Alexey Lesovsky, profile picture
Uploaded byAlexey Lesovsky
PDF, PPTX3,819 views

Deep dive into PostgreSQL statistics.

The document is a detailed exploration of PostgreSQL statistics covered in a presentation by Alexey Lesovsky at pgConf US 2016. It discusses the significance of PostgreSQL statistics for monitoring and performance tuning, the types of statistics available, and various methods to effectively utilize them, including queries and tools. The presentation emphasizes the importance of understanding these statistics to resolve issues and optimize database operations.

Education◦
In this document
Powered by AI

Overview of PostgreSQL statistics, presentation by Alexey Lesovsky at PGConf US 2016.

Defines PostgreSQL activity statistics, their effective use, and problem-solving goals.

Details process information in PostgreSQL, focusing on key processes and where time is spent.

Describes the overwhelming amount of information with statistics, lack of history, and absence of native tools.

Lists various built-in views, functions, and extensions available for gathering statistics.

Further discusses statistics sources and their implications on database performance.

Calculates the cache hit ratio from PostgreSQL statistics, aiming for a ratio of over 90%.

Examines database activity metrics, identifying potential anomalies in transaction statistics.

Statistics related to checkpoint activities and the role of background writers in PostgreSQL.

Details about PostgreSQL replication, including current states, locations, and lag analyzes.

Looks into statistics related to table activity, including sequential scans and autovacuum behavior.Explains how autovacuum settings impact dead tuples and maintenance thresholds.

Identifies the negatives of unused indexes on storage, performance, and additional workload.

Summarizes queries and transaction states, focusing on long-running queries and waiting clients.

Analyzes queries using pg_stat_statements, assessing performance, usage, and averages.

Discusses additional tools that enhance PostgreSQL statistics tracking and data performance.

Highlights the usefulness of PostgreSQL statistics and provides links for further reading.

