How can the backend_start be greater than 2 days of xact_start/query_start? The 3rd sessions looks good, but the first 2 looks weird, is this possible? Would this mean anything?
pg=> select * from pg_catalog.pg_stat_activity where usename = 'etl_user' and state = 'active' and backend_xmin = 65201266;
datid | datname | pid |usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | xact_start | query_start | state_change | wait_event_type | wait_event| state | backend_xid | backend_xmin | query | backend_type
-------+---------+-------+----------+----------+------------------------+----------------+-----------------+-------------+-------------------------------+-------------------------------+-------------------------------+-------------------------------+-----------------+------------+--------+-------------+--------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-----------------
16408 | pg| 37908 | 229661 | etl_user | PostgreSQL JDBC Driver | | | | 2021-04-20 21:36:22.540271+00 | 2021-04-17 22:31:32.314106+00 | 2021-04-17 22:31:32.317577+00 | 2021-04-20 21:36:22.541472+00 | || active | | 65201266 | SELECT 1 FROM (SELECT ...) | parallel worker
16408 | pg| 37909 | 229661 | etl_user | PostgreSQL JDBC Driver | | | | 2021-04-20 21:36:22.540909+00 | 2021-04-17 22:31:32.314106+00 | 2021-04-17 22:31:32.317577+00 | 2021-04-20 21:36:22.542134+00 | || active | | 65201266 | SELECT 1 FROM (SELECT ...) | parallel worker
16408 | pg| 3601 | 229661 | etl_user | PostgreSQL JDBC Driver | 10.175.130.142 | | 49832 | 2021-04-17 22:31:32.232008+00 | 2021-04-17 22:31:32.314106+00 | 2021-04-17 22:31:32.317577+00 | 2021-04-17 22:31:32.317578+00 | || active | | 65201266 | SELECT 1 FROM (SELECT ...) | client backend
(3 rows)
It looks to me like those are parallel workers started up to help the leader, and they inherit the leaders xact_start, but not backend_start. It would help to see the rest of the columns in pg_stat_activity, and know the version.
Yes, that looks impossible.
The only explanation that I have is that someone changed the system time since the sessions started.
Related
We have had an incredibly long running autovacuum process running on one of our smaller database machines that we believe has been using a lot of Aurora:StorageIOUsage:
We determined this by running SELECT * FROM pg_stat_activity WHERE wait_event_type = 'IO';
and seeing the below results repeatedly.
datid | datname | pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | xact_start | query_start | state_change | wait_event_type | wait_event | state | backend_xid | backend_xmin | query | backend_type
--------+----------------------------+-------+----------+-----------+------------------+----------------+-----------------+-------------+-------------------------------+-------------------------------+-------------------------------+-------------------------------+-----------------+--------------+--------+-------------+--------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------------
398954 | postgres | 17582 | | | | | | | 2022-09-29 18:45:55.364654+00 | 2022-09-29 18:46:20.253107+00 | 2022-09-29 18:46:20.253107+00 | 2022-09-29 18:46:20.253108+00 | IO | DataFileRead | active | | 66020718 | autovacuum: VACUUM pg_catalog.pg_depend | autovacuum worker
398954 | postgres | 17846 | | | | | | | 2022-09-29 18:46:04.092536+00 | 2022-09-29 18:46:29.196309+00 | 2022-09-29 18:46:29.196309+00 | 2022-09-29 18:46:29.19631+00 | IO | DataFileRead | active | | 66020732 | autovacuum: VACUUM pg_toast.pg_toast_2618 | autovacuum worker
