1

Hope you're doing good.

I've recently moved from Amazon RDS to my own PostgreSQL instance in Hetzner (in order to colocate it with the server and reduce the roundtrip).

However I think that some config may be off, because a query went from taking less than a second to taking almost 300%.

This is the query:

SELECT * FROM "public"."Summary" WHERE "public"."Summary"."id" IN (67521,67522,67523,67524,67525,67526,67527,67528,...,68048);

There are 488 numbers in that IN statement. (note: I don't want to change the query per se, just debug why the 4x performance difference between hetzner and amazon rds)

This is the table Schema

[
  {
    "table_name": "Summary",
    "column_name": "id",
    "data_type": "integer"
  },
  {
    "table_name": "Summary",
    "column_name": "info",
    "data_type": "jsonb"
  },
  {
    "table_name": "Summary",
    "column_name": "createdAt",
    "data_type": "timestamp without time zone"
  },
  {
    "table_name": "Summary",
    "column_name": "updatedAt",
    "data_type": "timestamp without time zone"
  },
  {
    "table_name": "Summary",
    "column_name": "concatenatedCategories",
    "data_type": "text"
  }
]

And to get info about the index I run:

 SELECT i.relname "Table Name",indexrelname "Index Name",
 pg_size_pretty(pg_total_relation_size(relid)) As "Total Size",
 pg_size_pretty(pg_indexes_size(relid)) as "Total Size of all Indexes",
 pg_size_pretty(pg_relation_size(relid)) as "Table Size",
 pg_size_pretty(pg_relation_size(indexrelid)) "Index Size",
 reltuples::bigint "Estimated table row count"
 FROM pg_stat_all_indexes i JOIN pg_class c ON i.relid=c.oid
 WHERE i.relname='Summary';

Which outputs in hetzner:

// In hetzner (own) server
[
  {
    "Table Name": "Summary",
    "Index Name": "Summary_pkey",
    "Total Size": "149 MB",
    "Total Size of all Indexes": "3256 kB",
    "Table Size": "145 MB",
    "Index Size": "3256 kB",
    "Estimated table row count": 147496
  }
]

// In amazon RDS
[
  {
    "Table Name": "Summary",
    "Index Name": "Summary_pkey",
    "Total Size": "146 MB",
    "Total Size of all Indexes": "3256 kB",
    "Table Size": "142 MB",
    "Index Size": "3256 kB",
    "Estimated table row count": 147496
  }
]

In both cases the Summary_pkey is an index on the id of type btree.

Postgresql.conf

This is the config that I have in Hetzner

# -----------------------------
# PostgreSQL configuration file
# -----------------------------
#------------------------------------------------------------------------------
# FILE LOCATIONS
#------------------------------------------------------------------------------

# The default values of these variables are driven from the -D command-line
# option or PGDATA environment variable, represented here as ConfigDir.

data_directory = '/var/lib/postgresql/13/main'      # use data in another directory
                    # (change requires restart)
hba_file = '/etc/postgresql/13/main/pg_hba.conf'    # host-based authentication file
                    # (change requires restart)
ident_file = '/etc/postgresql/13/main/pg_ident.conf'    # ident configuration file
                    # (change requires restart)

# If external_pid_file is not explicitly set, no extra PID file is written.
external_pid_file = '/var/run/postgresql/13-main.pid'           # write an extra PID file
                    # (change requires restart)


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

# - Connection Settings -

#listen_addresses = 'localhost'     # what IP address(es) to listen on;
listen_addresses = '*'
                    # comma-separated list of addresses;
                    # defaults to 'localhost'; use '*' for all
                    # (change requires restart)
port = 5432             # (change requires restart)
max_connections = 100           # (change requires restart)
#superuser_reserved_connections = 3 # (change requires restart)
unix_socket_directories = '/var/run/postgresql' # comma-separated list of directories
                    # (change requires restart)
#unix_socket_group = ''         # (change requires restart)
#unix_socket_permissions = 0777     # begin with 0 to use octal notation
                    # (change requires restart)
#bonjour = off              # advertise server via Bonjour
                    # (change requires restart)
#bonjour_name = ''          # defaults to the computer name
                    # (change requires restart)

# - TCP settings -
# see "man 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
#tcp_user_timeout = 0           # TCP_USER_TIMEOUT, in milliseconds;
                    # 0 selects the system default