Embed presentation

Download as PDF, PPTX
Deep dive into PostgreSQL statistics. PGConf US 2016, New York Alexey Lesovsky lesovsky@pgco.me
What is PostgreSQL activity statistics. How to use statistics effectively. How to solve problems with statistics. http://goo.gl/uDuSvs Agenda
Nothing about query planner statistics. No tools overview. Don't talk about
Statistics are useful. Statistics are not scary. Where to use statistics. Goals
$ ps hf -u postgres -o cmd /usr/pgsql-9.5/bin/postgres -D /var/lib/pgsql/9.5/data _ postgres: logger process _ postgres: checkpointer process _ postgres: writer process _ postgres: wal writer process _ postgres: autovacuum launcher process _ postgres: stats collector process _ postgres: postgres pgbench [local] idle in transaction _ postgres: postgres pgbench [local] idle _ postgres: postgres pgbench [local] UPDATE _ postgres: postgres pgbench [local] UPDATE waiting _ postgres: postgres pgbench [local] UPDATE Black box
Write Ahead Log Shared Buffers Buffers IO Autovacuum Workers Autovacuum Launcher Background Workers Indexes IO Query Execution Query Planning Client Backends Postmaster Relations IO Logger Process Stats Collector Logical Replication WAL Sender Process Archiver Process Background Writer Checkpointer Process Network Storage Recovery Process WAL Receiver Process Tables/Indexes Data Files Where PostgreSQL spends its time
Too much information (more than 100 counters in 9.5). Statistics are provided as an online counters. No history (but reset functions are available). No native handy stat tools in PostgreSQL. A lot of 3rd party tools and programs. Problems
Too much information (more than 100 counters in 9.5). Statistics are provided as an online counters. No history (but reset functions are available). No native handy stat tools in PostgreSQL. A lot of 3rd party tools and programs. Important to use stats directly from PostgreSQL. Basic SQL skills are required. Problems
Counters in shared memory. Functions. Builtin views. Official extensions in contribs package. Unofficial extensions. Statistics sources
Statistics sources pg_stat_all_tables pg_current_xlog_location() pg_replication_slots pg_stat_replication pg_stat_archiver pg_stat_database_conflicts pg_buffercache pg_stat_database pg_stat_user_tables pg_stat_database pg_stat_bgwriter pgstattuple pg_table_size() pg_database_size pg_index_size() pg_stat_activity EXPLAIN pg_locks pg_stat_user_functions pg_stat_user_indexes pg_statio_all_indexes pg_xlog_location_diff() pg_stat_kcache pg_stat_statements pg_roles pg_database pg_class pg_relation_size() pg_total_relation_size() current_setting() pg_current_xlog_insert_location() pg_last_xact_replay_timestamp() pg_last_xlog_replay_location() pg_tablespace_size() pg_ls_dir() pg_statio_all_sequences pg_statio_sys_tables
Write Ahead Log Shared Buffers Buffers IO Autovacuum Workers Autovacuum Launcher Background Workers Indexes IO Query Execution Query Planning Client Backends Postmaster Tables IO Logger Process Stats Collector Logical Replication WAL Sender Process Archiver Process Background Writer Checkpointer Process Network Storage Recovery Process WAL Receiver Process Tables/Indexes Data Files pg_stat_all_tables pg_current_xlog_location pg_replication_slots pg_stat_replication pg_stat_archiver pg_stat_database_conflicts pg_buffercache pg_stat_database pg_stat_activity pg_stat_user_tables pg_stat_database pg_stat_bgwrier pgstattuplepg_table_size pg_database_size pg_index_size pg_stat_activity EXPLAIN pg_stat_statements pg_locks pg_stat_user_functions pg_stat_all_indexes pg_stat_database pg_statio_all_tables pg_xlog_location_diff nicstat* iostat* pg_stat_kcache pg_stat_statements * - system utils
$ select * from pg_stat_database where datname = 'shop'; -[ RECORD 1 ]--+------------------------------------------- datid | 16414 datname | shop numbackends | 34 xact_commit | 51167155051 xact_rollback | 44781878826 blks_read | 7978770895 blks_hit | 9683551077519 tup_returned | 12507331807583 tup_fetched | 3885840966616 tup_inserted | 2898024857 tup_updated | 3082071349 tup_deleted | 2751363323 conflicts | 0 temp_files | 377675 temp_bytes | 4783712399875 deadlocks | 151 blk_read_time | 214344118.089 blk_write_time | 1260880.747 stats_reset | 2015-05-31 11:37:52.017967+03 pg_stat_database
$ select * from pg_stat_database; ... blks_read | 7978770895 blks_hit | 9683551077519 ... $ select sum(blks_hit)*100/sum(blks_hit+blks_read) as hit_ratio from pg_stat_database; More is better, and not less than 90% Cache hit ratio
$ select * from pg_stat_database; ... xact_commit | 51167155051 xact_rollback | 44781878826 conflicts | 0 temp_files | 377675 temp_bytes | 4783712399875 deadlocks | 151 ... $ select datname, (xact_commit*100)/(xact_commit+xact_rollback) as c_ratio, deadlocks, conflicts, temp_file, pg_size_pretty(temp_bytes) as temp_size from pg_stat_database; Anomalies
$ select * from pg_stat_database; ... xact_commit | 51167155051 < 95 % xact_rollback | 44781878826 > 5 % conflicts | 0 > 10 temp_files | 377675 > 100 temp_bytes | 4783712399875 > 10 GB deadlocks | 151 > 10 ... $ select datname, (xact_commit*100)/(xact_commit+xact_rollback) as c_ratio, deadlocks, conflicts, temp_file, pg_size_pretty(temp_bytes) as temp_size from pg_stat_database; Anomalies
$ select * from pg_stat_database; ... xact_commit | 51167155051 < 95 % xact_rollback | 44781878826 > 5 % conflicts | 0 > 10 temp_files | 377675 > 100 temp_bytes | 4783712399875 > 10 GB deadlocks | 151 > 10 ... Conflicts: pg_stat_database_conflicts, server logs. Deadlocks: server logs + log_lock_waits. Temp files: server logs + log_temp_files, pg_stat_statements. Anomalies
$ select * from pg_stat_bgwriter; -[ RECORD 1 ]---------+------------------------------------ checkpoints_timed | 3267 checkpoints_req | 6 checkpoint_write_time | 10416478591 checkpoint_sync_time | 405039 buffers_checkpoint | 2518065526 buffers_clean | 99602799 maxwritten_clean | 157 buffers_backend | 219356924 buffers_backend_fsync | 0 buffers_alloc | 3477374822 stats_reset | 2015-05-31 11:09:48.413185+03 pg_stat_bgwriter
$ select * from pg_stat_bgwriter; ... checkpoints_timed | 3267 checkpoints_req | 6 ... checkpoints_req > checkpoints_timed = bad postgresql.conf: ● min_wal_size, max_wal_size (checkpoint_segments, >= 9.4) ● checkpoint_timeout ● checkpoint_completion_target Checkpoints
$ select * from pg_stat_bgwriter; ... buffers_clean | 99602799 maxwritten_clean | 157 > 0 buffers_backend_fsync | 0 > 0 ... Clean dirty pages for backends. Helps checkpointer. postgresql.conf: ● bgwriter_delay ● bgwriter_lru_maxpages ● bgwriter_lru_multiplier Background Writer
$ select * from pg_stat_replication; -[ RECORD 1 ]----+------------------------------------ pid | 26921 usesysid | 15588142 usename | replica application_name | walreceiver client_addr | 10.0.0.7 client_hostname | client_port | 32956 backend_start | 2015-10-01 19:14:42.979377+03 backend_xmin | state | streaming sent_location | 1691/EEE65900 write_location | 1691/EEE65900 flush_location | 1691/EEE65900 replay_location | 1691/EEE658D0 sync_priority | 0 sync_state | async pg_stat_replication
$ select * from pg_stat_replication; ... sent_location | 1691/EEE65900 write_location | 1691/EEE65900 flush_location | 1691/EEE65900 replay_location | 1691/EEE658D0 ... 1692/EEE65900 — 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'); Replication lag in bytes $ select client_addr, pg_xlog_location_diff(pg_current_xlog_location(), replay_location) from pg_stat_replication; Replication lag in seconds $ select extract(epoch from now() - pg_last_xact_replay_timestamp()); Replication lag
$ 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; client | pending | network | written | flushed | total -----------+----------+----------+---------+------------+------------ 127.0.0.1 | 0 bytes | 0 bytes | 0 bytes | 48 bytes | 48 bytes 10.1.0.8 | 12 GB | 30 MB | 0 bytes | 156 kB | 12 GB 10.2.0.6 | 0 bytes | 48 bytes | 0 bytes | 551 MB | 552 MB Replication lag
$ select * from pg_stat_all_tables; -[ RECORD 1 ]-------+------------------------------------ relid | 98221 schemaname | public relname | clientsession seq_scan | 192 seq_tup_read | 364544695 idx_scan | 2691939318 idx_tup_fetch | 2669551448 n_tup_ins | 239532851 n_tup_upd | 736119030 n_tup_del | 239898968 n_tup_hot_upd | 497688344 n_live_tup | 3493472 n_dead_tup | 1606 n_mod_since_analyze | 349526 ... pg_stat_all_tables
$ select * from pg_stat_all_tables; ... seq_scan | 192 seq_tup_read | 364544695 > 1000 (seq_tup_avg) ... $ select relname, pg_size_pretty(pg_relation_size(relname::regclass)) as size, seq_scan, seq_tup_read, seq_scan / seq_tup_read as seq_tup_avg from pg_stat_user_tables where seq_tup_read > 0 order by 3,4 desc limit 5; Sequential scans
$ select relname, pg_size_pretty(pg_total_relation_size(relname::regclass)) as full_size, pg_size_pretty(pg_relation_size(relname::regclass)) as table_size, pg_size_pretty(pg_total_relation_size(relname::regclass) - pg_relation_size(relname::regclass)) as index_size from pg_stat_user_tables order by pg_total_relation_size(relname::regclass) desc limit 10; psql meta-commands: dt+ and di+ Tables size
$ select * from pg_stat_all_tables; ... n_tup_upd | 736119030 n_tup_hot_upd | 497688344 ... UPDATE = DELETE + INSERT UPDATE = TABLE UPDATE + INDEX UPDATE Write activity
$ select s.relname, pg_size_pretty(pg_relation_size(relid)), coalesce(n_tup_ins,0) + 2 * coalesce(n_tup_upd,0) - coalesce(n_tup_hot_upd,0) + coalesce(n_tup_del,0) AS total_writes, (coalesce(n_tup_hot_upd,0)::float * 100 / (case when n_tup_upd > 0 then n_tup_upd else 1 end)::float)::numeric(10,2) AS hot_rate, (select v[1] FROM regexp_matches(reloptions::text,E'fillfactor=(d+)') as r(v) limit 1) AS fillfactor from pg_stat_all_tables s join pg_class c ON c.oid=relid order by total_writes desc limit 50; 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? Write activity
| pg_size_pretty | total_writes | hot_rate | fillfactor -+----------------+--------------+----------+------------ | 9418 MB | 391459091 | 5.03 | | 417 MB | 285948760 | 0.00 | | 76 MB | 232031972 | 87.31 | 70 | 7123 MB | 124281107 | 99.36 | 70 Fillfactor determines page packing ratio (between 10 and 100). Tables (and indexes) size overhead. ALTER TABLE table_name SET (fillfactor = 70); Write activity
