The System Catalogs of PostgreSQL
scott=# dS
List of relations
Schema | Name | Type | Owner
------------+---------------------------------+----------+----------
pg_catalog | pg_aggregate | table | postgres
pg_catalog | pg_am | table | postgres
pg_catalog | pg_amop | table | postgres
pg_catalog | pg_amproc | table | postgres
pg_catalog | pg_attrdef | table | postgres
pg_catalog | pg_attribute | table | postgres
pg_catalog | pg_auth_members | table | postgres
pg_catalog | pg_authid | table | postgres
pg_catalog | pg_available_extension_versions | view | postgres
pg_catalog | pg_available_extensions | view | postgres
pg_catalog | pg_cast | table | postgres
pg_catalog | pg_class | table | postgres
pg_catalog | pg_collation | table | postgres
pg_catalog | pg_constraint | table | postgres
pg_catalog | pg_conversion | table | postgres
pg_catalog | pg_cursors | view | postgres
pg_catalog | pg_database | table | postgres
pg_catalog | pg_db_role_setting | table | postgres
pg_catalog | pg_default_acl | table | postgres
pg_catalog | pg_depend | table | postgres
pg_catalog | pg_description | table | postgres
pg_catalog | pg_enum | table | postgres
pg_catalog | pg_event_trigger | table | postgres
pg_catalog | pg_extension | table | postgres
pg_catalog | pg_file_settings | view | postgres
pg_catalog | pg_foreign_data_wrapper | table | postgres
pg_catalog | pg_foreign_server | table | postgres
pg_catalog | pg_foreign_table | table | postgres
pg_catalog | pg_group | view | postgres
pg_catalog | pg_index | table | postgres
pg_catalog | pg_indexes | view | postgres
pg_catalog | pg_inherits | table | postgres
pg_catalog | pg_language | table | postgres
pg_catalog | pg_largeobject | table | postgres
pg_catalog | pg_largeobject_metadata | table | postgres
pg_catalog | pg_locks | view | postgres
pg_catalog | pg_matviews | view | postgres
pg_catalog | pg_namespace | table | postgres
pg_catalog | pg_opclass | table | postgres
pg_catalog | pg_operator | table | postgres
pg_catalog | pg_opfamily | table | postgres
pg_catalog | pg_pltemplate | table | postgres
pg_catalog | pg_policies | view | postgres
pg_catalog | pg_policy | table | postgres
pg_catalog | pg_prepared_statements | view | postgres
pg_catalog | pg_prepared_xacts | view | postgres
pg_catalog | pg_proc | table | postgres
pg_catalog | pg_range | table | postgres
pg_catalog | pg_replication_origin | table | postgres
pg_catalog | pg_replication_origin_status | view | postgres
pg_catalog | pg_replication_slots | view | postgres
pg_catalog | pg_rewrite | table | postgres
pg_catalog | pg_roles | view | postgres
pg_catalog | pg_rules | view | postgres
pg_catalog | pg_seclabel | table | postgres
pg_catalog | pg_seclabels | view | postgres
pg_catalog | pg_settings | view | postgres
pg_catalog | pg_shadow | view | postgres
pg_catalog | pg_shdepend | table | postgres
pg_catalog | pg_shdescription | table | postgres
pg_catalog | pg_shseclabel | table | postgres
pg_catalog | pg_stat_activity | view | postgres
pg_catalog | pg_stat_all_indexes | view | postgres
pg_catalog | pg_stat_all_tables | view | postgres
pg_catalog | pg_stat_archiver | view | postgres
pg_catalog | pg_stat_bgwriter | view | postgres
pg_catalog | pg_stat_database | view | postgres
pg_catalog | pg_stat_database_conflicts | view | postgres
pg_catalog | pg_stat_replication | view | postgres
pg_catalog | pg_stat_ssl | view | postgres
pg_catalog | pg_stat_sys_indexes | view | postgres
pg_catalog | pg_stat_sys_tables | view | postgres
pg_catalog | pg_stat_user_functions | view | postgres
pg_catalog | pg_stat_user_indexes | view | postgres
pg_catalog | pg_stat_user_tables | view | postgres
pg_catalog | pg_stat_xact_all_tables | view | postgres
pg_catalog | pg_stat_xact_sys_tables | view | postgres
pg_catalog | pg_stat_xact_user_functions | view | postgres
