Melhorando a utilização de RAM e CPU pelo PostgreSQL 9.6

Eu tenho executado uma função no banco de dados que está entrando em cada tabela, ALTER COLUMNem todas as colunas de um determinado tipo de dados, e CASTpara remover zeros à direita. Cerca de 115 tabelas variando de alguns milhares de registros a algumas centenas de milhares de registros. Ele está funcionando há quase 24 horas e meu cálculo aproximado até o tempo de conclusão é de cerca de 58 horas.

Eu tenho htoppara cima e verificá-lo regularmente.

Devo mencionar que esta é uma instalação limpa do CentOS mínima de ontem com realmente apenas o PostgreSQL 9.6.5 nele. Duas CPUs quad core e 32 GB de RAM.

De acordo com htopmeu mem está em 620M/31.3Ge maximiza um núcleo por vez, nunca realmente utilizando outros núcleos ao mesmo tempo. Parece que eu tenho muito espaço para a utilização da CPU e da RAM. Parece que se eu pudesse configurar corretamente o PostgreSQL para utilizar mais CPU e RAM, o processo como estou executando agora seria muito mais rápido. Talvez eu esteja errado.

Quais são algumas configurações que podem ser ajustadas, seja no Postgres ou no CentOS, que permitirão maior utilização?

O meu postgresql.confestá praticamente nas configurações padrão:

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

# - Memory -

shared_buffers = 128MB                  # min 128kB
                                        # (change requires restart)
#huge_pages = try                       # on, off, or try
                                        # (change requires restart)
#temp_buffers = 8MB                     # min 800kB
#max_prepared_transactions = 0          # zero disables the feature
                                        # (change requires restart)
# Caution: it is not advisable to set max_prepared_transactions nonzero unless
# you actively intend to use prepared transactions.
#work_mem = 4MB                         # min 64kB
#maintenance_work_mem = 64MB            # min 1MB
#replacement_sort_tuples = 150000       # limits use of replacement selection sort
#autovacuum_work_mem = -1               # min 1MB, or -1 to use maintenance_work_mem
#max_stack_depth = 2MB                  # min 100kB
dynamic_shared_memory_type = posix      # the default is the first option
                                        # supported by the operating system:
                                        #   posix
                                        #   sysv
                                        #   windows
                                        #   mmap
                                        # use none to disable dynamic shared memory
                                        # (change requires restart)

# - Disk -

#temp_file_limit = -1                   # limits per-process temp file space
                                        # in kB, or -1 for no limit

# - 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                  # 0-100 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 multiplier on buffers scanned/round
#bgwriter_flush_after = 512kB           # measured in pages, 0 disables

# - Asynchronous Behavior -

#effective_io_concurrency = 1           # 1-1000; 0 disables prefetching
#max_worker_processes = 8               # (change requires restart)
#max_parallel_workers_per_gather = 0    # taken from max_worker_processes
#old_snapshot_threshold = -1            # 1min-60d; -1 disables; 0 is immediate
                                        # (change requires restart)
#backend_flush_after = 0                # measured in pages, 0 disables


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

# - Settings -

#wal_level = minimal                    # minimal, replica, or logical
                                        # (change requires restart)
#fsync = on                             # flush data to disk for crash safety
                                                # (turning this off can cause
                                                # unrecoverable data corruption)
#synchronous_commit = on                # synchronization level;
                                        # off, local, remote_write, remote_apply, or on
#wal_sync_method = fsync                # the default is the first option
                                        # supported by the operating system:
                                        #   open_datasync
                                        #   fdatasync (default on Linux)
                                        #   fsync
                                        #   fsync_writethrough
                                        #   open_sync
#full_page_writes = on                  # recover from partial page writes
#wal_compression = off                  # enable compression of full-page writes
#wal_log_hints = off                    # also do full page writes of non-critical updates
                                        # (change requires restart)
#wal_buffers = -1                       # min 32kB, -1 sets based on shared_buffers
                                        # (change requires restart)
#wal_writer_delay = 200ms               # 1-10000 milliseconds
#wal_writer_flush_after = 1MB           # measured in pages, 0 disables

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

# - Checkpoints -

#checkpoint_timeout = 5min              # range 30s-1d
#max_wal_size = 1GB
#min_wal_size = 80MB
#checkpoint_completion_target = 0.5     # checkpoint target duration, 0.0 - 1.0
#checkpoint_flush_after = 256kB         # measured in pages, 0 disables
#checkpoint_warning = 30s               # 0 disables