# - Authentication -

#authentication_timeout = 1min      # 1s-600s
#password_encryption = md5      # md5 or scram-sha-256
#db_user_namespace = off

# GSSAPI using Kerberos
#krb_server_keyfile = 'FILE:${sysconfdir}/krb5.keytab'
#krb_caseins_users = off

# - SSL -

ssl = on
#ssl_ca_file = ''
ssl_cert_file = '/etc/ssl/certs/ssl-cert-snakeoil.pem'
#ssl_crl_file = ''
ssl_key_file = '/etc/ssl/private/ssl-cert-snakeoil.key'
#ssl_ciphers = 'HIGH:MEDIUM:+3DES:!aNULL' # allowed SSL ciphers
#ssl_prefer_server_ciphers = on
#ssl_ecdh_curve = 'prime256v1'
#ssl_min_protocol_version = 'TLSv1.2'
#ssl_max_protocol_version = ''
#ssl_dh_params_file = ''
#ssl_passphrase_command = ''
#ssl_passphrase_command_supports_reload = off


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

# - Memory -

shared_buffers = 12GB           # 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 = 1GB              # min 64kB
#hash_mem_multiplier = 1.0      # 1-1000.0 multiplier on hash table work_mem
#maintenance_work_mem = 64MB        # min 1MB
#autovacuum_work_mem = -1       # min 1MB, or -1 to use maintenance_work_mem
#logical_decoding_work_mem = 64MB   # min 64kB
#max_stack_depth = 2MB          # min 100kB
#shared_memory_type = mmap      # the default is the first option
                    # supported by the operating system:
                    #   mmap
                    #   sysv
                    #   windows
                    # (change requires restart)
dynamic_shared_memory_type = posix  # the default is the first option
                    # supported by the operating system:
                    #   posix
                    #   sysv
                    #   windows
                    #   mmap
                    # (change requires restart)

# - Disk -

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

# - Kernel Resources -

#max_files_per_process = 1000       # min 64
                    # (change requires restart)

# - Cost-Based Vacuum Delay -

#vacuum_cost_delay = 0          # 0-100 milliseconds (0 disables)
#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        # max buffers written/round, 0 disables
#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
#maintenance_io_concurrency = 10    # 1-1000; 0 disables prefetching
#max_worker_processes = 8       # (change requires restart)
#max_parallel_maintenance_workers = 2   # taken from max_parallel_workers
#max_parallel_workers_per_gather = 2    # taken from max_parallel_workers
#parallel_leader_participation = on
#max_parallel_workers = 8       # maximum number of max_worker_processes that
                    # can be used in parallel operations
#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 = replica            # 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 and FreeBSD)
                    #   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_init_zero = on         # zero-fill new WAL files
#wal_recycle = on           # recycle WAL files
#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
#wal_skip_threshold = 2MB

#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

# - Archive Recovery -

# These are only used in recovery mode.

#restore_command = ''       # command to use to restore an archived logfile segment
                # placeholders: %p = path of file to restore
                #               %f = file name only
                # e.g. 'cp /mnt/server/archivedir/%f %p'
                # (change requires restart)
#archive_cleanup_command = ''   # command to execute at every restartpoint
#recovery_end_command = ''  # command to execute at completion of recovery

# - Recovery Target -

# Set these only when performing a targeted recovery.

#recovery_target = ''       # 'immediate' to end recovery as soon as a
                                # consistent state is reached
                # (change requires restart)
#recovery_target_name = ''  # the named restore point to which recovery will proceed
                # (change requires restart)
#recovery_target_time = ''  # the time stamp up to which recovery will proceed
                # (change requires restart)
#recovery_target_xid = ''   # the transaction ID up to which recovery will proceed
                # (change requires restart)
#recovery_target_lsn = ''   # the WAL LSN up to which recovery will proceed
                # (change requires restart)
#recovery_target_inclusive = on # Specifies whether to stop:
                # just after the specified recovery target (on)
                # just before the recovery target (off)
                # (change requires restart)
#recovery_target_timeline = 'latest'    # 'current', 'latest', or timeline ID
                # (change requires restart)
#recovery_target_action = 'pause'   # 'pause', 'promote', 'shutdown'
                # (change requires restart)


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

# - Sending Servers -

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

#max_wal_senders = 10       # max number of walsender processes
                # (change requires restart)
#wal_keep_size = 0      # in megabytes; 0 disables
#max_slot_wal_keep_size = -1    # in megabytes; -1 disables
#wal_sender_timeout = 60s   # in milliseconds; 0 disables

#max_replication_slots = 10 # 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
                # method to choose sync standbys, 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.