pg_catalog | pg_stat_xact_user_tables | view | postgres
pg_catalog | pg_statio_all_indexes | view | postgres
pg_catalog | pg_statio_all_sequences | view | postgres
pg_catalog | pg_statio_all_tables | view | postgres
pg_catalog | pg_statio_sys_indexes | view | postgres
pg_catalog | pg_statio_sys_sequences | view | postgres
pg_catalog | pg_statio_sys_tables | view | postgres
pg_catalog | pg_statio_user_indexes | view | postgres
pg_catalog | pg_statio_user_sequences | view | postgres
pg_catalog | pg_statio_user_tables | view | postgres
pg_catalog | pg_statistic | table | postgres
pg_catalog | pg_stats | view | postgres
pg_catalog | pg_tables | view | postgres
pg_catalog | pg_tablespace | table | postgres
pg_catalog | pg_timezone_abbrevs | view | postgres
pg_catalog | pg_timezone_names | view | postgres
pg_catalog | pg_transform | table | postgres
pg_catalog | pg_trigger | table | postgres
pg_catalog | pg_ts_config | table | postgres
pg_catalog | pg_ts_config_map | table | postgres
pg_catalog | pg_ts_dict | table | postgres
pg_catalog | pg_ts_parser | table | postgres
pg_catalog | pg_ts_template | table | postgres
pg_catalog | pg_type | table | postgres
pg_catalog | pg_user | view | postgres
pg_catalog | pg_user_mapping | table | postgres
pg_catalog | pg_user_mappings | view | postgres
pg_catalog | pg_views | view | postgres
public | pgstatspack_bgwriter | table | postgres
public | pgstatspack_database | table | postgres
public | pgstatspack_database_v | view | postgres
public | pgstatspack_functions | table | postgres
public | pgstatspack_functions_v | view | postgres
public | pgstatspack_indexes | table | postgres
public | pgstatspack_indexes_v | view | postgres
public | pgstatspack_names | table | postgres
public | pgstatspack_sequences | table | postgres
public | pgstatspack_sequences_v | view | postgres
public | pgstatspack_settings | table | postgres
public | pgstatspack_settings_v | view | postgres
public | pgstatspack_snap | table | postgres
public | pgstatspack_statements | table | postgres
public | pgstatspack_statements_v | view | postgres
public | pgstatspack_tables | table | postgres
public | pgstatspack_tables_v | view | postgres
public | pgstatspack_version | table | postgres
public | pgstatspackid | sequence | postgres
public | pgstatspacknameid | sequence | postgres
scott | bonus | table | scott
scott | dept | table | scott
scott | emp | table | scott
scott | salgrade | table | scott
(130 rows)
PG(>=9.4) look archive status;
postgres=# select * from pg_stat_archiver;
-[ RECORD 1 ]------+------------------------------
archived_count | 10
last_archived_wal | 000000010000000000000009
last_archived_time | 2016-05-03 23:12:57.436303-07
failed_count | 0
last_failed_wal |
last_failed_time |
stats_reset | 2016-04-25 20:26:55.013401-07
PG check Master-Slave lag time:
master monitor
postgres=# select
postgres-# pid, client_addr,
postgres-# pg_size_pretty(pg_xlog_location_diff(pg_current_xlog_location(),sent_location)) as
postgres-# pending_xlog,
postgres-# pg_size_pretty(pg_xlog_location_diff(sent_location,write_location)) as write,
postgres-# pg_size_pretty(pg_xlog_location_diff(write_location,flush_location)) as flush,
postgres-# pg_size_pretty(pg_xlog_location_diff(flush_location,replay_location)) as replay,
postgres-# pg_size_pretty(pg_xlog_location_diff(pg_current_xlog_location(),replay_location)) as
postgres-# total_lag
postgres-# from pg_stat_replication;
pid | client_addr | pending_xlog | write | flush | replay | total_lag
-------+-----------------+--------------+---------+---------+---------+-----------
20608 | 192.168.230.129 | 0 bytes | 0 bytes | 0 bytes | 0 bytes | 0 bytes
(1 row)
standby
pg_current_xlog_location() - pg_last_xlog_receive_location();
PG processer:
[root@localhost data]# ps auxf|grep postgres
root 4575 0.0 0.1 5028 1284 pts/2 S 18:42 0:00 | \_ su - postgres