# - Archiving -

#archive_mode = off             # enables archiving; off, on, or always
                                # (change requires restart)
#archive_command = ''           # command to use to archive a logfile segment
                                # placeholders: %p = path of file to archive
                                #               %f = file name only
                                # e.g. 'test ! -f /mnt/server/archivedir/%f && cp %p /mnt/server/archivedir/%f'
#archive_timeout = 0            # force a logfile segment switch after this
                                # number of seconds; 0 disables


#------------------------------------------------------------------------------
# REPLICATION
#------------------------------------------------------------------------------

# - Sending Server(s) -

# Set these on the master and on any standby that will send replication data.

#max_wal_senders = 0            # max number of walsender processes
                                # (change requires restart)
#wal_keep_segments = 0          # in logfile segments, 16MB each; 0 disables
#wal_sender_timeout = 60s       # in milliseconds; 0 disables

#max_replication_slots = 0      # max number of replication slots
                                # (change requires restart)
#track_commit_timestamp = off   # collect timestamp of transaction commit
                                # (change requires restart)

# - Master Server -

# These settings are ignored on a standby server.

#synchronous_standby_names = '' # standby servers that provide sync rep
                                # number of sync standbys and comma-separated list of application_name
                                # from standby(s); '*' = all
#vacuum_defer_cleanup_age = 0   # number of xacts by which cleanup is delayed

# - Standby Servers -

# These settings are ignored on a master server.

#hot_standby = off                      # "on" allows queries during recovery
                                        # (change requires restart)
#max_standby_archive_delay = 30s        # max delay before canceling queries
                                        # when reading WAL from archive;
                                        # -1 allows indefinite delay
#max_standby_streaming_delay = 30s      # max delay before canceling queries
                                        # when reading streaming WAL;
                                        # -1 allows indefinite delay
#wal_receiver_status_interval = 10s     # send replies at least this often
                                        # 0 disables
#hot_standby_feedback = off             # send info from standby to prevent
                                        # query conflicts
#wal_receiver_timeout = 60s             # time that receiver waits for
                                        # communication from master
                                        # in milliseconds; 0 disables
#wal_retrieve_retry_interval = 5s       # time to wait before retrying to
                                        # retrieve WAL after a failed attempt


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

# - Planner Method Configuration -

#enable_bitmapscan = on
#enable_hashagg = on
#enable_hashjoin = on
#enable_indexscan = on
#enable_indexonlyscan = on
#enable_material = 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
#parallel_tuple_cost = 0.1              # same scale as above
#parallel_setup_cost = 1000.0   # same scale as above
#min_parallel_relation_size = 8MB
#effective_cache_size = 4GB

# - 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
#geqo_seed = 0.0                        # range 0.0-1.0

# - Other Planner Options -

#default_statistics_target = 100        # range 1-10000
#constraint_exclusion = partition       # on, off, or partition
#cursor_tuple_fraction = 0.1            # range 0.0-1.0
#from_collapse_limit = 8
#join_collapse_limit = 8                # 1 disables collapsing of explicit
                                        # JOIN clauses
#force_parallel_mode = off


#------------------------------------------------------------------------------
# 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-%a.log'      # log file name pattern,
                                        # can include strftime() escapes
#log_file_mode = 0600                   # creation mode for log files,
                                        # begin with 0 to use octal notation
log_truncate_on_rotation = on           # If on, an existing log file with 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 disables.
log_rotation_size = 0                   # Automatic rotation of logfiles will
                                        # happen after that much log output.
                                        # 0 disables.

# These are relevant when logging to syslog:
#syslog_facility = 'LOCAL0'
#syslog_ident = 'postgres'
#syslog_sequence_numbers = on
#syslog_split_messages = on

# This is only relevant when logging to eventlog (win32):
# (change requires restart)
#event_source = 'PostgreSQL'

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

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 number
                                        # of milliseconds