As you can see from the screenshot it has been going for well over a month, and is mainly for the pg_depend, pg_attribute, and pg_toast_2618 tables which are not all that large. I haven't been able to find any reason why these tables would need so much vacuuming other than maybe a database restore from our production environment (this is one of our lower environments). Here are the pg_stat_sys_tables entries for those tables and the pg_rewrite which is the table that pg_toast_2618 is associated with:
relid | schemaname | relname | seq_scan | seq_tup_read | idx_scan | idx_tup_fetch | n_tup_ins | n_tup_upd | n_tup_del | n_tup_hot_upd | n_live_tup | n_dead_tup | n_mod_since_analyze | last_vacuum | last_autovacuum | last_analyze | last_autoanalyze | vacuum_count | autovacuum_count | analyze_count | autoanalyze_count
-------+------------+---------------+----------+--------------+----------+---------------+-----------+-----------+-----------+---------------+------------+------------+---------------------+-------------+-------------------------------+--------------+-------------------------------+--------------+------------------+---------------+-------------------
1249 | pg_catalog | pg_attribute | 185251 | 12594432 | 31892996 | 119366792 | 1102817 | 3792 | 1065737 | 1281 | 543392 | 1069529 | 23584 | | 2022-09-29 18:53:25.227334+00 | | 2022-09-28 01:12:47.628499+00 | 0 | 1266763 | 0 | 36
2608 | pg_catalog | pg_depend | 2429 | 369003445 | 14152628 | 23494712 | 7226948 | 0 | 7176855 | 0 | 476267 | 7176855 | 0 | | 2022-09-29 18:52:34.523257+00 | | 2022-09-28 02:02:52.232822+00 | 0 | 950137 | 0 | 71
2618 | pg_catalog | pg_rewrite | 25 | 155083 | 1785288 | 1569100 | 64127 | 314543 | 62472 | 59970 | 7086 | 377015 | 13869 | | 2022-09-29 18:53:11.288732+00 | | 2022-09-23 18:54:50.771969+00 | 0 | 1280018 | 0 | 81
2838 | pg_toast | pg_toast_2618 | 0 | 0 | 1413436 | 3954640 | 828571 | 0 | 825143 | 0 | 15528 | 825143 | 1653714 | | 2022-09-29 18:52:47.242386+00 | | | 0 | 608881 | 0 | 0
I'm pretty new to Postgres and I'm wondering what could possibly cause this level of records to need to be cleaned up, and why it would take well over a month to accomplish considering we always have autovacuum set to TRUE. We are running Postgres version 10.17 on a single db.t3.medium, and the only thing I can think of at this point is to try increasing the instance size. Do we simply need to increase our database instance size on our aurora cluster so that this can be done more in memory? I'm at a bit of a loss for how to reduce this huge sustained spike in Storage IO costs.
Additional information for our autovaccum settings:
=> SELECT * FROM pg_catalog.pg_settings WHERE name LIKE '%autovacuum%';
name | setting | unit | category | short_desc | extra_desc | context | vartype | source | min_val | max_val | enumvals | boot_val | reset_val | sourcefile | sourceline | pending_restart
-------------------------------------+-----------+------+-------------------------------------+-------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------+------------+---------+--------------------+---------+------------+-----------------------------------------------------------------------------------------+-----------+-----------+-----------------------------------+------------+-----------------
autovacuum | on | | Autovacuum | Starts the autovacuum subprocess. | | sighup | bool | configuration file | | | | on | on | /rdsdbdata/config/postgresql.conf | 78 | f
autovacuum_analyze_scale_factor | 0.05 | | Autovacuum | Number of tuple inserts, updates, or deletes prior to analyze as a fraction of reltuples. | | sighup | real | configuration file | 0 | 100 | | 0.1 | 0.05 | /rdsdbdata/config/postgresql.conf | 55 | f
