Create USER_GUIDE.md
Ibrar Ahmed
GitHub
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## User Guide
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pg_stat_monitor extension contains a view called pg_stat_monitor, which contains all the monitoring information. Following is the list of columns in pg_stat_monitor.
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| Column | Type | pg_stat_monitor | pg_stat_statments
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|--------------------|--------------------------|----------------------|------------------
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bucket | integer | :heavy_check_mark: | :x:
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bucket_start_time | timestamp with time zone | :heavy_check_mark: | :x:
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userid | oid | :heavy_check_mark: | :heavy_check_mark:
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dbid | oid | :heavy_check_mark: | :heavy_check_mark:
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client_ip | inet | :heavy_check_mark: | :x:
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queryid | text | :heavy_check_mark: | :heavy_check_mark:
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query | text | :heavy_check_mark: | :heavy_check_mark:
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application_name | text | :heavy_check_mark: | :x:
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relations | text[] | :heavy_check_mark: | :x:
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cmd_type | text[] | :heavy_check_mark: | :x:
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elevel | integer | :heavy_check_mark: | :x:
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sqlcode | integer | :heavy_check_mark: | :x:
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message | text | :heavy_check_mark: | :x:
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plans | bigint | :heavy_check_mark: | :heavy_check_mark:
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plan_total_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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plan_min_timei | double precision | :heavy_check_mark: | :heavy_check_mark:
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plan_max_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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plan_mean_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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plan_stddev_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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calls | bigint | :heavy_check_mark: | :heavy_check_mark:
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total_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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min_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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max_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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mean_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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stddev_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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rows | bigint | :heavy_check_mark: | :heavy_check_mark:
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shared_blks_hit | bigint | :heavy_check_mark: | :heavy_check_mark:
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shared_blks_read | bigint | :heavy_check_mark: | :heavy_check_mark:
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shared_blks_dirtied | bigint | :heavy_check_mark: | :heavy_check_mark:
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shared_blks_written | bigint | :heavy_check_mark: | :heavy_check_mark:
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local_blks_hit | bigint | :heavy_check_mark: | :heavy_check_mark:
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local_blks_read | bigint | :heavy_check_mark: | :heavy_check_mark:
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local_blks_dirtied | bigint | :heavy_check_mark: | :heavy_check_mark:
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local_blks_written | bigint | :heavy_check_mark: | :heavy_check_mark:
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temp_blks_read | bigint | :heavy_check_mark: | :heavy_check_mark:
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temp_blks_written | bigint | :heavy_check_mark: | :heavy_check_mark:
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blk_read_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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blk_write_time | double precision | :heavy_check_mark: | :heavy_check_mark:
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resp_calls | text[] | :heavy_check_mark: | :x:
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cpu_user_time | double precision | :heavy_check_mark: | :x:
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cpu_sys_time | double precision | :heavy_check_mark: | :x:
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Here are some key features of pg_stat_monitor.
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### Buckets
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pg_stat_monitor collects and aggregates data on a bucket basis. The size of a bucket and the number of buckets should be configured using GUC (Grand Unified Configuration). When a bucket time elapses, pg_stat_monitor resets all the statistics and switches to the next bucket. After the last bucket elapses, pg_stat_monitor goes back to the first bucket. All the data on the first bucket will vanish; therefore, users must read the buckets before that to not lose the data.
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**`bucket`**: Accumulates the statistics per bucket. All the information and aggregate reset for each bucket. The bucket will be a number showing the number of buckets for which this record belongs.
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**`bucket_start_time`**: shows the start time of the bucket.
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```sql
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postgres=# select bucket, bucket_start_time, query from pg_stat_monitor;
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bucket | bucket_start_time | query
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--------+-------------------------------+--------------------------------------------------------
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2 | 2020-05-23 13:24:44.652415+00 | select * from pg_stat_monitor_reset()
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3 | 2020-05-23 13:45:01.55658+00 | select bucket, bucket_start_time, query from pg_stat_monitor
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2 | 2020-05-23 13:24:44.652415+00 | SELECT * FROM foo
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(3 rows)
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```
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### Query Information
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**`userid`**: An ID of the user whom that query belongs. pg_stat_monitor is used to collect queries from all the users; therefore, `userid` is used to segregate the queries based on different users.