# - What to Log -

#debug_print_parse = off
#debug_print_rewritten = off
#debug_print_plan = off
#debug_pretty_print = on
#log_checkpoints = off
log_connections = off
#log_disconnections = off
#log_duration = off
log_error_verbosity = default           # terse, default, or verbose messages
#log_hostname = off
log_line_prefix = '< %m > '                     # special values:
                                        #   %a = application name
                                        #   %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
                                        #   %n = timestamp with milliseconds (as a Unix epoch)
                                        #   %i = command tag
                                        #   %e = SQL state
                                        #   %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_replication_commands = off
#log_temp_files = -1                    # log temporary files equal or larger
                                        # than the specified size in kilobytes;
                                        # -1 disables, 0 logs all temp files
log_timezone = 'US/Pacific'


# - Process Title -

#cluster_name = ''                      # added to process titles if nonempty
                                        # (change requires restart)
#update_process_title = on


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

# - Query/Index Statistics Collector -

#track_activities = on
#track_counts = on
#track_io_timing = off
#track_functions = none                 # none, pl, all
#track_activity_query_size = 1024       # (change requires restart)
#stats_temp_directory = 'pg_stat_tmp'


# - 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 this number
                                        # of milliseconds.
#autovacuum_max_workers = 3             # max number of autovacuum subprocesses
                                        # (change requires restart)
#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_multixact_freeze_max_age = 400000000        # maximum multixact age
                                        # before forced vacuum
                                        # (change requires restart)
#autovacuum_vacuum_cost_delay = 20ms    # default vacuum cost delay for
                                        # autovacuum, in milliseconds;
                                        # -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
#default_transaction_deferrable = off
#session_replication_role = 'origin'
#statement_timeout = 0                  # in milliseconds, 0 is disabled
#lock_timeout = 0                       # in milliseconds, 0 is disabled
#idle_in_transaction_session_timeout = 0                # in milliseconds, 0 is disabled
#vacuum_freeze_min_age = 50000000
#vacuum_freeze_table_age = 150000000
#vacuum_multixact_freeze_min_age = 5000000
#vacuum_multixact_freeze_table_age = 150000000
#bytea_output = 'hex'                   # hex, escape
#xmlbinary = 'base64'
#xmloption = 'content'
#gin_fuzzy_search_limit = 0
#gin_pending_list_limit = 4MB

# - Locale and Formatting -

datestyle = 'iso, mdy'
#intervalstyle = 'postgres'
timezone = 'US/Pacific'
#timezone_abbreviations = 'Default'     # Select the set of available time zone
                                        # abbreviations.  Currently, there are
                                        #   Default
                                        #   Australia (historical usage)
                                        #   India
                                        # You can create your own file in
                                        # share/timezonesets/.
#extra_float_digits = 0                 # min -15, max 3
#client_encoding = sql_ascii            # actually, defaults to database
                                        # encoding

# These settings are initialized by initdb, but they can be changed.
lc_messages = 'en_US.UTF-8'                     # locale for system error message
                                        # strings
lc_monetary = 'en_US.UTF-8'                     # locale for monetary formatting
lc_numeric = 'en_US.UTF-8'                      # locale for number formatting
lc_time = 'en_US.UTF-8'                         # locale for time formatting

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

# - Other Defaults -

#dynamic_library_path = '$libdir'
#local_preload_libraries = ''
#session_preload_libraries = ''


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

#deadlock_timeout = 1s
#max_locks_per_transaction = 64         # min 10
                                        # (change requires restart)
#max_pred_locks_per_transaction = 64    # min 10
                                        # (change requires restart)


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

# - Previous PostgreSQL Versions -

#array_nulls = on
#backslash_quote = safe_encoding        # on, off, or safe_encoding
#default_with_oids = off
#escape_string_warning = on
#lo_compat_privileges = off
#operator_precedence_warning = off
#quote_all_identifiers = off
#sql_inheritance = on
#standard_conforming_strings = on
#synchronize_seqscans = on

# - Other Platforms and Clients -

#transform_null_equals = off


#------------------------------------------------------------------------------
# ERROR HANDLING
#------------------------------------------------------------------------------

#exit_on_error = off                    # terminate session on any error?
#restart_after_crash = on               # reinitialize after backend crash?


#------------------------------------------------------------------------------
# CONFIG FILE INCLUDES
#------------------------------------------------------------------------------

# These options allow settings to be loaded from files other than the
# default postgresql.conf.

#include_dir = 'conf.d'                 # include files ending in '.conf' from
                                        # directory 'conf.d'
#include_if_exists = 'exists.conf'      # include file only if it exists
#include = 'special.conf'               # include file


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

# Add settings for extensions here