postgres 4579 0.0 0.1 4764 1516 pts/2 S 18:42 0:00 | \_ -bash
postgres 20619 0.0 0.1 5252 1612 pts/2 S+ 19:56 0:00 | \_ ./psql -h localhost -p 5432 -U postgres
root 21345 0.0 0.0 4028 656 pts/3 S+ 20:30 0:00 \_ grep postgres
postgres 4737 0.0 1.7 164472 18564 pts/2 S 18:48 0:00 /usr/local/pg952/bin/postgres -D ../data
postgres 4738 0.0 0.0 9984 796 ? Ss 18:48 0:00 \_ postgres: logger process
postgres 4740 0.0 0.2 164604 2348 ? Ss 18:48 0:00 \_ postgres: checkpointer process
postgres 4741 0.0 0.1 164604 2056 ? Ss 18:48 0:00 \_ postgres: writer process
postgres 4742 0.0 0.4 164472 5140 ? Ss 18:48 0:00 \_ postgres: wal writer process
postgres 4743 0.0 0.1 165004 1752 ? Ss 18:48 0:00 \_ postgres: autovacuum launcher process
postgres 4744 0.0 0.0 10024 732 ? Ss 18:48 0:00 \_ postgres: archiver process
postgres 4745 0.0 0.0 10024 916 ? Ss 18:48 0:00 \_ postgres: stats collector process
postgres 20608 0.0 0.2 165284 2288 ? Ss 19:55 0:00 \_ postgres: wal sender process postgres 192.168.230.129(41845) streaming 0/9001100
postgres 20620 0.0 0.5 165820 5360 ? Ss 19:56 0:00 \_ postgres: postgres postgres 127.0.0.1(34950) idle
[postgres@localhost ~]$ ps hf -u postgres -o cmd
-bash
\_ ps hf -u postgres -o cmd
/usr/local/pg952/bin/postgres -D /usr/local/pg952/data
\_ postgres: logger process
\_ postgres: checkpointer process
\_ postgres: writer process
\_ postgres: wal writer process
\_ postgres: autovacuum launcher process
\_ postgres: archiver process last was 000000010000000000000010
\_ postgres: stats collector process
pg_stat_database
postgres=# select * from pg_stat_database where datname = 'postgres';
-[ RECORD 1 ]--+------------------------------
datid | 13157
datname | postgres
numbackends | 1
xact_commit | 1767
xact_rollback | 13
blks_read | 1266
blks_hit | 91553
tup_returned | 851252
tup_fetched | 23028
tup_inserted | 18
tup_updated | 0
tup_deleted | 0
conflicts | 0
temp_files | 0
temp_bytes | 0
deadlocks | 0
blk_read_time | 0
blk_write_time | 0
stats_reset | 2016-04-25 20:27:51.952205-07
Cache hit ratio
blks_read | 1266
blks_hit | 91553
postgres=# select
postgres-# sum(blks_hit)*100/sum(blks_hit+blks_read) as hit_ratio
postgres-# from pg_stat_database;
-[ RECORD 1 ]------------------
hit_ratio | 98.6382557626735794
More is better, and not less than 90%
Anomalies
xact_commit | 1767
xact_rollback | 13
conflicts | 0
temp_files | 0
temp_bytes | 0
deadlocks | 0
postgres=# select
datname,
(xact_commit*100)/(xact_commit+xact_rollback) as c_ratio,
deadlocks, conflicts,
temp_files, pg_size_pretty(temp_bytes) as temp_size
from pg_stat_database;
ERROR: division by zero
Conflicts: pg_stat_database_conflicts, server logs.
Deadlocks: server logs + log_lock_waits.
Temp files: server logs + log_temp_files, pg_stat_statements.
pg_stat_bgwriter
postgres=# select * from pg_stat_bgwriter;
-[ RECORD 1 ]---------+------------------------------
checkpoints_timed | 161
checkpoints_req | 4
checkpoint_write_time | 2140
checkpoint_sync_time | 18
buffers_checkpoint | 23
buffers_clean | 0
maxwritten_clean | 0
buffers_backend | 1
buffers_backend_fsync | 0
buffers_alloc | 1395
stats_reset | 2016-04-25 20:26:55.013401-07
Checkpoints
postgres=# select * from pg_stat_bgwriter;
-[ RECORD 1 ]---------+------------------------------
checkpoints_timed | 161
checkpoints_req | 4
checkpoint_write_time | 2140
checkpoint_sync_time | 18
buffers_checkpoint | 23
buffers_clean | 0
maxwritten_clean | 0
buffers_backend | 1
buffers_backend_fsync | 0
buffers_alloc | 1395
stats_reset | 2016-04-25 20:26:55.013401-07
checkpoints_req > checkpoints_timed = bad
postgresql.conf:
● min_wal_size, max_wal_size (checkpoint_segments, >= 9.4)
● checkpoint_timeout
● checkpoint_completion_target
buffers_clean | 0
maxwritten_clean | 0
buffers_backend_fsync | 0
Clean dirty pages for backends.