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**`dbid`**: The database ID of the query. pg_stat_monitor accumulates queries from all the databases; therefore, this column is used to identify the database.
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**`queryid`**: pg_stat_monitor generates a unique ID for each query (queryid).
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**`query`**: The query column contains the actual text of the query. This parameter depends on the **`pg_stat_monitor.pgsm_normalized_query`** configuration parameters, in which format to show the query.
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**`calls`**: Number of calls of that particular query.
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#### Example 1: Shows the userid, dbid, unique queryid hash, query and total number of calls or that query.
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```sql
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postgres=# select userid, dbid, queryid, substr(query,0, 50) as query, calls from pg_stat_monitor;
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userid | dbid | queryid | query | calls
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--------+-------+------------------+---------------------------------------------------+-------
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10 | 12709 | 214646CE6F9B1A85 | BEGIN | 1577
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10 | 12709 | 8867FEEB8A5388AC | vacuum pgbench_branches | 1
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10 | 12709 | F47D95C9DF863E43 | UPDATE pgbench_branches SET bbalance = bbalance + | 1577
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10 | 12709 | 2FE0A6ABDC20623 | select substr(query,$1, $2) as query, cmd_type fr | 7
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10 | 12709 | A83503D3E1F99139 | select userid, dbid, queryid, substr(query,$1, $ | 1
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10 | 12709 | D4B1243AC3268B9B | select count(*) from pgbench_branches | 1
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10 | 12709 | 2FE0A6ABDC20623 | select substr(query,$1, $2) as query, cmd_type fr | 1
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10 | 12709 | 1D9BDBBCFB89F096 | UPDATE pgbench_accounts SET abalance = abalance + | 1577
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10 | 12709 | 15343084284782B | update test SET a = $1 | 2
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10 | 12709 | 939C2F56E1F6A174 | END | 1577
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1 | 12709 | DAE6D269D27F2EC4 | SELECT FOR UPDATE test SET a = 1; | 1
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10 | 12709 | 2B50C2406BFAC907 | INSERT INTO pgbench_history (tid, bid, aid, delta | 1577
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10 | 12709 | F6DA9838660825CA | vacuum pgbench_tellers | 1
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10 | 12709 | 3AFB8B2452721F9 | SELECT a from test for update | 1
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10 | 12709 | A5CD0AF80D28363 | SELECT abalance FROM pgbench_accounts WHERE aid = | 1577
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10 | 12709 | E445DD36B9189C53 | UPDATE pgbench_tellers SET tbalance = tbalance + | 1577
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10 | 12709 | 4876BBA9A8FCFCF9 | truncate pgbench_history | 1
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10 | 12709 | D3C2299FD9E7348C | select userid, dbid, queryid, query, calls from | 1
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(18 rows)
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```
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#### Example 2: Shows the different username for the queries.
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```
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postgres=# select userid::regrole, datname, substr(query,0, 50) as query, calls from pg_stat_monitor, pg_database WHERE dbid = oid;
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userid | datname | query | calls
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----------+----------+---------------------------------------------------+-------
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vagrant | postgres | select userid::regrole, datname, substr(query,$1, | 1
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vagrant | test_db | insert into bar values($1) | 1
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vagrant | postgres | insert into bar values($1) | 1
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vagrant | test_db | select * from bar | 1
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postgres | postgres | insert into bar values($1) | 1
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(5 rows)
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```
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#### Example 3: Shows the differen database involved in the queries.
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```
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postgres=# select userid::regrole, datname, substr(query,0, 50) as query, calls from pg_stat_monitor, pg_database WHERE dbid = oid;
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userid | datname | query | calls
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---------+----------+---------------------------------------------------+-------
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vagrant | postgres | select userid::regrole, datname, substr(query,$1, | 0
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vagrant | test_db | insert into bar values($1) | 1
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vagrant | test_db | select * from bar | 1
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(3 rows)
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```
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#### Example 4: Shows the connected application_name.