$ select c.relname, current_setting('autovacuum_vacuum_threshold') as av_base_thresh, current_setting('autovacuum_vacuum_scale_factor') as av_scale_factor, (current_setting('autovacuum_vacuum_threshold')::int + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)) as av_thresh, s.n_dead_tup from pg_stat_user_tables s join pg_class c ON s.relname = c.relname where s.n_dead_tup > (current_setting('autovacuum_vacuum_threshold')::int + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)); | av_base_thresh | av_scale_factor | av_thresh | n_dead_tup +----------------+-----------------+-----------+------------ | 50 | 0.01 | 60302 | 85445 | 50 | 0.01 | 50 | 1349 | 50 | 0.01 | 55 | 12479 | 50 | 0.01 | 103 | 3134 | 50 | 0.01 | 52716 | 173100 Autovacuum queue
$ select c.relname, current_setting('autovacuum_vacuum_threshold') as av_base_thresh, current_setting('autovacuum_vacuum_scale_factor') as av_scale_factor, (current_setting('autovacuum_vacuum_threshold')::int + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)) as av_thresh, s.n_dead_tup from pg_stat_user_tables s join pg_class c ON s.relname = c.relname where s.n_dead_tup > (current_setting('autovacuum_vacuum_threshold')::int + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)); | av_base_thresh | av_scale_factor | av_thresh | n_dead_tup +----------------+-----------------+-----------+------------ | 50 | 0.01 | 60302 | 60545 | 50 | 0.01 | 50 | 1349 | 50 | 0.01 | 55 | 12479 | 50 | 0.01 | 103 | 3134 | 50 | 0.01 | 52716 | 173100 Avito Experience https://github.com/eshkinkot/avito/blob/master/munin/vacuum_queue Autovacuum queue
$ select * from pg_stat_all_indexes where idx_scan = 0; -[ RECORD 1 ]-+------------------------------------------ relid | 98242 indexrelid | 55732253 schemaname | public relname | products indexrelname | products_special2_idx idx_scan | 0 idx_tup_read | 0 idx_tup_fetch | 0 pg_stat_all_indexes
$ select * from pg_stat_all_indexes where idx_scan = 0; ... indexrelname | products_special2_idx idx_scan | 0 0 = bad ... Unused indexes are bad. Uses storage. Slow down UPDATE, DELETE, INSERT operations. Extra work for VACUUM. Unused indexes
$ select * from pg_stat_all_indexes where idx_scan = 0; ... indexrelname | products_special2_idx idx_scan | 0 0 = bad ... Unused indexes are bad. Uses storage. Slow down UPDATE, DELETE, INSERT operations. Extra work for VACUUM. https://goo.gl/0qXDjl http://goo.gl/5QxTm4 Unused indexes
$ select * from pg_stat_activity; -[ RECORD 1 ]----+-------------------------------------------- datid | 16401 datname | ts pid | 116408 usesysid | 16384 usename | tsagent application_name | unicorn_rails worker client_addr | 172.17.0.37 client_hostname | client_port | 50888 backend_start | 2015-10-14 15:18:03.01039+00 xact_start | query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 waiting | f state | idle backend_xid | backend_xmin | query | COMMIT pg_stat_activity
$ select * from pg_stat_activity; ... datname | ts usename | tsagent client_addr | 172.17.0.37 ... Used connections ratio $ select count(*)*100/(select current_setting('max_connections')::int) from pg_stat_activity; Summary activity
$ select * from pg_stat_activity; ... datname | ts usename | tsagent client_addr | 172.17.0.37 ... $ select client_addr, usename, datname, count(*) from pg_stat_activity group by 1,2,3 order by 4 desc; client_addr | usename | datname | count -------------+-----------+---------+------- 127.0.0.1 | cron_role | ts | 508 127.0.0.1 | tsagent | ts | 60 127.0.0.1 | postgres | ts | 1 127.0.0.1 | pupkin | ts | 1 Summary activity
$ select * from pg_stat_activity; ... backend_start | 2015-10-14 15:18:03.01039+00 xact_start | 2015-10-14 15:21:15.336325+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 ... Long queries and xacts
$ select * from pg_stat_activity; ... backend_start | 2015-10-14 15:18:03.01039+00 xact_start | 2015-10-14 15:21:15.336325+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 ... $ 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; Long queries and xacts
$ select * from pg_stat_activity; ... backend_start | 2015-10-14 15:18:03.01039+00 xact_start | 2015-10-14 15:21:15.336325+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 ... $ 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; clock_timestamp() for calculating query or transaction age. Long queries: remember, terminate, optimize. Long queries and xacts
$ select * from pg_stat_activity where state in ('idle in transaction', 'idle in transaction (aborted)'; ... xact_start | 2015-10-14 15:21:21.128192+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 state | idle in transaction ... Bad xacts
$ select * from pg_stat_activity where state in ('idle in transaction', 'idle in transaction (aborted)'; ... xact_start | 2015-10-14 15:21:21.128192+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 state | idle in transaction ... idle in transaction, idle in transaction (aborted) = bad Warning value: > 5 clock_timestamp() for calculate xact age. Bad xacts: remember, terminate, optimize app. Bad xacts
$ select * from pg_stat_activity where waiting; ... xact_start | 2015-10-14 15:21:21.128192+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 waiting | t ... Waiting clients
$ select * from pg_stat_activity where waiting; ... xact_start | 2015-10-14 15:21:21.128192+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 waiting | t ... 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. Waiting clients
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/ locked_item | products waiting | t waiting_query | UPDATE products SET avail = false WHERE id = 154; waiting_mode | RowExclusiveLock waiting_xact_age | 00:00:07.103685 waiting_query_age | 00:00:01.813508 waiting_pid | 5895 waiting_user | app_role waiting_state | active waiting | f locking_query | ALTER TABLE products DROP COLUMN avail; locking_mode | AccessExclusiveLock locking_xact_age | 00:00:16.416441 locking_query_age | 00:00:14.416441 locking_pid | 5844 locking_user | postgres locking_state | idle in transaction Blocked queries
$ select * from pg_stat_statements where blk_read_time <> 0 order by blk_read_time desc; -[ RECORD 1 ]-------+--------------------------------------- userid | 25078444 dbid | 16411 query | SELECT "id" FROM run_plan_xact(?) calls | 11165832 total_time | 11743325.6880088 min_time | 0.581 max_time | 4.298 mean_time | 1.051 stddev_time | 0.142115797855129 rows | 11165832 shared_blks_hit | 351353214 shared_blks_read | 205557 shared_blks_dirtied | 256053 shared_blks_written | 0 local_blks_hit | 0 local_blks_read | 68894 local_blks_dirtied | 68894 local_blks_written | 0 temp_blks_read | 0 temp_blks_written | 0 blk_read_time | 495425.535999976 blk_write_time | 0 pg_stat_statements
$ select * from pg_stat_statements; ... query | SELECT "id" FROM run_plan_xact(?) calls | 11165832 total_time | 11743325.6880088 rows | 11165832 blk_read_time | 495425.535999976 blk_write_time | 0 Statements average time in ms $ select (sum(total_time) / sum(calls))::numeric(6,3) from pg_stat_statements; The most writing (to shared_buffers) queries $ select query, shared_blks_dirtied from pg_stat_statements where shared_blks_dirtied > 0 order by 2 desc; pg_stat_statements
query total time: 15:43:07 (14.9%, CPU: 18.2%, IO: 9.0%) сalls: 476 (0.00%) rows: 476,000 avg_time: 118881.54ms (IO: 21.2%) user: app_user db: ustats query: SELECT filepath, type, deviceuid FROM imvevents WHERE state = ?::eventstate AND servertime BETWEEN $1 AND $2 ORDER BY servertime DESC LIMIT $3 OFFSET $4 https://goo.gl/6025wZ Query reports
query total time: 15:43:07 (14.9%, CPU: 18.2%, IO: 9.0%) сalls: 476 (0.00%) rows: 476,000 avg_time: 118881.54ms (IO: 21.2%) user: app_user db: ustats query: SELECT filepath, type, deviceuid FROM imvevents WHERE state = ?::eventstate AND servertime BETWEEN $1 AND $2 ORDER BY servertime DESC LIMIT $3 OFFSET $4 Use sum() for calculating totals. Calculate queries «contribution» in totals. Resource usage (CPU, IO). Query reports
pg_statio_all_tables, pg_statio_all_indexes. pg_stat_user_functions. Size functions - df *size* pgstattuple (in official contribs package) ● Bloat estimation for tables and indexes. ● Estimation time depends on table (or index) size. pg_buffercache (in official contribs package) ● Shared buffers inspection. ● Heavy performance impact (buffers lock). Behind this talk
pgfincore (3rd party module) ● Low-level operations with tables using mincore(). ● OS page cache inspection. pg_stat_kcache (3rd party module) ● Using getrusage() before and after query. ● CPU usage and real filesystem operations stats. ● Requires pg_stat_statements and postgresql >= 9.4. ● No performance impact. Behind this talk
● The ability to use statistics is useful. ● Statistics are not difficult. ● Statistics help to answer the questions. ● Do experiments. Resume
Author, write more!! www.blog.postgresql-consulting.com The Statistics Collector http://www.postgresql.org/docs/current/static/monitoring-stats.html System Administration Functions http://www.postgresql.org/docs/current/static/functions-admin.html Contrib modules http://www.postgresql.org/docs/current/static/pgstatstatements.html http://www.postgresql.org/docs/current/static/pgstattuple.html http://www.postgresql.org/docs/current/static/pgbuffercache.html https://github.com/klando/pgfincore https://github.com/dalibo/pg_stat_kcache SQL utils and sql code examples https://github.com/PostgreSQL-Consulting/pg-utils Unused indexes http://goo.gl/5QxTm4 https://goo.gl/0qXDjl Query reports https://goo.gl/6025wZ Links
Write Ahead Log Shared Buffers Buffers IO Autovacuum Workers Autovacuum Launcher Background Workers Indexes IO Query Execution Query Planning Client Backends Postmaster Tables IO Logger Process Stats Collector Logical Replication WAL Sender Process Archiver Process Background Writer Checkpointer Process Network Storage Recovery Process WAL Receiver Process Tables/Indexes Data Files pg_stat_all_tables pg_current_xlog_location pg_replication_slots pg_stat_replication pg_stat_archiver pg_stat_database_conflicts pg_buffercache pg_stat_database pg_stat_activity pg_stat_user_tables pg_stat_database pg_stat_bgwrier pgstattuplepg_table_size pg_database_size pg_index_size pg_stat_activity EXPLAIN pg_stat_statements pg_locks pg_stat_user_functions pg_stat_all_indexes pg_stat_database pg_statio_all_tables pg_xlog_location_diff nicstat* iostat* pg_stat_kcache pg_stat_statements Questions