Helps checkpointer.
postgresql.conf:
● bgwriter_delay
● bgwriter_lru_maxpages
● bgwriter_lru_multiplier
pg_stat_replication
postgres=# select * from pg_stat_replication;
-[ RECORD 1 ]----+------------------------------
pid | 5101
usesysid | 10
usename | postgres
application_name | walreceiver
client_addr | 192.168.230.129
client_hostname |
client_port | 41419
backend_start | 2016-05-04 19:17:34.515672-07
backend_xmin |
state | streaming
sent_location | 0/110004D0
write_location | 0/110004D0
flush_location | 0/110004D0
replay_location | 0/110004D0
sync_priority | 0
sync_state | async
0/110004D0 — location in transaction log (WAL)
All values are equal = ideal
Replication lag
Lag causes:
Networking
Storage
CPU
How many bytes written in WAL
$ select
pg_xlog_location_diff(pg_current_xlog_location(),'0/00000000');
postgres=# select
postgres-# pg_xlog_location_diff(pg_current_xlog_location(),'0/00000000');
-[ RECORD 1 ]---------+----------
pg_xlog_location_diff | 285214112
Replication lag in bytes
$ select
client_addr,
pg_xlog_location_diff(pg_current_xlog_location(), replay_location)
from pg_stat_replication;
postgres=# select
postgres-# client_addr,
postgres-# pg_xlog_location_diff(pg_current_xlog_location(), replay_location)
postgres-# from pg_stat_replication;
-[ RECORD 1 ]---------+----------------
client_addr | 192.168.230.129
pg_xlog_location_diff | 0
Replication lag in seconds
$ select
extract(epoch from now() - pg_last_xact_replay_timestamp());
postgres=# select
postgres-# extract(epoch from now() - pg_last_xact_replay_timestamp());
-[ RECORD 1 ]
date_part |
Replication lag
postgres=# select
client_addr as client,
pg_size_pretty(pg_xlog_location_diff(pg_current_xlog_location(),sent_location)) as pending,
pg_size_pretty(pg_xlog_location_diff(sent_location,write_location)) as write,
pg_size_pretty(pg_xlog_location_diff(write_location,flush_location)) as flush,
pg_size_pretty(pg_xlog_location_diff(flush_location,replay_location)) as replay,
pg_size_pretty(pg_xlog_location_diff(pg_current_xlog_location(),replay_location)) as total
from pg_stat_replication;
-[ RECORD 1 ]------------
client | 192.168.230.129
pending | 0 bytes
write | 0 bytes
flush | 0 bytes
replay | 0 bytes
total | 0 bytes
pg_stat_all_tables
postgres=# select * from pg_stat_all_tables;
-[ RECORD 1 ]-------+------------------------
relid | 1261
schemaname | pg_catalog
relname | pg_auth_members
seq_scan | 0
seq_tup_read | 0
idx_scan | 0
idx_tup_fetch | 0
n_tup_ins | 0
n_tup_upd | 0
n_tup_del | 0
n_tup_hot_upd | 0
n_live_tup | 0
n_dead_tup | 0
n_mod_since_analyze | 0
last_vacuum |
last_autovacuum |
last_analyze |
last_autoanalyze |
vacuum_count | 0
autovacuum_count | 0
analyze_count | 0
autoanalyze_count | 0
Sequential scans
postgres=# select
postgres-# relname,
postgres-# pg_size_pretty(pg_relation_size(relname::regclass)) as size,
postgres-# seq_scan, seq_tup_read,
postgres-# seq_scan / seq_tup_read as seq_tup_avg
postgres-# from pg_stat_user_tables
postgres-# where seq_tup_read > 0 order by 3,4 desc limit 5;
-[ RECORD 1 ]+-----------
relname | test
size | 8192 bytes
seq_scan | 1
seq_tup_read | 5
seq_tup_avg | 0
Tables size
postgres=# select
postgres-# relname,
postgres-# pg_size_pretty(pg_total_relation_size(relname::regclass)) as
postgres-# full_size,
postgres-# pg_size_pretty(pg_relation_size(relname::regclass)) as
postgres-# table_size,
postgres-# pg_size_pretty(pg_total_relation_size(relname::regclass) -
postgres(# pg_relation_size(relname::regclass)) as index_size
postgres-# from pg_stat_user_tables
postgres-# order by pg_total_relation_size(relname::regclass) desc limit 10;
-[ RECORD 1 ]----------
relname | test
full_size | 8192 bytes
table_size | 8192 bytes
index_size | 0 bytes
postgres=#
postgres=# dt+
List of relations
-[ RECORD 1 ]-----------
Schema | public
Name | test
Type | table
Owner | postgres
Size | 8192 bytes
Description |
Write activity
UPDATE = DELETE + INSERT
UPDATE = TABLE UPDATE + INDEX UPDATE
postgres=# select * from pg_stat_all_tables;
-[ RECORD 1 ]-------+------------------------
relid | 1261
schemaname | pg_catalog
relname | pg_auth_members
seq_scan | 0
seq_tup_read | 0
idx_scan | 0
idx_tup_fetch | 0
n_tup_ins | 0
n_tup_upd | 0
n_tup_del | 0
n_tup_hot_upd | 0
n_live_tup | 0
n_dead_tup | 0
n_mod_since_analyze | 0
last_vacuum |
last_autovacuum |
last_analyze |
last_autoanalyze |
vacuum_count | 0
autovacuum_count | 0
analyze_count | 0
autoanalyze_count | 0
What is Heap-Only Tuples?