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```sql
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postgres=# select application_name, query from pg_stat_monitor;
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application_name | query
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------------------+------------------------------------------------------------------------------------------------------
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pgbench | UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2
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pgbench | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2
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pgbench | vacuum pgbench_tellers
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pgbench | SELECT abalance FROM pgbench_accounts WHERE aid = $1
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pgbench | END
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pgbench | select count(*) from pgbench_branches
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pgbench | BEGIN
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pgbench | INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES ($1, $2, $3, $4, CURRENT_TIMESTAMP)
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psql | select application_name, query from pg_stat_monitor
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pgbench | vacuum pgbench_branches
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psql | select application_name query from pg_stat_monitor
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pgbench | truncate pgbench_history
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pgbench | UPDATE pgbench_tellers SET tbalance = tbalance + $1 WHERE tid = $2
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(13 rows)
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```
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### Error Messages / Error Codes and Error Level
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**`elevel`**, **`sqlcode`**,**`message`**,: error level / sql code and log/warning/error message
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```sql
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postgres=# select substr(query,0,50) as query, decode_error_level(elevel)as elevel,sqlcode,calls, substr(message,0,50) message from pg_stat_monitor;
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query | elevel | sqlcode | calls | message
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---------------------------------------------------+--------+---------+-------+---------------------------------------------------
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select substr(query,$1,$2) as query, decode_error | | 0 | 1 |
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select bucket,substr(query,$1,$2),decode_error_le | | 0 | 3 |
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| LOG | 0 | 1 | database system is ready to accept connections
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select 1/0; | ERROR | 130 | 1 | division by zero
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| LOG | 0 | 1 | database system was shut down at 2020-11-11 11:37
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select $1/$2 | | 0 | 1 |
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(6 rows)
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```
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### Query Timing Information
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**`total_time`**, **`min_time`**, **`max_time`**, **`mean_time`**: The total / minimum / maximum and mean time spent for the same query.
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```
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postgres=# select userid, total_time, min_time, max_time, mean_time, query from pg_stat_monitor;
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userid | total_time | min_time | max_time | mean_time | query
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--------+--------------------+--------------------+--------------------+--------------------+------------------------------------------------------------------
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10 | 0.14 | 0.14 | 0.14 | 0.14 | select * from pg_stat_monitor_reset()
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10 | 0.19 | 0.19 | 0.19 | 0.19 | select userid, dbid, queryid, query from pg_stat_monitor
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10 | 0.30 | 0.13 | 0.16 | 0.15 | select bucket, bucket_start_time, query from pg_stat_monitor
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10 | 0.29 | 0.29 | 0.29 | 0.29 | select userid, dbid, queryid, query, calls from pg_stat_monitor
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10 | 11277.79 | 11277.79 | 11277.79 | 11277.79 | SELECT * FROM foo
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```
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### Client IP address
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**`client_ip`**: The IP address of the client that originated the query.
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```sql
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postgres=# select userid::regrole, datname, substr(query,0, 50) as query, calls,client_ip from pg_stat_monitor, pg_database WHERE dbid = oid;
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userid | datname | query | calls | client_ip
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---------+----------+---------------------------------------------------+-------+-----------
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vagrant | postgres | UPDATE pgbench_branches SET bbalance = bbalance + | 1599 | 10.0.2.15
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vagrant | postgres | select userid::regrole, datname, substr(query,$1, | 5 | 10.0.2.15
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vagrant | postgres | UPDATE pgbench_accounts SET abalance = abalance + | 1599 | 10.0.2.15
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vagrant | postgres | select userid::regrole, datname, substr(query,$1, | 1 | 127.0.0.1
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vagrant | postgres | vacuum pgbench_tellers | 1 | 10.0.2.15
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vagrant | postgres | SELECT abalance FROM pgbench_accounts WHERE aid = | 1599 | 10.0.2.15
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vagrant | postgres | END | 1599 | 10.0.2.15
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vagrant | postgres | select count(*) from pgbench_branches | 1 | 10.0.2.15
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vagrant | postgres | BEGIN | 1599 | 10.0.2.15
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vagrant | postgres | INSERT INTO pgbench_history (tid, bid, aid, delta | 1599 | 10.0.2.15
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vagrant | postgres | vacuum pgbench_branches | 1 | 10.0.2.15
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vagrant | postgres | truncate pgbench_history | 1 | 10.0.2.15
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vagrant | postgres | UPDATE pgbench_tellers SET tbalance = tbalance + | 1599 | 10.0.2.15
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```
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### Call Timings Histogram
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**`resp_calls`**: Call histogram
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```sql
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postgres=# select resp_calls, query from pg_stat_monitor;
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resp_calls | query
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--------------------------------------------------+----------------------------------------------
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{1," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 0"} | select client_ip, query from pg_stat_monitor
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{3," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 1"} | select * from pg_stat_monitor_reset()
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{3," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 0"," 1"} | SELECT * FROM foo
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```
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There are 10 timebase buckets of the time **`pg_stat_monitor.pgsm_respose_time_step`** in the field ``resp_calls``. The value in the field shows how many queries run in that period of time.
