I have a PostgreSQL table of point locations that contains 9.5 million rows. I am attempting to run this query:
/geoserver/workspace/ows?service=WFS&version=1.0.0&request=GetFeature&typeName=workspace:layer&maxFeatures=50&outputFormat=application/json but it takes multiple minutes to respond.
When I look at the geoserver logs I see this:
Request: getFeature
service = WFS
version = 1.0.0
baseUrl = http://my_geoserver_url/geoserver/
query[0]:
typeName[0] = {workspace}layer
maxFeatures = 50
outputFormat = application/json
resultType = results
19 Nov 15:26:04 INFO [wfs.json] - about to encode JSON
At that point it stalls for many minutes.
When I look at the currently active queries of my PostgreSQL server I see this:
SELECT count(*) FROM "public"."layer"
This query by itself takes 335 seconds to return a response. First of all, wtf? Even if it has to count row by row, 9.5 million isn't THAT many rows. Is there any way to speed up this operation?
Second, why is it trying to do SELECT count(*) FROM "public"."layer" and is there any way to prevent it? I specified maxFeatures = 50, so why count them?
Version: PostgreSQL 11.2 (Debian 11.2-1.pgdg90+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516, 64-bi
Machine: n1-standard-2 (2 vCPUs, 7.5 GB memory) (from Google Cloud)
Variables:
allow_system_table_mods off
application_name Navicat
archive_command (disabled)
archive_mode off
archive_timeout 0
array_nulls on
authentication_timeout 60
autovacuum on
autovacuum_analyze_scale_factor 0.1
autovacuum_analyze_threshold 50
autovacuum_freeze_max_age 200000000
autovacuum_max_workers 3
autovacuum_multixact_freeze_max_age 400000000
autovacuum_naptime 60
autovacuum_vacuum_cost_delay 20
autovacuum_vacuum_cost_limit -1
autovacuum_vacuum_scale_factor 0.2
autovacuum_vacuum_threshold 50
autovacuum_work_mem -1
backend_flush_after 0
backslash_quote safe_encoding
bgwriter_delay 200
bgwriter_flush_after 64
bgwriter_lru_maxpages 100
bgwriter_lru_multiplier 2
block_size 8192
bonjour off
bonjour_name
bytea_output hex
check_function_bodies on
checkpoint_completion_target 0.5
checkpoint_flush_after 32
checkpoint_timeout 300
checkpoint_warning 30
client_encoding UNICODE
client_min_messages notice
cluster_name
commit_delay 0
commit_siblings 5
config_file /var/lib/postgresql/data/postgresql.conf
constraint_exclusion partition
cpu_index_tuple_cost 0.005
cpu_operator_cost 0.0025
cpu_tuple_cost 0.01
cursor_tuple_fraction 0.1
data_checksums off
data_directory /var/lib/postgresql/data
data_directory_mode 0700
data_sync_retry off
DateStyle ISO, MDY
db_user_namespace off
deadlock_timeout 1000
debug_assertions off
debug_pretty_print on
debug_print_parse off
debug_print_plan off
debug_print_rewritten off
default_statistics_target 100
default_tablespace
default_text_search_config pg_catalog.english
default_transaction_deferrable off
default_transaction_isolation read committed
default_transaction_read_only off
default_with_oids off
dynamic_library_path $libdir
dynamic_shared_memory_type posix
effective_cache_size 524288
effective_io_concurrency 1
enable_bitmapscan on
enable_gathermerge on
enable_hashagg on
enable_hashjoin on
enable_indexonlyscan on
enable_indexscan on
enable_material on
enable_mergejoin on
enable_nestloop on
enable_parallel_append on
enable_parallel_hash on
enable_partition_pruning on
enable_partitionwise_aggregate off
enable_partitionwise_join off
enable_seqscan on
enable_sort on
enable_tidscan on
escape_string_warning on
event_source PostgreSQL
exit_on_error off