HOT does not cause index update.
HOT is only for non-indexed columns.
Big n_tup_hot_upd = good.
How to increase n_tup_hot_upd?
Fillfactor determines page packing ratio (between 10 and 100).
Tables (and indexes) size overhead.
ALTER TABLE table_name SET (fillfactor = 70);
postgres=# select
postgres-# s.relname,
postgres-# pg_size_pretty(pg_relation_size(relid)),
postgres-# coalesce(n_tup_ins,0) + 2 * coalesce(n_tup_upd,0) -
postgres-# coalesce(n_tup_hot_upd,0) + coalesce(n_tup_del,0) AS total_writes,
postgres-# (coalesce(n_tup_hot_upd,0)::float * 100 / (case when n_tup_upd > 0
postgres(# then n_tup_upd else 1 end)::float)::numeric(10,2) AS hot_rate,
postgres-# (select v[1] FROM regexp_matches(reloptions::text,E'fillfactor=(\d+)') as
postgres(# r(v) limit 1) AS fillfactor
postgres-# from pg_stat_all_tables s
postgres-# join pg_class c ON c.oid=relid
postgres-# order by total_writes desc limit 50;
-[ RECORD 1 ]--+------------------------
relname | pg_attribute
pg_size_pretty | 344 kB
total_writes | 7
hot_rate | 0.00
fillfactor |
-[ RECORD 2 ]--+------------------------
relname | test
pg_size_pretty | 8192 bytes
total_writes | 5
hot_rate | 0.00
fillfactor |
-[ RECORD 3 ]--+------------------------
relname | pg_depend
pg_size_pretty | 408 kB
total_writes | 3
hot_rate | 0.00
fillfactor |
-[ RECORD 4 ]--+------------------------
relname | pg_type
pg_size_pretty | 64 kB
total_writes | 2
hot_rate | 0.00
fillfactor |
-[ RECORD 5 ]--+------------------------
relname | pg_class
pg_size_pretty | 104 kB
total_writes | 1
hot_rate | 0.00
fillfactor |
-[ RECORD 6 ]--+------------------------
relname | pg_toast_1255
pg_size_pretty | 0 bytes
total_writes | 0
hot_rate | 0.00
fillfactor |
-[ RECORD 7 ]--+------------------------
relname | pg_toast_2618
pg_size_pretty | 368 kB
total_writes | 0
hot_rate | 0.00
fillfactor |
Autovacuum queue
postgres=# select c.relname,
postgres-# current_setting('autovacuum_vacuum_threshold') as av_base_thresh,
postgres-# current_setting('autovacuum_vacuum_scale_factor') as av_scale_factor,
postgres-# (current_setting('autovacuum_vacuum_threshold')::int +
postgres(# (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)) as
postgres-# av_thresh,
postgres-# s.n_dead_tup
postgres-# from pg_stat_user_tables s join pg_class c ON s.relname = c.relname
postgres-# where s.n_dead_tup > (current_setting('autovacuum_vacuum_threshold')::int
postgres(# + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples));
relname | av_base_thresh | av_scale_factor | av_thresh | n_dead_tup
---------+----------------+-----------------+-----------+------------
(0 rows)
Experience
https://github.com/eshkinkot/avito/blob/master/munin/vacuum_queue
pg_stat_all_indexes
postgres=# select * from pg_stat_all_indexes where idx_scan = 0;
-[ RECORD 1 ]-+-------------------------------------
relid | 2830
indexrelid | 2831
schemaname | pg_toast
relname | pg_toast_2604
indexrelname | pg_toast_2604_index
idx_scan | 0
idx_tup_read | 0
idx_tup_fetch | 0
-[ RECORD 2 ]-+-------------------------------------
relid | 2832
indexrelid | 2833
schemaname | pg_toast
relname | pg_toast_2606
indexrelname | pg_toast_2606_index
idx_scan | 0
idx_tup_read | 0
idx_tup_fetch | 0
-[ RECORD 3 ]-+-------------------------------------
relid | 2834
indexrelid | 2835
schemaname | pg_toast
relname | pg_toast_2609
indexrelname | pg_toast_2609_index
idx_scan | 0
idx_tup_read | 0
idx_tup_fetch | 0