More Related Content

PDF
Deep dive into PostgreSQL statistics.
byAlexey Lesovsky
 
PDF
PostgreSQL Performance Tuning
byelliando dias
 
PDF
MySQL/MariaDB Proxy Software Test
byI Goo Lee
 
PDF
Kevin Kempter PostgreSQL Backup and Recovery Methods @ Postgres Open
byPostgresOpen
 
PPTX
Postgresql Database Administration Basic - Day1
byPoguttuezhiniVP
 
PDF
PostgreSQL and RAM usage
byAlexey Bashtanov
 
PDF
Mastering PostgreSQL Administration
byEDB
 
ODP
PostgreSQL Administration for System Administrators
byCommand Prompt., Inc
 
Deep dive into PostgreSQL statistics.
byAlexey Lesovsky
 
PostgreSQL Performance Tuning
byelliando dias
 
MySQL/MariaDB Proxy Software Test
byI Goo Lee
 
Kevin Kempter PostgreSQL Backup and Recovery Methods @ Postgres Open
byPostgresOpen
 
Postgresql Database Administration Basic - Day1
byPoguttuezhiniVP
 
PostgreSQL and RAM usage
byAlexey Bashtanov
 
Mastering PostgreSQL Administration
byEDB
 
PostgreSQL Administration for System Administrators
byCommand Prompt., Inc
 

What's hot

PDF
How does PostgreSQL work with disks: a DBA's checklist in detail. PGConf.US 2015
byPostgreSQL-Consulting
 
PDF
Introduction VAUUM, Freezing, XID wraparound
byMasahiko Sawada
 
PDF
[pgday.Seoul 2022] PostgreSQL구조 - 윤성재
byPgDay.Seoul
 
PDF
CephFS Update
byCeph Community
 
PDF
PostgreSQL Deep Internal
byEXEM
 
DOCX
Keepalived+MaxScale+MariaDB_운영매뉴얼_1.0.docx
byNeoClova
 
PDF
PostgreSQL Extensions: A deeper look
byJignesh Shah
 
PDF
PostgreSQL na EXT4, XFS, BTRFS a ZFS / FOSDEM PgDay 2016
byTomas Vondra
 
PDF
ClickHouse materialized views - a secret weapon for high performance analytic...
byAltinity Ltd
 
PPTX
Getting started with postgresql
bybotsplash.com
 
PDF
The InnoDB Storage Engine for MySQL
byMorgan Tocker
 
PDF
InnoDB Internal
bymysqlops
 
PDF
MySQL Performance Schema in Action: the Complete Tutorial
bySveta Smirnova
 
PDF
PostgreSQL WAL for DBAs
byPGConf APAC
 
PDF
Get to know PostgreSQL!
byOddbjørn Steffensen
 
PDF
Advanced Postgres Monitoring
byDenish Patel
 
PDF
Introduction to Vacuum Freezing and XID
byPGConf APAC
 
PDF
Streaming replication in practice
byAlexey Lesovsky
 
PDF
MySQL topology healing at OLA.
byMydbops
 
PDF
Paris Redis Meetup Introduction
byGregory Boissinot
 
How does PostgreSQL work with disks: a DBA's checklist in detail. PGConf.US 2015
byPostgreSQL-Consulting
 
Introduction VAUUM, Freezing, XID wraparound
byMasahiko Sawada
 
[pgday.Seoul 2022] PostgreSQL구조 - 윤성재
byPgDay.Seoul
 
CephFS Update
byCeph Community
 
PostgreSQL Deep Internal
byEXEM
 
Keepalived+MaxScale+MariaDB_운영매뉴얼_1.0.docx
byNeoClova
 
PostgreSQL Extensions: A deeper look
byJignesh Shah
 
PostgreSQL na EXT4, XFS, BTRFS a ZFS / FOSDEM PgDay 2016
byTomas Vondra
 
ClickHouse materialized views - a secret weapon for high performance analytic...
byAltinity Ltd
 
Getting started with postgresql
bybotsplash.com
 
The InnoDB Storage Engine for MySQL
byMorgan Tocker
 
InnoDB Internal
bymysqlops
 
MySQL Performance Schema in Action: the Complete Tutorial
bySveta Smirnova
 
PostgreSQL WAL for DBAs
byPGConf APAC
 
Get to know PostgreSQL!
byOddbjørn Steffensen
 
Advanced Postgres Monitoring
byDenish Patel
 
Introduction to Vacuum Freezing and XID
byPGConf APAC
 
Streaming replication in practice
byAlexey Lesovsky
 
MySQL topology healing at OLA.
byMydbops
 
Paris Redis Meetup Introduction
byGregory Boissinot
 

Viewers also liked

PDF
PostgreSQL Vacuum: Nine Circles of Hell
byAlexey Lesovsky
 
PDF
Pgcenter overview
byAlexey Lesovsky
 
PDF
Understanding PostgreSQL LW Locks
byJignesh Shah
 
PDF
Streaming replication in practice
byAlexey Lesovsky
 
PDF
Nine Circles of Inferno or Explaining the PostgreSQL Vacuum
byAlexey Lesovsky
 
PDF
Troubleshooting PostgreSQL Streaming Replication
byAlexey Lesovsky
 
PDF
PostgreSQL worst practices, version FOSDEM PGDay 2017 by Ilya Kosmodemiansky
byPostgreSQL-Consulting
 
PostgreSQL Vacuum: Nine Circles of Hell
byAlexey Lesovsky
 
Pgcenter overview
byAlexey Lesovsky
 
Understanding PostgreSQL LW Locks
byJignesh Shah
 
Streaming replication in practice
byAlexey Lesovsky
 
Nine Circles of Inferno or Explaining the PostgreSQL Vacuum
byAlexey Lesovsky
 
Troubleshooting PostgreSQL Streaming Replication
byAlexey Lesovsky
 
PostgreSQL worst practices, version FOSDEM PGDay 2017 by Ilya Kosmodemiansky
byPostgreSQL-Consulting
 

Similar to Deep dive into PostgreSQL statistics.

PDF
Monitoring Postgres at Scale | PGConf.ASIA 2018 | Lukas Fittl
byCitus Data
 
PDF
Monitoring Postgres at Scale | PostgresConf US 2018 | Lukas Fittl
byCitus Data
 
PDF
Deep dive into PostgreSQL statistics.
byAlexey Lesovsky
 
PDF
Deep dive into PostgreSQL internal statistics / Алексей Лесовский (PostgreSQL...
byOntico
 
PDF
Webinar slides: An Introduction to Performance Monitoring for PostgreSQL
bySeveralnines
 
PDF
PGConf APAC 2018 - Monitoring PostgreSQL at Scale
byPGConf APAC
 
PDF
Troubleshooting PostgreSQL with pgCenter
byAlexey Lesovsky
 
PPTX
Postgresql Database Administration- Day4
byPoguttuezhiniVP
 
PDF
Introduction to PostgreSQL for System Administrators
byJignesh Shah
 
PDF
Aplicações 10x a 100x mais rápida com o postgre sql
byFabio Telles Rodriguez
 
PDF
PostgreSQL on Solaris
byTheo Schlossnagle
 
PDF
PostgreSQL on Solaris
byTheo Schlossnagle
 
PDF
pg_proctab: Accessing System Stats in PostgreSQL
byMark Wong
 
PDF
pg_proctab: Accessing System Stats in PostgreSQL
byCommand Prompt., Inc
 
PDF
Optimizing your app by understanding your Postgres | RailsConf 2019 | Samay S...
byCitus Data
 
