On Sun, Sep 27, 2009 at 1:03 AM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Xia Qingran <qingran.xia@xxxxxxxxx> writes: >> I have a big performance problem in my SQL select query: >> select * from event where user_id in >> (500,499,498, ... ,1,0); >> The above SELECT always spends 1200ms. > > Your EXPLAIN ANALYZE shows that the actual runtime is only about 240ms. > So either the planning time is about 1000ms, or transmitting and > displaying the 134K rows produced by the query takes that long, or some > combination of the two. I wouldn't be too surprised if it's the data > display that's slow; but if it's the planning time that you're unhappy > about, updating to a more recent PG release might possibly help. What > version is this anyway? > > regards, tom lane Oh, It is a problem. Forgot to talk about my platform. I am running PostgreSQL 8.4.0 on FreeBSD 7.2-amd64 box, which has dual Xeon 5410 CPUs, 8GB memory and 2 SATA disks. And my postgresql.conf is listed as follow: --------------------------------------------------------------------------------------- listen_addresses = '*' # what IP address(es) to listen on; port = 5432 # (change requires restart) max_connections = 88 # (change requires restart) superuser_reserved_connections = 3 ssl = off # (change requires restart) tcp_keepalives_idle = 0 # TCP_KEEPIDLE, in seconds; tcp_keepalives_interval = 0 # TCP_KEEPINTVL, in seconds; tcp_keepalives_count = 0 # TCP_KEEPCNT; shared_buffers = 2048MB # min 128kB or max_connections*16kB temp_buffers = 32MB # min 800kB max_prepared_transactions = 150 # can be 0 or more, 0 to shutdown the prepared transactions. work_mem = 8MB # min 64kB maintenance_work_mem = 1024MB # min 1MB max_stack_depth = 8MB # min 100kB max_files_per_process = 16384 # min 25 vacuum_cost_delay = 100 # 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 = 500 # 1-10000 credits bgwriter_delay = 500ms # 10-10000ms between rounds bgwriter_lru_maxpages = 100 # 0-1000 max buffers written/round bgwriter_lru_multiplier = 2.0 # 0-10.0 multipler on buffers scanned/round fsync = off # turns forced synchronization on or off synchronous_commit = off # immediate fsync at commit wal_sync_method = fsync # the default is the first option full_page_writes = off # recover from partial page writes wal_buffers = 2MB # min 32kB wal_writer_delay = 200ms # 1-10000 milliseconds commit_delay = 50 # range 0-100000, in microseconds commit_siblings = 5 # range 1-1000 checkpoint_segments = 32 # in logfile segments, min 1, 16MB each checkpoint_timeout = 6min # range 30s-1h checkpoint_completion_target = 0.5 # checkpoint target duration, 0.0 - 1.0 checkpoint_warning = 30s # 0 is off 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 seq_page_cost = 1.8 # measured on an arbitrary scale random_page_cost = 2 # same scale as above cpu_tuple_cost = 0.15 # same scale as above cpu_index_tuple_cost = 0.07 # same scale as above cpu_operator_cost = 0.03 # same scale as above effective_cache_size = 3072MB geqo = on geqo_threshold = 20 geqo_effort = 7 # 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 default_statistics_target = 500 # range 1-1000 constraint_exclusion = partition from_collapse_limit = 20 join_collapse_limit = 20 # 1 disables collapsing of explicit log_destination = 'syslog' syslog_facility = 'LOCAL2' syslog_ident = 'postgres' client_min_messages = notice # values in order of decreasing detail: log_min_messages = error # values in order of decreasing detail: log_error_verbosity = terse # terse, default, or verbose messages log_min_error_statement = panic # values in order of decreasing detail: log_min_duration_statement = -1 # -1 is disabled, 0 logs all statements silent_mode = on debug_print_parse = off debug_print_rewritten = off debug_print_plan = off debug_pretty_print = off log_checkpoints = off log_connections = off log_disconnections = off log_duration = on log_hostname = off log_line_prefix = '' # special values: log_lock_waits = off # log lock waits >= deadlock_timeout log_statement = 'none' # none, ddl, mod, all log_temp_files = -1 # log temporary files equal or larger track_activities = on track_counts = on update_process_title = off log_parser_stats = off log_planner_stats = off log_executor_stats = off log_statement_stats = off autovacuum = on # Enable autovacuum subprocess? 'on' log_autovacuum_min_duration = 10 # -1 disables, 0 logs all actions and autovacuum_max_workers = 3 # max number of autovacuum subprocesses autovacuum_naptime = 10min # time between autovacuum runs autovacuum_vacuum_threshold = 100 # min number of row updates before autovacuum_analyze_threshold = 50 # min number of row updates before 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 autovacuum_vacuum_cost_delay = 30 # default vacuum cost delay for autovacuum_vacuum_cost_limit = 200 # default vacuum cost limit for datestyle = 'iso, mdy' client_encoding = utf-8 # actually, defaults to database lc_messages = 'C' # locale for system error message lc_monetary = 'C' # locale for monetary formatting lc_numeric = 'C' # locale for number formatting lc_time = 'C' # locale for time formatting default_text_search_config = 'pg_catalog.english' deadlock_timeout = 60s max_locks_per_transaction = 32 # min 10 regex_flavor = basic # advanced, extended, or basic --------------------------------------------------------------------------------------- Thanks a lot. -- 夏清然 Xia Qingran qingran.xia@xxxxxxxxx Sent from Beijing, 11, China Joan Crawford - "I, Joan Crawford, I believe in the dollar. Everything I earn, I spend." - http://www.brainyquote.com/quotes/authors/j/joan_crawford.html -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
