commit_siblings = 100        # range 1-1000


#---------------------------------------------------------------------------
# QUERY TUNING
#---------------------------------------------------------------------------

# - Planner Method Enabling -

#enable_hashagg = true
#enable_hashjoin = true
#enable_indexscan = true
#enable_mergejoin = true
#enable_nestloop = true
#enable_seqscan = true
enable_seqscan = false
#enable_sort = true
#enable_tidscan = true

# - Planner Cost Constants -

#effective_cache_size = 1000    # typically 8KB each
#random_page_cost = 4        # units are one sequential page fetch cost
#cpu_tuple_cost = 0.01        # (same)
#cpu_index_tuple_cost = 0.001    # (same)
#cpu_operator_cost = 0.0025    # (same)

# - Genetic Query Optimizer -

#geqo = true
#geqo_threshold = 11
#geqo_effort = 1
#geqo_generations = 0
#geqo_pool_size = 0        # default based on tables in statement,
                # range 128-1024
#geqo_selection_bias = 2.0    # range 1.5-2.0

# - Other Planner Options -

#default_statistics_target = 10    # range 1-1000
#from_collapse_limit = 8
#join_collapse_limit = 8    # 1 disables collapsing of explicit JOINs


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

# - Syslog -

#syslog = 0            # range 0-2; 0=stdout; 1=both; 2=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, info, 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 = panic # Values in order of increasing severity:
                 #   debug5, debug4, debug3, debug2, debug1,
                 #   info, notice, warning, error, panic(off)

#log_min_duration_statement = -1 # Log all statements whose
                 # execution time exceeds the value, in
                 # milliseconds.  Zero prints all queries.
                 # Minus-one disables.

#silent_mode = false         # DO NOT USE without Syslog!

# - What to Log -

#debug_print_parse = false
#debug_print_rewritten = false
#debug_print_plan = false
#debug_pretty_print = false
#log_connections = false
log_connections = true
#log_duration = false
#log_pid = false
#log_statement = false
#log_timestamp = false
#log_hostname = false
#log_source_port = false


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

# - Statistics Monitoring -

#log_parser_stats = false
#log_planner_stats = false
#log_executor_stats = false
#log_statement_stats = false

# - Query/Index Statistics Collector -

#stats_start_collector = true
#stats_command_string = false
#stats_block_level = false
#stats_row_level = false
#stats_reset_on_server_start = true


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

# - Statement Behavior -

#search_path = '$user,public'    # schema names
#check_function_bodies = true
#default_transaction_isolation = 'read committed'
#default_transaction_read_only = false
#statement_timeout = 0        # 0 is disabled, in milliseconds

# - Locale and Formatting -

#datestyle = 'iso, mdy'
#timezone = unknown        # actually, defaults to TZ environment setting
#australian_timezones = false
#extra_float_digits = 0        # min -15, max 2
#client_encoding = sql_ascii    # actually, defaults to database encoding

# These settings are initialized by initdb -- they may be changed
lc_messages = 'C'        # locale for system error message strings
lc_monetary = 'en_US.ISO8859-15'        # locale for monetary formatting
lc_numeric = 'en_US.ISO8859-15'        # locale for number formatting
lc_time = 'en_US.ISO8859-15'            # locale for time formatting

# - Other Defaults -

#explain_pretty_print = true
#dynamic_library_path = '$libdir'
#max_expr_depth = 10000        # min 10

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

#deadlock_timeout = 1000    # in milliseconds
#max_locks_per_transaction = 64    # min 10, ~260*max_connections bytes each


#---------------------------------------------------------------------------
# VERSION/PLATFORM COMPATIBILITY
#---------------------------------------------------------------------------

# - Previous Postgres Versions -

#add_missing_from = true
#regex_flavor = advanced    # advanced, extended, or basic
#sql_inheritance = true

# - Other Platforms & Clients -

#transform_null_equals = false