PDF
pg_proctab: Accessing System Stats in PostgreSQL
byMark Wong
 
PDF
pg_proctab: Accessing System Stats in PostgreSQL
byCommand Prompt., Inc
 
PDF
pg_proctab: Accessing System Stats in PostgreSQL
byMark Wong
 
PDF
Explain this!
byFabio Telles Rodriguez
 
PDF
The Essential postgresql.conf
byRobert Treat
 
Monitoring Postgres at Scale | PGConf.ASIA 2018 | Lukas Fittl
byCitus Data
 
Monitoring Postgres at Scale | PostgresConf US 2018 | Lukas Fittl
byCitus Data
 
Deep dive into PostgreSQL statistics.
byAlexey Lesovsky
 
Deep dive into PostgreSQL internal statistics / Алексей Лесовский (PostgreSQL...
byOntico
 
Webinar slides: An Introduction to Performance Monitoring for PostgreSQL
bySeveralnines
 
PGConf APAC 2018 - Monitoring PostgreSQL at Scale
byPGConf APAC
 
Troubleshooting PostgreSQL with pgCenter
byAlexey Lesovsky
 
Postgresql Database Administration- Day4
byPoguttuezhiniVP
 
Introduction to PostgreSQL for System Administrators
byJignesh Shah
 
Aplicações 10x a 100x mais rápida com o postgre sql
byFabio Telles Rodriguez
 
PostgreSQL on Solaris
byTheo Schlossnagle
 
PostgreSQL on Solaris
byTheo Schlossnagle
 
pg_proctab: Accessing System Stats in PostgreSQL
byMark Wong
 
pg_proctab: Accessing System Stats in PostgreSQL
byCommand Prompt., Inc
 
Optimizing your app by understanding your Postgres | RailsConf 2019 | Samay S...
byCitus Data
 
pg_proctab: Accessing System Stats in PostgreSQL
byMark Wong
 
pg_proctab: Accessing System Stats in PostgreSQL
byCommand Prompt., Inc
 
pg_proctab: Accessing System Stats in PostgreSQL
byMark Wong
 
Explain this!
byFabio Telles Rodriguez
 
The Essential postgresql.conf
byRobert Treat
 

More from Alexey Lesovsky

PDF
Отладка и устранение проблем в PostgreSQL Streaming Replication.
byAlexey Lesovsky
 
PDF
Call of Postgres: Advanced Operations (part 5)
byAlexey Lesovsky
 
PDF
Call of Postgres: Advanced Operations (part 4)
byAlexey Lesovsky
 
PDF
Call of Postgres: Advanced Operations (part 3)
byAlexey Lesovsky
 
PDF
Call of Postgres: Advanced Operations (part 2)
byAlexey Lesovsky
 
PDF
Call of Postgres: Advanced Operations (part 1)
byAlexey Lesovsky
 
PDF
PostgreSQL Streaming Replication
byAlexey Lesovsky
 
PDF
GitLab PostgresMortem: Lessons Learned
byAlexey Lesovsky
 
PDF
Tuning Linux for Databases.
byAlexey Lesovsky
 
PDF
Managing PostgreSQL with PgCenter
byAlexey Lesovsky
 
PDF
PostgreSQL Streaming Replication Cheatsheet
byAlexey Lesovsky
 
PDF
Highload 2014. PostgreSQL: ups, DevOps.
byAlexey Lesovsky
 
PDF
PostgreSQL Troubleshoot On-line, (RITfest 2015 meetup at Moscow, Russia).
byAlexey Lesovsky
 
PDF
Linux tuning for PostgreSQL at Secon 2015
byAlexey Lesovsky
 
Отладка и устранение проблем в PostgreSQL Streaming Replication.
byAlexey Lesovsky
 
Call of Postgres: Advanced Operations (part 5)
byAlexey Lesovsky
 
Call of Postgres: Advanced Operations (part 4)
byAlexey Lesovsky
 
Call of Postgres: Advanced Operations (part 3)
byAlexey Lesovsky
 
Call of Postgres: Advanced Operations (part 2)
byAlexey Lesovsky
 
Call of Postgres: Advanced Operations (part 1)
byAlexey Lesovsky
 
PostgreSQL Streaming Replication
byAlexey Lesovsky
 
GitLab PostgresMortem: Lessons Learned
byAlexey Lesovsky
 
Tuning Linux for Databases.
byAlexey Lesovsky
 
Managing PostgreSQL with PgCenter
byAlexey Lesovsky
 
PostgreSQL Streaming Replication Cheatsheet
byAlexey Lesovsky
 
Highload 2014. PostgreSQL: ups, DevOps.
byAlexey Lesovsky
 
PostgreSQL Troubleshoot On-line, (RITfest 2015 meetup at Moscow, Russia).
byAlexey Lesovsky
 
Linux tuning for PostgreSQL at Secon 2015
byAlexey Lesovsky
 

Recently uploaded

PDF
Blood Group Incompatibility: Rh Factor and Erythroblastosis Fetalis
bySudhandraKarthi
 
PDF
IMANI Africa files RTI request seeking full disclosure on 2026 SIM registrati...
bynservice241
 
PPTX
How to Configure Push & Pull Rule in Odoo 18 Inventory
byCeline George
 
PDF
Types of eggs and Egg membranes (Developmental Zoology)
bySudhandraKarthi
 
PPTX
Repeat Orders_ Use Odoo Blanket Agreement
byCeline George
 
PPTX
Expected Revenue Report In Odoo 18 CRM
byCeline George
 
PPTX
TAMIS & TEMS - HOW, WHY and THE STEPS IN PROCTOLOGY
byJohn Thanakumar
 
PDF
Scalable-MADDPG-Based Cooperative Target Invasion for a Multi-USV System.pdf
byMan_Ebook
 
PPTX
3 G8_Q3_L3_ (Cartoon as Representation in Opinion Editorial Article).pptx
byNorafeSahagun
 
PDF
International Men's Day Event: Breaking the Silence: Embracing Vulnerability ...
byAssociation for Project Management
 
PPTX
Multiple Linear Regression - Least Square Method X₁ on X₂ and X₃
bySundar B N
 
PPTX
Introduction-to-Anatomy-and-Physiology.pptx
byAshish Umale
 
PDF
Risk management in Moroccan public hospitals_ a literature review
byMan_Ebook
 
PPTX
AN EXTREMELY BORING GENERAL QUIZ FOR UG.pptx
bySriramG47
 
PPTX
How to Manage Package Reservation in Odoo 18 Inventory
byCeline George
 
PPTX
Steve Hale - Developing Elite Young Goalkeepers 2024.pptx
bypjmfd
 
PPTX
Semester 6 Unit 2 Club foot (talipes).pptx
bysachin7989
 
PPTX
4 G8_Q3_L4 (Evaluating opinion editorials for textual evidence and quality).pptx
byNorafeSahagun
 
PDF
Cultivating Greatness Pune's Best Preschools and Schools.pdf
byWellington College
 
PPTX
How to Create Lead_Opportunity From Odoo 18 Website
byCeline George
 
Blood Group Incompatibility: Rh Factor and Erythroblastosis Fetalis
bySudhandraKarthi
 
IMANI Africa files RTI request seeking full disclosure on 2026 SIM registrati...
bynservice241
 
How to Configure Push & Pull Rule in Odoo 18 Inventory
byCeline George
 
Types of eggs and Egg membranes (Developmental Zoology)
bySudhandraKarthi
 
Repeat Orders_ Use Odoo Blanket Agreement
byCeline George
 
Expected Revenue Report In Odoo 18 CRM
byCeline George
 
TAMIS & TEMS - HOW, WHY and THE STEPS IN PROCTOLOGY
byJohn Thanakumar
 
Scalable-MADDPG-Based Cooperative Target Invasion for a Multi-USV System.pdf
byMan_Ebook
 
3 G8_Q3_L3_ (Cartoon as Representation in Opinion Editorial Article).pptx
byNorafeSahagun
 
International Men's Day Event: Breaking the Silence: Embracing Vulnerability ...
byAssociation for Project Management
 
Multiple Linear Regression - Least Square Method X₁ on X₂ and X₃
bySundar B N
 
Introduction-to-Anatomy-and-Physiology.pptx
byAshish Umale
 
Risk management in Moroccan public hospitals_ a literature review
byMan_Ebook
 
AN EXTREMELY BORING GENERAL QUIZ FOR UG.pptx
bySriramG47
 
How to Manage Package Reservation in Odoo 18 Inventory
byCeline George
 
Steve Hale - Developing Elite Young Goalkeepers 2024.pptx
bypjmfd
 
Semester 6 Unit 2 Club foot (talipes).pptx
bysachin7989
 
4 G8_Q3_L4 (Evaluating opinion editorials for textual evidence and quality).pptx
byNorafeSahagun
 
Cultivating Greatness Pune's Best Preschools and Schools.pdf
byWellington College
 
How to Create Lead_Opportunity From Odoo 18 Website
byCeline George
 

Deep dive into PostgreSQL statistics.