#primary_conninfo = ''          # connection string to sending server
#primary_slot_name = ''         # replication slot on sending server
#promote_trigger_file = ''      # file name whose presence ends recovery
#hot_standby = on           # "off" disallows 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_create_temp_slot = off    # create temp slot if primary_slot_name
                    # is not set
#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
#recovery_min_apply_delay = 0       # minimum delay for applying changes during recovery

# - Subscribers -

# These settings are ignored on a publisher.

#max_logical_replication_workers = 4    # taken from max_worker_processes
                    # (change requires restart)
#max_sync_workers_per_subscription = 2  # taken from max_logical_replication_workers


#------------------------------------------------------------------------------
# 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_parallel_append = on
#enable_seqscan = on
#enable_sort = on
#enable_incremental_sort = on
#enable_tidscan = on
#enable_partitionwise_join = off
#enable_partitionwise_aggregate = off
#enable_parallel_hash = on
#enable_partition_pruning = 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

#jit_above_cost = 100000        # perform JIT compilation if available
                    # and query more expensive than this;
                    # -1 disables
#jit_inline_above_cost = 500000     # inline small functions if query is
                    # more expensive than this; -1 disables
#jit_optimize_above_cost = 500000   # use expensive JIT optimizations if
                    # query is more expensive than this;
                    # -1 disables

#min_parallel_table_scan_size = 8MB
#min_parallel_index_scan_size = 512kB
#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
#jit = on               # allow JIT compilation
#plan_cache_mode = auto         # auto, force_generic_plan or
                    # force_custom_plan


#------------------------------------------------------------------------------
# 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 = off        # 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 = '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_file_mode = 0600           # creation mode for log files,
                    # begin with 0 to use octal notation
#log_truncate_on_rotation = off     # 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 = 10MB       # 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 -

#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

#log_min_duration_sample = -1       # -1 is disabled, 0 logs a sample of statements
                    # and their durations, > 0 logs only a sample of
                    # statements running at least this number
                    # of milliseconds;
                    # sample fraction is determined by log_statement_sample_rate

#log_statement_sample_rate = 1.0    # fraction of logged statements exceeding
                    # log_min_duration_sample to be logged;
                    # 1.0 logs all such statements, 0.0 never logs


#log_transaction_sample_rate = 0.0  # fraction of transactions whose statements
                    # are logged regardless of their duration; 1.0 logs all
                    # statements from all transactions, 0.0 never logs

# - 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 [%p] %q%u@%d '        # special values:
                    #   %a = application name
                    #   %u = user name
                    #   %d = database name
                    #   %r = remote host and port
                    #   %h = remote host
                    #   %b = backend type
                    #   %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_parameter_max_length = -1      # when logging statements, limit logged
                    # bind-parameter values to N bytes;
                    # -1 means print in full, 0 disables
#log_parameter_max_length_on_error = 0  # when logging an error, limit logged
                    # bind-parameter values to N bytes;
                    # -1 means print in full, 0 disables
#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 = 'Europe/Berlin'

#------------------------------------------------------------------------------
# PROCESS TITLE
#------------------------------------------------------------------------------

cluster_name = '13/main'            # added to process titles if nonempty
                    # (change requires restart)
#update_process_title = on


#------------------------------------------------------------------------------
# STATISTICS
#------------------------------------------------------------------------------

# - Query and 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 = '/var/run/postgresql/13-main.pg_stat_tmp'


# - 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 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_vacuum_insert_threshold = 1000  # min number of row inserts
                    # before vacuum; -1 disables insert
                    # vacuums
#autovacuum_analyze_threshold = 50  # min number of row updates before
                    # analyze
#autovacuum_vacuum_scale_factor = 0.2   # fraction of table size before vacuum
#autovacuum_vacuum_insert_scale_factor = 0.2    # fraction of inserts over table
                    # size before insert 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 = 2ms # 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 -