external_pid_file
extra_float_digits 0
force_parallel_mode off
from_collapse_limit 8
fsync on
full_page_writes on
geqo on
geqo_effort 5
geqo_generations 0
geqo_pool_size 0
geqo_seed 0
geqo_selection_bias 2
geqo_threshold 12
gin_fuzzy_search_limit 0
gin_pending_list_limit 4096
hba_file /var/lib/postgresql/data/pg_hba.conf
hot_standby on
hot_standby_feedback off
huge_pages try
ident_file /var/lib/postgresql/data/pg_ident.conf
idle_in_transaction_session_timeout 0
ignore_checksum_failure off
ignore_system_indexes off
integer_datetimes on
IntervalStyle postgres
jit off
jit_above_cost 100000
jit_debugging_support off
jit_dump_bitcode off
jit_expressions on
jit_inline_above_cost 500000
jit_optimize_above_cost 500000
jit_profiling_support off
jit_provider llvmjit
jit_tuple_deforming on
join_collapse_limit 8
krb_caseins_users off
krb_server_keyfile FILE:/etc/postgresql-common/krb5.keytab
lc_collate en_US.utf8
lc_ctype en_US.utf8
lc_messages en_US.utf8
lc_monetary en_US.utf8
lc_numeric en_US.utf8
lc_time en_US.utf8
listen_addresses *
lo_compat_privileges off
local_preload_libraries
lock_timeout 0
log_autovacuum_min_duration -1
log_checkpoints off
log_connections off
log_destination stderr
log_directory log
log_disconnections off
log_duration off
log_error_verbosity default
log_executor_stats off
log_file_mode 0600
log_filename postgresql-%Y-%m-%d_%H%M%S.log
log_hostname off
log_line_prefix %m [%p]
log_lock_waits off
log_min_duration_statement -1
log_min_error_statement error
log_min_messages warning
log_parser_stats off
log_planner_stats off
log_replication_commands off
log_rotation_age 1440
log_rotation_size 10240
log_statement none
log_statement_stats off
log_temp_files -1
log_timezone UTC
log_truncate_on_rotation off
logging_collector off
maintenance_work_mem 65536
max_connections 100
max_files_per_process 1000
max_function_args 100
max_identifier_length 63
max_index_keys 32
max_locks_per_transaction 64
max_logical_replication_workers 4
max_parallel_maintenance_workers 2
max_parallel_workers 8
max_parallel_workers_per_gather 2
max_pred_locks_per_page 2
max_pred_locks_per_relation -2
max_pred_locks_per_transaction 64
max_prepared_transactions 0
max_replication_slots 10
max_stack_depth 2048
max_standby_archive_delay 30000
max_standby_streaming_delay 30000
max_sync_workers_per_subscription 2
max_wal_senders 10
max_wal_size 1024
max_worker_processes 8
min_parallel_index_scan_size 64
min_parallel_table_scan_size 1024
min_wal_size 80
old_snapshot_threshold -1
operator_precedence_warning off
parallel_leader_participation on
parallel_setup_cost 1000
parallel_tuple_cost 0.1
password_encryption md5
port 5432
post_auth_delay 0
postgis.backend geos
pre_auth_delay 0
quote_all_identifiers off
random_page_cost 4
restart_after_crash on
row_security on
search_path public, "$user", public
segment_size 131072
seq_page_cost 1
server_encoding UTF8
server_version 11.2 (Debian 11.2-1.pgdg90+1)
server_version_num 110002
session_preload_libraries
session_replication_role origin
shared_buffers 16384
shared_preload_libraries
ssl off
ssl_ca_file
ssl_cert_file server.crt
ssl_ciphers HIGH:MEDIUM:+3DES:!aNULL
ssl_crl_file
ssl_dh_params_file
ssl_ecdh_curve prime256v1
ssl_key_file server.key
ssl_passphrase_command
ssl_passphrase_command_supports_reload off
ssl_prefer_server_ciphers on
standard_conforming_strings on
statement_timeout 0
stats_temp_directory pg_stat_tmp
superuser_reserved_connections 3
synchronize_seqscans on
synchronous_commit on
synchronous_standby_names