  • 1.
    Deep dive intoPostgreSQL statistics. PGConf US 2016, New York Alexey Lesovsky lesovsky@pgco.me
  • 2.
    What is PostgreSQLactivity statistics. How to use statistics effectively. How to solve problems with statistics. http://goo.gl/uDuSvs Agenda
  • 3.
    Nothing about queryplanner statistics. No tools overview. Don't talk about
  • 4.
    Statistics are useful. Statisticsare not scary. Where to use statistics. Goals
  • 5.
    $ ps hf-u postgres -o cmd /usr/pgsql-9.5/bin/postgres -D /var/lib/pgsql/9.5/data _ postgres: logger process _ postgres: checkpointer process _ postgres: writer process _ postgres: wal writer process _ postgres: autovacuum launcher process _ postgres: stats collector process _ postgres: postgres pgbench [local] idle in transaction _ postgres: postgres pgbench [local] idle _ postgres: postgres pgbench [local] UPDATE _ postgres: postgres pgbench [local] UPDATE waiting _ postgres: postgres pgbench [local] UPDATE Black box
  • 6.
    Write Ahead Log Shared Buffers BuffersIO Autovacuum Workers Autovacuum Launcher Background Workers Indexes IO Query Execution Query Planning Client Backends Postmaster Relations IO Logger Process Stats Collector Logical Replication WAL Sender Process Archiver Process Background Writer Checkpointer Process Network Storage Recovery Process WAL Receiver Process Tables/Indexes Data Files Where PostgreSQL spends its time
  • 7.
    Too much information(more than 100 counters in 9.5). Statistics are provided as an online counters. No history (but reset functions are available). No native handy stat tools in PostgreSQL. A lot of 3rd party tools and programs. Problems
  • 8.
    Too much information(more than 100 counters in 9.5). Statistics are provided as an online counters. No history (but reset functions are available). No native handy stat tools in PostgreSQL. A lot of 3rd party tools and programs. Important to use stats directly from PostgreSQL. Basic SQL skills are required. Problems
  • 9.
    Counters in sharedmemory. Functions. Builtin views. Official extensions in contribs package. Unofficial extensions. Statistics sources
  • 10.
  • 11.
    Write Ahead Log Shared Buffers BuffersIO Autovacuum Workers Autovacuum Launcher Background Workers Indexes IO Query Execution Query Planning Client Backends Postmaster Tables IO Logger Process Stats Collector Logical Replication WAL Sender Process Archiver Process Background Writer Checkpointer Process Network Storage Recovery Process WAL Receiver Process Tables/Indexes Data Files pg_stat_all_tables pg_current_xlog_location pg_replication_slots pg_stat_replication pg_stat_archiver pg_stat_database_conflicts pg_buffercache pg_stat_database pg_stat_activity pg_stat_user_tables pg_stat_database pg_stat_bgwrier pgstattuplepg_table_size pg_database_size pg_index_size pg_stat_activity EXPLAIN pg_stat_statements pg_locks pg_stat_user_functions pg_stat_all_indexes pg_stat_database pg_statio_all_tables pg_xlog_location_diff nicstat* iostat* pg_stat_kcache pg_stat_statements * - system utils
  • 12.
    $ select *from pg_stat_database where datname = 'shop'; -[ RECORD 1 ]--+------------------------------------------- datid | 16414 datname | shop numbackends | 34 xact_commit | 51167155051 xact_rollback | 44781878826 blks_read | 7978770895 blks_hit | 9683551077519 tup_returned | 12507331807583 tup_fetched | 3885840966616 tup_inserted | 2898024857 tup_updated | 3082071349 tup_deleted | 2751363323 conflicts | 0 temp_files | 377675 temp_bytes | 4783712399875 deadlocks | 151 blk_read_time | 214344118.089 blk_write_time | 1260880.747 stats_reset | 2015-05-31 11:37:52.017967+03 pg_stat_database
  • 13.
    $ select *from pg_stat_database; ... blks_read | 7978770895 blks_hit | 9683551077519 ... $ select sum(blks_hit)*100/sum(blks_hit+blks_read) as hit_ratio from pg_stat_database; More is better, and not less than 90% Cache hit ratio
  • 14.
    $ select *from pg_stat_database; ... xact_commit | 51167155051 xact_rollback | 44781878826 conflicts | 0 temp_files | 377675 temp_bytes | 4783712399875 deadlocks | 151 ... $ select datname, (xact_commit*100)/(xact_commit+xact_rollback) as c_ratio, deadlocks, conflicts, temp_file, pg_size_pretty(temp_bytes) as temp_size from pg_stat_database; Anomalies
  • 15.
    $ select *from pg_stat_database; ... xact_commit | 51167155051 < 95 % xact_rollback | 44781878826 > 5 % conflicts | 0 > 10 temp_files | 377675 > 100 temp_bytes | 4783712399875 > 10 GB deadlocks | 151 > 10 ... $ select datname, (xact_commit*100)/(xact_commit+xact_rollback) as c_ratio, deadlocks, conflicts, temp_file, pg_size_pretty(temp_bytes) as temp_size from pg_stat_database; Anomalies
  • 16.
    $ select *from pg_stat_database; ... xact_commit | 51167155051 < 95 % xact_rollback | 44781878826 > 5 % conflicts | 0 > 10 temp_files | 377675 > 100 temp_bytes | 4783712399875 > 10 GB deadlocks | 151 > 10 ... Conflicts: pg_stat_database_conflicts, server logs. Deadlocks: server logs + log_lock_waits. Temp files: server logs + log_temp_files, pg_stat_statements. Anomalies
  • 17.
    $ select *from pg_stat_bgwriter; -[ RECORD 1 ]---------+------------------------------------ checkpoints_timed | 3267 checkpoints_req | 6 checkpoint_write_time | 10416478591 checkpoint_sync_time | 405039 buffers_checkpoint | 2518065526 buffers_clean | 99602799 maxwritten_clean | 157 buffers_backend | 219356924 buffers_backend_fsync | 0 buffers_alloc | 3477374822 stats_reset | 2015-05-31 11:09:48.413185+03 pg_stat_bgwriter
  • 18.
    $ select *from pg_stat_bgwriter; ... checkpoints_timed | 3267 checkpoints_req | 6 ... checkpoints_req > checkpoints_timed = bad postgresql.conf: ● min_wal_size, max_wal_size (checkpoint_segments, >= 9.4) ● checkpoint_timeout ● checkpoint_completion_target Checkpoints
  • 19.
    $ select *from pg_stat_bgwriter; ... buffers_clean | 99602799 maxwritten_clean | 157 > 0 buffers_backend_fsync | 0 > 0 ... Clean dirty pages for backends. Helps checkpointer. postgresql.conf: ● bgwriter_delay ● bgwriter_lru_maxpages ● bgwriter_lru_multiplier Background Writer
  • 20.
    $ select *from pg_stat_replication; -[ RECORD 1 ]----+------------------------------------ pid | 26921 usesysid | 15588142 usename | replica application_name | walreceiver client_addr | 10.0.0.7 client_hostname | client_port | 32956 backend_start | 2015-10-01 19:14:42.979377+03 backend_xmin | state | streaming sent_location | 1691/EEE65900 write_location | 1691/EEE65900 flush_location | 1691/EEE65900 replay_location | 1691/EEE658D0 sync_priority | 0 sync_state | async pg_stat_replication
  • 21.
    $ select *from pg_stat_replication; ... sent_location | 1691/EEE65900 write_location | 1691/EEE65900 flush_location | 1691/EEE65900 replay_location | 1691/EEE658D0 ... 1692/EEE65900 — location in transaction log (WAL) All values are equal = ideal Replication lag
  • 22.