Unused indexes
postgres=# select * from pg_stat_all_indexes where idx_scan = 0;
-[ RECORD 1 ]-+-------------------------------------
relid | 2830
indexrelid | 2831
schemaname | pg_toast
relname | pg_toast_2604
indexrelname | pg_toast_2604_index
idx_scan | 0
idx_tup_read | 0
idx_tup_fetch | 0
-[ RECORD 2 ]-+-------------------------------------
relid | 2832
indexrelid | 2833
schemaname | pg_toast
relname | pg_toast_2606
indexrelname | pg_toast_2606_index
idx_scan | 0
idx_tup_read | 0
idx_tup_fetch | 0
-[ RECORD 3 ]-+-------------------------------------
relid | 2834
indexrelid | 2835
schemaname | pg_toast
relname | pg_toast_2609
indexrelname | pg_toast_2609_index
idx_scan | 0
idx_tup_read | 0
idx_tup_fetch | 0
Unused indexes are bad.
Uses storage.
Slow down UPDATE, DELETE, INSERT operations.
Extra work for VACUUM.
pg_stat_activity
postgres=# select * from pg_stat_activity;
-[ RECORD 1 ]----+--------------------------------
datid | 13157
datname | postgres
pid | 5111
usesysid | 10
usename | postgres
application_name | psql
client_addr |
client_hostname |
client_port | -1
backend_start | 2016-05-04 19:18:04.728819-07
xact_start | 2016-05-04 20:27:30.39449-07
query_start | 2016-05-04 20:27:30.39449-07
state_change | 2016-05-04 20:27:30.394495-07
waiting | f
state | active
backend_xid |
backend_xmin | 1627
query | select * from pg_stat_activity;
Summary activity
Used connections ratio
postgres=# select
count(*)*100/(select current_setting('max_connections')::int) as connections_ratio
from pg_stat_activity;
-[ RECORD 1 ]-----+--
connections_ratio | 0
postgres=# select
client_addr, usename, datname, count(*)
from pg_stat_activity group by 1,2,3 order by 4 desc;
client_addr | usename | datname | count
-------------+----------+----------+-------
| postgres | postgres | 2
(1 row)
Long queries and xacts
postgres=# select backend_start,xact_start,query_start,state_change from pg_stat_activity;
-[ RECORD 1 ]-+------------------------------
backend_start | 2016-05-04 19:18:04.728819-07
xact_start | 2016-05-04 20:35:04.571186-07
query_start | 2016-05-04 20:35:04.571186-07
state_change | 2016-05-04 20:35:04.571192-07
-[ RECORD 2 ]-+------------------------------
backend_start | 2016-05-04 20:28:45.068657-07
xact_start |
query_start | 2016-05-04 20:28:51.161971-07
state_change | 2016-05-04 20:28:51.187181-07
postgres=# select
postgres-# client_addr, usename, datname,
postgres-# clock_timestamp() - xact_start as xact_age,
postgres-# clock_timestamp() - query_start as query_age,
postgres-# query
postgres-# from pg_stat_activity order by xact_start, query_start;
-[ RECORD 1 ]--------------------------------------------------------
client_addr |
usename | postgres
datname | postgres
xact_age | 00:00:00.001886
query_age | 00:00:00.045951
query | select +
| client_addr, usename, datname, +
| clock_timestamp() - xact_start as xact_age, +
| clock_timestamp() - query_start as query_age, +
| query +
| from pg_stat_activity order by xact_start, query_start;
-[ RECORD 2 ]--------------------------------------------------------
client_addr |
usename | postgres
datname | postgres
xact_age |
query_age | 00:06:54.326014
query | select * from test ;
clock_timestamp() for calculating query or transaction age.
Long queries: remember, terminate, optimize.
Bad xacts
idle in transaction, idle in transaction (aborted) = bad
Warning value: > 5
clock_timestamp() for calculate xact age.