autovacuum_analyze_threshold | 50 | | Autovacuum | Minimum number of tuple inserts, updates, or deletes prior to analyze. | | sighup | integer | default | 0 | 2147483647 | | 50 | 50 | | | f
autovacuum_freeze_max_age | 200000000 | | Autovacuum | Age at which to autovacuum a table to prevent transaction ID wraparound. | | postmaster | integer | default | 100000 | 2000000000 | | 200000000 | 200000000 | | | f
autovacuum_max_workers | 3 | | Autovacuum | Sets the maximum number of simultaneously running autovacuum worker processes. | | postmaster | integer | configuration file | 1 | 262143 | | 3 | 3 | /rdsdbdata/config/postgresql.conf | 45 | f
autovacuum_multixact_freeze_max_age | 400000000 | | Autovacuum | Multixact age at which to autovacuum a table to prevent multixact wraparound. | | postmaster | integer | default | 10000 | 2000000000 | | 400000000 | 400000000 | | | f
autovacuum_naptime | 5 | s | Autovacuum | Time to sleep between autovacuum runs. | | sighup | integer | configuration file | 1 | 2147483 | | 60 | 5 | /rdsdbdata/config/postgresql.conf | 9 | f
autovacuum_vacuum_cost_delay | 5 | ms | Autovacuum | Vacuum cost delay in milliseconds, for autovacuum. | | sighup | integer | configuration file | -1 | 100 | | 20 | 5 | /rdsdbdata/config/postgresql.conf | 73 | f
autovacuum_vacuum_cost_limit | -1 | | Autovacuum | Vacuum cost amount available before napping, for autovacuum. | | sighup | integer | default | -1 | 10000 | | -1 | -1 | | | f
autovacuum_vacuum_scale_factor | 0.1 | | Autovacuum | Number of tuple updates or deletes prior to vacuum as a fraction of reltuples. | | sighup | real | configuration file | 0 | 100 | | 0.2 | 0.1 | /rdsdbdata/config/postgresql.conf | 22 | f
autovacuum_vacuum_threshold | 50 | | Autovacuum | Minimum number of tuple updates or deletes prior to vacuum. | | sighup | integer | default | 0 | 2147483647 | | 50 | 50 | | | f
autovacuum_work_mem | -1 | kB | Resource Usage / Memory | Sets the maximum memory to be used by each autovacuum worker process. | | sighup | integer | default | -1 | 2147483647 | | -1 | -1 | | | f
log_autovacuum_min_duration | -1 | ms | Reporting and Logging / What to Log | Sets the minimum execution time above which autovacuum actions will be logged. | Zero prints all actions. -1 turns autovacuum logging off. | sighup | integer | default | -1 | 2147483647 | | -1 | -1 | | | f
rds.force_autovacuum_logging_level | disabled | | Customized Options | Emit autovacuum log messages irrespective of other logging configuration. | Each level includes all the levels that follow it.Set to disabled to disable this feature and fall back to using log_min_messages. | sighup | enum | default | | | {debug5,debug4,debug3,debug2,debug1,info,notice,warning,error,log,fatal,panic,disabled} | disabled | disabled | | | f
I would say you have some very long-lived snapshot being held. These tables need to be vacuumed, but the vacuum doesn't accomplish anything because the dead tuples can't be removed as some old snapshot still can see them. So immediately after being vacuumed, they are still eligible to be vacuumed again. So it tries again every 5 seconds (autovacuum_naptime), because autovacuum doesn't have a way to say "Don't bother until this snapshot which blocked me from accomplishing anything last time goes away"
Check pg_stat_activity for very old 'idle in transaction' and for any prepared transactions.
I am using Ubuntu Linux. I am trying to use Postgres as database. It is doing fine when I created a user:
CREATE USER username;
But when I try to create a database, it returns nothing:
CREATE DATABASE databasename;
What is happening with my Postgres?