    Lag causes: Networking Storage CPU How manybytes written in WAL $ select pg_xlog_location_diff(pg_current_xlog_location(),'0/00000000'); Replication lag in bytes $ select client_addr, pg_xlog_location_diff(pg_current_xlog_location(), replay_location) from pg_stat_replication; Replication lag in seconds $ select extract(epoch from now() - pg_last_xact_replay_timestamp()); Replication lag
  • 23.
    $ select client_addr asclient, 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; client | pending | network | written | flushed | total -----------+----------+----------+---------+------------+------------ 127.0.0.1 | 0 bytes | 0 bytes | 0 bytes | 48 bytes | 48 bytes 10.1.0.8 | 12 GB | 30 MB | 0 bytes | 156 kB | 12 GB 10.2.0.6 | 0 bytes | 48 bytes | 0 bytes | 551 MB | 552 MB Replication lag
  • 24.
    $ select *from pg_stat_all_tables; -[ RECORD 1 ]-------+------------------------------------ relid | 98221 schemaname | public relname | clientsession seq_scan | 192 seq_tup_read | 364544695 idx_scan | 2691939318 idx_tup_fetch | 2669551448 n_tup_ins | 239532851 n_tup_upd | 736119030 n_tup_del | 239898968 n_tup_hot_upd | 497688344 n_live_tup | 3493472 n_dead_tup | 1606 n_mod_since_analyze | 349526 ... pg_stat_all_tables
  • 25.
    $ select *from pg_stat_all_tables; ... seq_scan | 192 seq_tup_read | 364544695 > 1000 (seq_tup_avg) ... $ select relname, pg_size_pretty(pg_relation_size(relname::regclass)) as size, seq_scan, seq_tup_read, seq_scan / seq_tup_read as seq_tup_avg from pg_stat_user_tables where seq_tup_read > 0 order by 3,4 desc limit 5; Sequential scans
  • 26.
    $ select relname, pg_size_pretty(pg_total_relation_size(relname::regclass)) as full_size, pg_size_pretty(pg_relation_size(relname::regclass))as table_size, pg_size_pretty(pg_total_relation_size(relname::regclass) - pg_relation_size(relname::regclass)) as index_size from pg_stat_user_tables order by pg_total_relation_size(relname::regclass) desc limit 10; psql meta-commands: dt+ and di+ Tables size
  • 27.
    $ select *from pg_stat_all_tables; ... n_tup_upd | 736119030 n_tup_hot_upd | 497688344 ... UPDATE = DELETE + INSERT UPDATE = TABLE UPDATE + INDEX UPDATE Write activity
  • 28.
    $ select s.relname, pg_size_pretty(pg_relation_size(relid)), coalesce(n_tup_ins,0) +2 * coalesce(n_tup_upd,0) - coalesce(n_tup_hot_upd,0) + coalesce(n_tup_del,0) AS total_writes, (coalesce(n_tup_hot_upd,0)::float * 100 / (case when n_tup_upd > 0 then n_tup_upd else 1 end)::float)::numeric(10,2) AS hot_rate, (select v[1] FROM regexp_matches(reloptions::text,E'fillfactor=(d+)') as r(v) limit 1) AS fillfactor from pg_stat_all_tables s join pg_class c ON c.oid=relid order by total_writes desc limit 50; 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? Write activity
  • 29.
    | pg_size_pretty |total_writes | hot_rate | fillfactor -+----------------+--------------+----------+------------ | 9418 MB | 391459091 | 5.03 | | 417 MB | 285948760 | 0.00 | | 76 MB | 232031972 | 87.31 | 70 | 7123 MB | 124281107 | 99.36 | 70 Fillfactor determines page packing ratio (between 10 and 100). Tables (and indexes) size overhead. ALTER TABLE table_name SET (fillfactor = 70); Write activity
  • 30.
    $ select c.relname, current_setting('autovacuum_vacuum_threshold')as av_base_thresh, current_setting('autovacuum_vacuum_scale_factor') as av_scale_factor, (current_setting('autovacuum_vacuum_threshold')::int + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)) as av_thresh, s.n_dead_tup from pg_stat_user_tables s join pg_class c ON s.relname = c.relname where s.n_dead_tup > (current_setting('autovacuum_vacuum_threshold')::int + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)); | av_base_thresh | av_scale_factor | av_thresh | n_dead_tup +----------------+-----------------+-----------+------------ | 50 | 0.01 | 60302 | 85445 | 50 | 0.01 | 50 | 1349 | 50 | 0.01 | 55 | 12479 | 50 | 0.01 | 103 | 3134 | 50 | 0.01 | 52716 | 173100 Autovacuum queue
  • 31.
    $ select c.relname, current_setting('autovacuum_vacuum_threshold')as av_base_thresh, current_setting('autovacuum_vacuum_scale_factor') as av_scale_factor, (current_setting('autovacuum_vacuum_threshold')::int + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)) as av_thresh, s.n_dead_tup from pg_stat_user_tables s join pg_class c ON s.relname = c.relname where s.n_dead_tup > (current_setting('autovacuum_vacuum_threshold')::int + (current_setting('autovacuum_vacuum_scale_factor')::float * c.reltuples)); | av_base_thresh | av_scale_factor | av_thresh | n_dead_tup +----------------+-----------------+-----------+------------ | 50 | 0.01 | 60302 | 60545 | 50 | 0.01 | 50 | 1349 | 50 | 0.01 | 55 | 12479 | 50 | 0.01 | 103 | 3134 | 50 | 0.01 | 52716 | 173100 Avito Experience https://github.com/eshkinkot/avito/blob/master/munin/vacuum_queue Autovacuum queue
  • 32.
    $ select *from pg_stat_all_indexes where idx_scan = 0; -[ RECORD 1 ]-+------------------------------------------ relid | 98242 indexrelid | 55732253 schemaname | public relname | products indexrelname | products_special2_idx idx_scan | 0 idx_tup_read | 0 idx_tup_fetch | 0 pg_stat_all_indexes
  • 33.
    $ select *from pg_stat_all_indexes where idx_scan = 0; ... indexrelname | products_special2_idx idx_scan | 0 0 = bad ... Unused indexes are bad. Uses storage. Slow down UPDATE, DELETE, INSERT operations. Extra work for VACUUM. Unused indexes
  • 34.
    $ select *from pg_stat_all_indexes where idx_scan = 0; ... indexrelname | products_special2_idx idx_scan | 0 0 = bad ... Unused indexes are bad. Uses storage. Slow down UPDATE, DELETE, INSERT operations. Extra work for VACUUM. https://goo.gl/0qXDjl http://goo.gl/5QxTm4 Unused indexes
  • 35.
    $ select *from pg_stat_activity; -[ RECORD 1 ]----+-------------------------------------------- datid | 16401 datname | ts pid | 116408 usesysid | 16384 usename | tsagent application_name | unicorn_rails worker client_addr | 172.17.0.37 client_hostname | client_port | 50888 backend_start | 2015-10-14 15:18:03.01039+00 xact_start | query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 waiting | f state | idle backend_xid | backend_xmin | query | COMMIT pg_stat_activity
  • 36.
    $ select *from pg_stat_activity; ... datname | ts usename | tsagent client_addr | 172.17.0.37 ... Used connections ratio $ select count(*)*100/(select current_setting('max_connections')::int) from pg_stat_activity; Summary activity
  • 37.
    $ select *from pg_stat_activity; ... datname | ts usename | tsagent client_addr | 172.17.0.37 ... $ select client_addr, usename, datname, count(*) from pg_stat_activity group by 1,2,3 order by 4 desc; client_addr | usename | datname | count -------------+-----------+---------+------- 127.0.0.1 | cron_role | ts | 508 127.0.0.1 | tsagent | ts | 60 127.0.0.1 | postgres | ts | 1 127.0.0.1 | pupkin | ts | 1 Summary activity
  • 38.
    $ select *from pg_stat_activity; ... backend_start | 2015-10-14 15:18:03.01039+00 xact_start | 2015-10-14 15:21:15.336325+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 ... Long queries and xacts