Bad xacts: remember, terminate, optimize app.
postgres=# select * from pg_stat_activity where state in
postgres-# ('idle in transaction', 'idle in transaction (aborted)');
datid | datname | pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | xact_st
art | query_start | state_change | waiting | state | backend_xid | backend_xmin | query
-------+---------+-----+----------+---------+------------------+-------------+-----------------+-------------+---------------+--------
----+-------------+--------------+---------+-------+-------------+--------------+-------
(0 rows)
Waiting clients
waiting = true = bad.
clock_timestamp() for calculating query or xact age.
Enable log_lock_waits GUC, examine server logs.
Use pg_locks for searching blocking query or xact.
Waiting queries: remember, terminate, optimize app.
postgres=# select * from pg_stat_activity where waiting;
(0 rows)
Blocked queries
https://github.com/lesovsky/uber-scripts/blob/master/postgresql/sql/c4_06_show
_locked_queries.sql
http://big-elephants.com/2013-09/exploring-query-locks-in-postgres/
pg_stat_statements
postgres=# SELECT query, calls, total_time, rows, 100.0 * shared_blks_hit /nullif(shared_blks_hit + shared_blks_read, 0) AS hit_percent FROM pg_stat_statements ORDER BY total_time DESC LIMIT 5;
-[ RECORD 1 ]-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
query | create extension pg_stat_statements ;
calls | 1
total_time | 1081.141
rows | 0
hit_percent | 86.4864864864864865
-[ RECORD 2 ]-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
query | /* contrib/pg_stat_statements/pg_stat_statements--1.3.sql */ +
| +
| -- complain if script is sourced in psql, rather than via CREATE EXTENSION +
| +
| +
| -- Register functions. +
| CREATE FUNCTION pg_stat_statements_reset() +
| RETURNS void +
| AS '$libdir/pg_stat_statements' +
| LANGUAGE C; +
| +
| CREATE FUNCTION pg_stat_statements(IN showtext boolean, +
| OUT userid oid, +
| OUT dbid oid, +
| OUT queryid bigint, +
| OUT query text, +
| OUT calls int8, +
| OUT total_time float8, +
| OUT min_time float8, +
| OUT max_time float8, +
| OUT mean_time float8, +
| OUT stddev_time float8, +
| OUT rows int8, +
| OUT shared_blks_hit int8, +
| OUT shared_blks_read int8, +
| OUT shared_blks_dirtied int8, +
| OUT shared_blks_written int8, +
| OUT local_blks_hit int8, +
| OUT local_blks_read int8, +
| OUT local_blks_dirtied int8, +
| OUT local_blks_written int8, +
| OUT temp_blks_read int8, +
| OUT temp_blks_written int8, +
| OUT blk_read_time float8, +
| OUT blk_write_time float8 +
| ) +
| RETURNS SETOF record +
| AS '$libdir/pg_stat_statements', 'pg_stat_statements_1_3' +
| LANGUAGE C STRICT VOLATILE; +
| +
| -- Register a view on the function for ease of use. +
| CREATE VIEW pg_stat_statements AS +
| SELECT * FROM pg_stat_statements(true); +
| +
| GRANT SELECT ON pg_stat_statements TO PUBLIC; +
| +
| -- Don't want this to be available to non-superusers. +
| REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC; +
|
calls | 5
total_time | 880.587
rows | 0
hit_percent | 89.3992932862190813
-[ RECORD 3 ]-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
query | SELECT pg_catalog.quote_ident(name) FROM pg_catalog.pg_available_extensions WHERE substring(pg_catalog.quote_ident(name),?,?)=? AND installed_version IS NULL +
| LIMIT ?