#client_min_messages = notice       # values in order of decreasing detail:
                    #   debug5
                    #   debug4
                    #   debug3
                    #   debug2
                    #   debug1
                    #   log
                    #   notice
                    #   warning
                    #   error
#search_path = '"$user", public'    # schema names
#row_security = on
#default_tablespace = ''        # a tablespace name, '' uses the default
#temp_tablespaces = ''          # a list of tablespace names, '' uses
                    # only default tablespace
#default_table_access_method = 'heap'
#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
#vacuum_cleanup_index_scale_factor = 0.1    # fraction of total number of tuples
                        # before index cleanup, 0 always performs
                        # index cleanup
#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 = 'Europe/Berlin'
#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 = 1         # min -15, max 3; any value >0 actually
                    # selects precise output mode
#client_encoding = sql_ascii        # actually, defaults to database
                    # encoding

I've truncated it, because StackExchange has a limit on question length, but it is basically the default config, except for shared_buffers and work_mem

Possible clue

One thing that I noticed is the difference in heap fetches: I do a simple query like

explain ANALYSE SELECT id FROM "public"."Summary" WHERE "public"."Summary"."id" IN (67521,67522,67523,...);

with 489 numbers in the IN clause.

In amazon RDS the output is

Index Only Scan using "Summary_pkey" on "Summary"  (cost=0.42..1455.37 rows=489 width=4) (actual time=0.027..0.592 rows=489 loops=1)
  Index Cond: (id = ANY ('{67521,67522,67523,67524,...}'::integer[]))
  Heap Fetches: 0
Planning Time: 0.275 ms
Execution Time: 0.627 ms

While in Hetzner I get

Index Only Scan using "Summary_pkey" on "Summary"  (cost=0.42..1546.87 rows=489 width=4) (actual time=0.068..2.452 rows=489 loops=1)
 Index Cond: (id = ANY ('{67521,67522,67523,...}')
  Heap Fetches: 489
Planning Time: 0.714 ms
Execution Time: 2.538 ms

As you can see the execution time is like 4X

Possible clue number 2

I don't know if it helps, but I migrated the data from RDS to Hetzner doing a pg_dump, and I restored it using psql (no pg_restore) because the dump was in plain text.

Server info

The server is pretty beefy. Here's the info from the hetzner server

$ lscpu

Architecture:        x86_64
CPU op-mode(s):      32-bit, 64-bit
Byte Order:          Little Endian
CPU(s):              8
On-line CPU(s) list: 0-7
Thread(s) per core:  2
Core(s) per socket:  4
Socket(s):           1
NUMA node(s):        1
Vendor ID:           GenuineIntel
CPU family:          6
Model:               158
Model name:          Intel(R) Xeon(R) CPU E3-1275 v6 @ 3.80GHz
Stepping:            9
CPU MHz:             800.395
CPU max MHz:         4200.0000
CPU min MHz:         800.0000
BogoMIPS:            7599.80
Virtualization:      VT-x
L1d cache:           32K
L1i cache:           32K
L2 cache:            256K
L3 cache:            8192K
NUMA node0 CPU(s):   0-7
grep MemTotal /proc/meminfo

MemTotal:       65748320 kB

Things that I've already tried

I'm not a very experienced dba. So the only settings that I tried modifying where the

  • shared_buffers that I changed from 128MB to 12 GB (close to 25% percent of total RAM as of what I've read it's recommended)

  • work_mem where I've set it to 1GB

I also tried running VACCUMM FULL "Summary" but it didn't change anything since in both (rds and hetzner) the number of dead tuples for the "Summary" table is 0.

UPDATE

I've run VACUUM (VERBOSE, ANALYZE) "Summary"; and now the Hetzner table shows 0 heap fetches. But the query it's still taking

Planning Time: 0.720 ms
Execution Time: 2.130 ms

Whereas the RDS takes

Planning Time: 0.559 ms
Execution Time: 0.615 ms
1
  • It is surprising that getting rid of heap fetches made so little difference. I'd look at the hardware, in particular why is it running at less than a quarter of the nominal speed? CPU MHz: 800.395
    – jjanes
    May 3 at 20:01

1 Answer 1

2

Looks like the visibility map gets out of date quickly, requiring the engine to visit data pages even during the index-only scan to confirm visibility of each row. May be you need to make autovacuum more aggressive, if the table is being actively modified.

2
  • That must be the cause. A possible explanation for the different behavior could be that the fast database has PostgreSQL version 13 or better, while the slow database has an older versions. From PostgreSQL v13 on, autovacuum is also triggered by inserts, for exactly the reason to speed up index-only scans. May 3 at 14:04
  • Hey, thanks for commenting. I'm running PostgreSQL 13 on Hetzner
    – Michael
    May 3 at 14:25

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.