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### Object Information.
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**`relations`**: The list of tables involved in the query
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#### Example 1: List all the table names involved in the query.
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```sql
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postgres=# select relations::oid[]::regclass[], query from pg_stat_monitor;
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relations | query
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--------------------+------------------------------------------------------------------------------------------------------
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{pgbench_accounts} | UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2
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{pgbench_accounts} | SELECT abalance FROM pgbench_accounts WHERE aid = $1
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{pg_stat_monitor} | select relations::oid[]::regclass[], cmd_type,resp_calls,query from pg_stat_monitor
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{pgbench_branches} | select count(*) from pgbench_branches
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{pgbench_history} | INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES ($1, $2, $3, $4, CURRENT_TIMESTAMP)
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{foo,bar} | select * from foo,bar
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(5 rows)
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```
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#### Example 2: List all the views and the name of table in the view. Here we have a view "test_view"
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```sql
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postgres=# \d+ test_view
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View "public.test_view"
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Column | Type | Collation | Nullable | Default | Storage | Description
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--------+---------+-----------+----------+---------+---------+-------------
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foo_a | integer | | | | plain |
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bar_a | integer | | | | plain |
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View definition:
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SELECT f.a AS foo_a,
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b.a AS bar_a
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FROM foo f,
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bar b;
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```
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Now when we query the pg_stat_monitor, it will shows the view name and also all the table names in the view.
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```sql
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postgres=# select relations::oid[]::regclass[], query from pg_stat_monitor;
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relations | query
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---------------------+------------------------------------------------------------------------------------------------------
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{test_view,foo,bar} | select * from test_view
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{foo,bar} | select * from foo,bar
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(2 rows)
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```
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### Query command Type (SELECT, INSERT, UPDATE OR DELETE)
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**`cmd_type`**: List the command type of the query.
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```sql
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postgres=# select substr(query,0, 50) as query, cmd_type from pg_stat_monitor where elevel = 0;
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query | cmd_type
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---------------------------------------------------+-----------------
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BEGIN | {INSERT}
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vacuum pgbench_branches | {}
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UPDATE pgbench_branches SET bbalance = bbalance + | {UPDATE,SELECT}
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select substr(query,$1, $2) as query, cmd_type fr | {SELECT}
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select count(*) from pgbench_branches | {SELECT}
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select substr(query,$1, $2) as query, cmd_type fr | {}
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UPDATE pgbench_accounts SET abalance = abalance + | {UPDATE,SELECT}
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update test SET a = $1 | {UPDATE}
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END | {INSERT}
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INSERT INTO pgbench_history (tid, bid, aid, delta | {INSERT}
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vacuum pgbench_tellers | {}
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SELECT a from test for update | {UPDATE,SELECT}
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SELECT abalance FROM pgbench_accounts WHERE aid = | {SELECT}
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UPDATE pgbench_tellers SET tbalance = tbalance + | {UPDATE,SELECT}
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truncate pgbench_history | {}
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(15 rows)
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```
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## Copyright Notice
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Copyright (c) 2006 - 2020, Percona LLC.
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