calls | 1
total_time | 196.745
rows | 1
hit_percent | 0.00000000000000000000
-[ RECORD 4 ]-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
query | select * from pg_stat_statements +
| where blk_read_time <> ? order by blk_read_time desc;
calls | 2
total_time | 3.211
rows | 0
hit_percent | 100.0000000000000000
-[ RECORD 5 ]-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
query | SELECT query, calls, total_time, rows, ? * shared_blks_hit /nullif(shared_blks_hit + shared_blks_read, ?) AS hit_percent FROM pg_stat_statements ORDER BY total_time DESC LIMIT ?;
calls | 1
total_time | 0.342
rows | 4
hit_percent |
Statements average time in ms
postgres=# select (sum(total_time) / sum(calls))::numeric(6,3)
postgres-# from pg_stat_statements;
-[ RECORD 1 ]----
numeric | 196.562
The most writing (to shared_buffers) queries
postgres=# select query, shared_blks_dirtied
postgres-# from pg_stat_statements
postgres-# where shared_blks_dirtied > 0 order by 2 desc;
-[ RECORD 1 ]-------+---------------------------------------------------------------------------
query | create extension pg_stat_statements ;
shared_blks_dirtied | 41
-[ RECORD 2 ]-------+---------------------------------------------------------------------------
query | /* contrib/pg_stat_statements/pg_stat_statements--1.3.sql */ +
| +
| -- complain if script is sourced in psql, rather than via CREATE EXTENSION+
| +
| +
| -- Register functions. +
| CREATE FUNCTION pg_stat_statements_reset() +
| RETURNS void +
| AS '$libdir/pg_stat_statements' +
| LANGUAGE C; +
| +
| CREATE FUNCTION pg_stat_statements(IN showtext boolean, +
| OUT userid oid, +
| OUT dbid oid, +
| OUT queryid bigint, +
| OUT query text, +
| OUT calls int8, +
| OUT total_time float8, +
| OUT min_time float8, +
| OUT max_time float8, +
| OUT mean_time float8, +
| OUT stddev_time float8, +
| OUT rows int8, +
| OUT shared_blks_hit int8, +
| OUT shared_blks_read int8, +
| OUT shared_blks_dirtied int8, +
| OUT shared_blks_written int8, +
| OUT local_blks_hit int8, +
| OUT local_blks_read int8, +
| OUT local_blks_dirtied int8, +
| OUT local_blks_written int8, +
| OUT temp_blks_read int8, +
| OUT temp_blks_written int8, +
| OUT blk_read_time float8, +
| OUT blk_write_time float8 +
| ) +
| RETURNS SETOF record +
| AS '$libdir/pg_stat_statements', 'pg_stat_statements_1_3' +
| LANGUAGE C STRICT VOLATILE; +
| +
| -- Register a view on the function for ease of use. +
| CREATE VIEW pg_stat_statements AS +
| SELECT * FROM pg_stat_statements(true); +
| +
| GRANT SELECT ON pg_stat_statements TO PUBLIC; +
| +
| -- Don't want this to be available to non-superusers. +
| REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC; +
|
shared_blks_dirtied | 31
Replication status
Master
postgres=# select pg_is_in_recovery();
-[ RECORD 1 ]-----+--
pg_is_in_recovery | f
postgres=# select pg_current_xlog_insert_location(),pg_current_xlog_location();
-[ RECORD 1 ]-------------------+-----------
pg_current_xlog_insert_location | 0/1202E470
pg_current_xlog_location | 0/1202E470
postgres=# select * from pg_stat_replication ;
-[ RECORD 1 ]----+------------------------------
pid | 7529
usesysid | 10
usename | postgres
application_name | walreceiver
client_addr | 192.168.230.129
client_hostname |
client_port | 41423
backend_start | 2016-05-04 20:45:26.468275-07
backend_xmin |
state | streaming
sent_location | 0/120305F4
write_location | 0/120305F4
flush_location | 0/120305F4
replay_location | 0/120305F4
sync_priority | 0
sync_state | async
Standby
postgres=# select pg_last_xlog_replay_location(),pg_last_xlog_receive_location();
-[ RECORD 1 ]-----------------+-----------
pg_last_xlog_replay_location | 0/1202E540
pg_last_xlog_receive_location | 0/1202E540
postgres=# select pg_is_in_recovery();
-[ RECORD 1 ]-----+--
pg_is_in_recovery | t
Detect the most bloated tables (no need of extensions):
SELECT relname, seq_scan, idx_scan, n_live_tup, n_dead_tup, to_char(n_dead_tup/n_live_tup::real, '999D99')::real AS ratio, pg_size_pretty(pg_relation_size(relid)) FROM pg_stat_all_tables WHERE pg_relation_size(relid) > 1024 * 1024 AND n_live_tup > 0 ORDER BY n_dead_tup/n_live_tup::real DESC LIMIT 10;
List the unused indexes:
SELECT schemaname || '.' || relname AS table, indexrelname AS index, pg_size_pretty(pg_relation_size(i.indexrelid)) AS index_size, idx_scan as index_scans FROM pg_stat_user_indexes ui JOIN pg_index i ON ui.indexrelid = i.indexrelid WHERE NOT indisunique AND idx_scan < 50 AND pg_relation_size(relid) > 1024 * 1024 ORDER BY pg_relation_size(i.indexrelid) / nullif(idx_scan, 0) DESC NULLS FIRST, pg_relation_size(i.indexrelid) DESC;