syslog_facility local0
syslog_ident postgres
syslog_sequence_numbers on
syslog_split_messages on
tcp_keepalives_count 9
tcp_keepalives_idle 7200
tcp_keepalives_interval 75
temp_buffers 1024
temp_file_limit -1
temp_tablespaces
TimeZone UTC
timezone_abbreviations Default
trace_notify off
trace_recovery_messages log
trace_sort off
track_activities on
track_activity_query_size 1024
track_commit_timestamp off
track_counts on
track_functions none
track_io_timing off
transaction_deferrable off
transaction_isolation read committed
transaction_read_only off
transform_null_equals off
unix_socket_directories /var/run/postgresql
unix_socket_group
unix_socket_permissions 0777
update_process_title on
vacuum_cleanup_index_scale_factor 0.1
vacuum_cost_delay 0
vacuum_cost_limit 200
vacuum_cost_page_dirty 20
vacuum_cost_page_hit 1
vacuum_cost_page_miss 10
vacuum_defer_cleanup_age 0
vacuum_freeze_min_age 50000000
vacuum_freeze_table_age 150000000
vacuum_multixact_freeze_min_age 5000000
vacuum_multixact_freeze_table_age 150000000
wal_block_size 8192
wal_buffers 512
wal_compression off
wal_consistency_checking
wal_keep_segments 0
wal_level replica
wal_log_hints off
wal_receiver_status_interval 10
wal_receiver_timeout 60000
wal_retrieve_retry_interval 5000
wal_segment_size 16777216
wal_sender_timeout 60000
wal_sync_method fdatasync
wal_writer_delay 200
wal_writer_flush_after 128
work_mem 4096
xmlbinary base64
xmloption content
zero_damaged_pages off
explain (analyze, buffers, format text):
Buffers: shared hit=2940 read=1601607
-> Gather (cost=1655905.64..1655905.85 rows=2 width=8) (actual time=191335.534..191349.259 rows=3 loops=1)
Workers Planned: 2
Workers Launched: 2
Buffers: shared hit=2940 read=1601607
-> Partial Aggregate (cost=1654905.64..1654905.65 rows=1 width=8) (actual time=191277.227..191277.227 rows=1 loops=3)
Buffers: shared hit=2940 read=1601607
-> Parallel Seq Scan on forecast (cost=0.00..1644833.91 rows=4028691 width=0) (actual time=8.037..190681.354 rows=3222220 loops=3)
Buffers: shared hit=2940 read=1601607
Planning Time: 0.351 ms
Execution Time: 191349.424 ms
Indexes:
CREATE INDEX forecast_init_utc ON public.forecast USING btree (forecast_init_utc)
CREATE UNIQUE INDEX forecast_pkey ON public.forecast USING btree (ogc_fid)
CREATE INDEX forecast_wkb_geometry_geom_idx ON public.forecast USING gist (wkb_geometry)
CREATE INDEX forecast_init_local ON public.forecast USING btree (forecast_init_local)
CREATE INDEX country_code ON public.forecast USING btree (country_code)
CREATE INDEX store_num ON public.forecast USING btree (store_num)
Edit: It appears that VACUUM ANALYZE did the trick. It took 728 seconds to run, but now the query returns quickly. How often do I need to run that?
Here is the new explain (analyze, buffers, format text):
Finalize Aggregate (cost=204220.77..204220.78 rows=1 width=8) (actual time=7116.754..7116.755 rows=1 loops=1)
Buffers: shared hit=525705 read=25977
-> Gather (cost=204220.55..204220.77 rows=2 width=8) (actual time=7115.613..7123.979 rows=3 loops=1)
Workers Planned: 2
Workers Launched: 2
Buffers: shared hit=525705 read=25977
-> Partial Aggregate (cost=203220.55..203220.57 rows=1 width=8) (actual time=7051.177..7051.178 rows=1 loops=3)
Buffers: shared hit=525705 read=25977
-> Parallel Index Only Scan using store_num on forecast (cost=0.43..193125.85 rows=4037882 width=0) (actual time=18.684..6564.663 rows=3229577 loops=3)
Heap Fetches: 0
Buffers: shared hit=525705 read=25977
Planning Time: 0.896 ms
Execution Time: 7124.113 ms