  • 39.
    $ select *from pg_stat_activity; ... backend_start | 2015-10-14 15:18:03.01039+00 xact_start | 2015-10-14 15:21:15.336325+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 ... $ 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; Long queries and xacts
  • 40.
    $ select *from pg_stat_activity; ... backend_start | 2015-10-14 15:18:03.01039+00 xact_start | 2015-10-14 15:21:15.336325+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 ... $ 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; clock_timestamp() for calculating query or transaction age. Long queries: remember, terminate, optimize. Long queries and xacts
  • 41.
    $ select *from pg_stat_activity where state in ('idle in transaction', 'idle in transaction (aborted)'; ... xact_start | 2015-10-14 15:21:21.128192+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 state | idle in transaction ... Bad xacts
  • 42.
    $ select *from pg_stat_activity where state in ('idle in transaction', 'idle in transaction (aborted)'; ... xact_start | 2015-10-14 15:21:21.128192+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 state | idle in transaction ... idle in transaction, idle in transaction (aborted) = bad Warning value: > 5 clock_timestamp() for calculate xact age. Bad xacts: remember, terminate, optimize app. Bad xacts
  • 43.
    $ select *from pg_stat_activity where waiting; ... xact_start | 2015-10-14 15:21:21.128192+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 waiting | t ... Waiting clients
  • 44.
    $ select *from pg_stat_activity where waiting; ... xact_start | 2015-10-14 15:21:21.128192+00 query_start | 2015-10-14 15:21:30.336325+00 state_change | 2015-10-14 15:21:30.33635+00 waiting | t ... 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. Waiting clients
  • 45.
    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/ locked_item | products waiting| t waiting_query | UPDATE products SET avail = false WHERE id = 154; waiting_mode | RowExclusiveLock waiting_xact_age | 00:00:07.103685 waiting_query_age | 00:00:01.813508 waiting_pid | 5895 waiting_user | app_role waiting_state | active waiting | f locking_query | ALTER TABLE products DROP COLUMN avail; locking_mode | AccessExclusiveLock locking_xact_age | 00:00:16.416441 locking_query_age | 00:00:14.416441 locking_pid | 5844 locking_user | postgres locking_state | idle in transaction Blocked queries
  • 46.
    $ select *from pg_stat_statements where blk_read_time <> 0 order by blk_read_time desc; -[ RECORD 1 ]-------+--------------------------------------- userid | 25078444 dbid | 16411 query | SELECT "id" FROM run_plan_xact(?) calls | 11165832 total_time | 11743325.6880088 min_time | 0.581 max_time | 4.298 mean_time | 1.051 stddev_time | 0.142115797855129 rows | 11165832 shared_blks_hit | 351353214 shared_blks_read | 205557 shared_blks_dirtied | 256053 shared_blks_written | 0 local_blks_hit | 0 local_blks_read | 68894 local_blks_dirtied | 68894 local_blks_written | 0 temp_blks_read | 0 temp_blks_written | 0 blk_read_time | 495425.535999976 blk_write_time | 0 pg_stat_statements
  • 47.
    $ select *from pg_stat_statements; ... query | SELECT "id" FROM run_plan_xact(?) calls | 11165832 total_time | 11743325.6880088 rows | 11165832 blk_read_time | 495425.535999976 blk_write_time | 0 Statements average time in ms $ select (sum(total_time) / sum(calls))::numeric(6,3) from pg_stat_statements; The most writing (to shared_buffers) queries $ select query, shared_blks_dirtied from pg_stat_statements where shared_blks_dirtied > 0 order by 2 desc; pg_stat_statements
  • 48.
    query total time:15:43:07 (14.9%, CPU: 18.2%, IO: 9.0%) сalls: 476 (0.00%) rows: 476,000 avg_time: 118881.54ms (IO: 21.2%) user: app_user db: ustats query: SELECT filepath, type, deviceuid FROM imvevents WHERE state = ?::eventstate AND servertime BETWEEN $1 AND $2 ORDER BY servertime DESC LIMIT $3 OFFSET $4 https://goo.gl/6025wZ Query reports
  • 49.
    query total time:15:43:07 (14.9%, CPU: 18.2%, IO: 9.0%) сalls: 476 (0.00%) rows: 476,000 avg_time: 118881.54ms (IO: 21.2%) user: app_user db: ustats query: SELECT filepath, type, deviceuid FROM imvevents WHERE state = ?::eventstate AND servertime BETWEEN $1 AND $2 ORDER BY servertime DESC LIMIT $3 OFFSET $4 Use sum() for calculating totals. Calculate queries «contribution» in totals. Resource usage (CPU, IO). Query reports
  • 50.
    pg_statio_all_tables, pg_statio_all_indexes. pg_stat_user_functions. Size functions- df *size* pgstattuple (in official contribs package) ● Bloat estimation for tables and indexes. ● Estimation time depends on table (or index) size. pg_buffercache (in official contribs package) ● Shared buffers inspection. ● Heavy performance impact (buffers lock). Behind this talk
  • 51.
    pgfincore (3rd partymodule) ● Low-level operations with tables using mincore(). ● OS page cache inspection. pg_stat_kcache (3rd party module) ● Using getrusage() before and after query. ● CPU usage and real filesystem operations stats. ● Requires pg_stat_statements and postgresql >= 9.4. ● No performance impact. Behind this talk
  • 52.
    ● The abilityto use statistics is useful. ● Statistics are not difficult. ● Statistics help to answer the questions. ● Do experiments. Resume
  • 53.
    Author, write more!! www.blog.postgresql-consulting.com TheStatistics Collector http://www.postgresql.org/docs/current/static/monitoring-stats.html System Administration Functions http://www.postgresql.org/docs/current/static/functions-admin.html Contrib modules http://www.postgresql.org/docs/current/static/pgstatstatements.html http://www.postgresql.org/docs/current/static/pgstattuple.html http://www.postgresql.org/docs/current/static/pgbuffercache.html https://github.com/klando/pgfincore https://github.com/dalibo/pg_stat_kcache SQL utils and sql code examples https://github.com/PostgreSQL-Consulting/pg-utils Unused indexes http://goo.gl/5QxTm4 https://goo.gl/0qXDjl Query reports https://goo.gl/6025wZ Links
  • 54.
    Write Ahead Log Shared Buffers BuffersIO Autovacuum Workers Autovacuum Launcher Background Workers Indexes IO Query Execution Query Planning Client Backends Postmaster Tables IO Logger Process Stats Collector Logical Replication WAL Sender Process Archiver Process Background Writer Checkpointer Process Network Storage Recovery Process WAL Receiver Process Tables/Indexes Data Files pg_stat_all_tables pg_current_xlog_location pg_replication_slots pg_stat_replication pg_stat_archiver pg_stat_database_conflicts pg_buffercache pg_stat_database pg_stat_activity pg_stat_user_tables pg_stat_database pg_stat_bgwrier pgstattuplepg_table_size pg_database_size pg_index_size pg_stat_activity EXPLAIN pg_stat_statements pg_locks pg_stat_user_functions pg_stat_all_indexes pg_stat_database pg_statio_all_tables pg_xlog_location_diff nicstat* iostat* pg_stat_kcache pg_stat_statements Questions