datid | datname | pid | leader_pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | xact_start | query_start | state_change | wait_event_type | wait_event | state | backend_xid | backend_xmin | query_id | query | backend_type
-------+----------+------+------------+----------+----------+------------------+-------------+-----------------+-------------+-------------------------------+-------------------------------+-------------------------------+-------------------------------+-----------------+---------------------+--------+-------------+--------------+----------+---------------------------------+------------------------------
| | 8237 | | | | | | | | 2022-02-02 13:00:47.683187+07 | | | | Activity | AutoVacuumMain | | | | | | autovacuum launcher
| | 8239 | | 10 | postgres | | | | | 2022-02-02 13:00:47.70127+07 | | | | Activity | LogicalLauncherMain | | | | | | logical replication launcher
13726 | postgres | 8329 | | 10 | postgres | psql | | | -1 | 2022-02-02 13:08:52.250244+07 | 2022-02-02 13:09:10.651383+07 | 2022-02-02 13:09:10.651383+07 | 2022-02-02 13:09:10.651393+07 | Lock | object | active | | 740 | | CREATE DATABASE kong; | client backend
13726 | postgres | 8313 | | 10 | postgres | psql | | | -1 | 2022-02-02 13:04:57.265085+07 | 2022-02-02 13:10:40.097817+07 | 2022-02-02 13:10:40.097817+07 | 2022-02-02 13:10:40.09782+07 | | | active | | 740 | | SELECT * FROM pg_stat_activity; | client backend
| | 8235 | | | | | | | | 2022-02-02 13:00:47.664058+07 | | | | Activity | BgWriterHibernate | | | | | | background writer
| | 8234 | | | | | | | | 2022-02-02 13:00:47.654713+07 | | | | Activity | CheckpointerMain | | | | | | checkpointer
| | 8236 | | | | | | | | 2022-02-02 13:00:47.673631+07 | | | | Activity | WalWriterMain | | | | | | walwriter
(7 rows)
(END)
and for the pg_locks
locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted | fastpath | waitstart
------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+------+------------------+---------+----------+-------------------------------
relation | 13726 | 12290 | | | | | | | | 7/17 | 8313 | AccessShareLock | t | t |
virtualxid | | | | | 7/17 | | | | | 7/17 | 8313 | ExclusiveLock | t | t |
virtualxid | | | | | 3/15 | | | | | 3/15 | 8329 | ExclusiveLock | t | t |
virtualxid | | | | | 6/12 | | | | | 6/12 | 8335 | ExclusiveLock | t | t |
virtualxid | | | | | 5/3 | | | | | 5/3 | 8266 | ExclusiveLock | t | t |
virtualxid | | | | | 4/1 | | | | | 4/1 | 8264 | ExclusiveLock | t | t |
object | 0 | | | | | | 1262 | 1 | 0 | 6/12 | 8335 | RowExclusiveLock | f | f | 2022-02-02 13:09:30.561821+07
object | 0 | | | | | | 1262 | 1 | 0 | 3/15 | 8329 | ShareLock | f | f | 2022-02-02 13:09:10.651571+07
object | 0 | | | | | | 1262 | 1 | 0 | 4/1 | 8264 | RowExclusiveLock | t | f |
relation | 0 | 1262 | | | | | | | | 3/15 | 8329 | AccessShareLock | t | f |
object | 0 | | | | | | 1262 | 1 | 0 | 5/3 | 8266 | RowExclusiveLock | t | f |
(11 rows)
(END)
Database info
postgres=# \l
Name | Owner | Encoding | Collate | Ctype | Access privileges | Size | Tablespace | Description
-----------+----------+----------+---------+---------+-----------------------+---------+------------+--------------------------------------------
postgres | postgres | UTF8 | C.UTF-8 | C.UTF-8 | | 8529 kB | pg_default | default administrative connection database
template0 | postgres | UTF8 | C.UTF-8 | C.UTF-8 | =c/postgres +| 8377 kB | pg_default | unmodifiable empty database
| | | | | postgres=CTc/postgres | | |
template1 | postgres | UTF8 | C.UTF-8 | C.UTF-8 | =c/postgres +| 8529 kB | pg_default | default template for new databases
| | | | | postgres=CTc/postgres | | |
(3 rows)
postgres=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------------------+-----------
kong | | {}
postgres | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
postgres=#
Using the same database name and user is not good practice. This may result in various errors.
When you call the command
CREATE DATABASE databaseName;
PostgreSql creates a database. This may take some time. After creating the database, you will receive a message:
CREATE DATABASE
postgres=#
Problem solved by reinstalling the pg to its old version (was installed 14, downgrade to 12 and it solved). Thanks to everyone here who helped me
SELECT relation::regclass, * FROM pg_locks ;
Results in the following:
relation | locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted | fastpath
----------+------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+------+-----------------+---------+----------
pg_locks | relation | 16397 | 11187 | | | | | | | | 76/111628 | 2652 | AccessShareLock | t | t
| virtualxid | | | | | 76/111628 | | | | | 76/111628 | 2652 | ExclusiveLock | t | t
(2 rows)
Can I assume that my query of pg_locks is itself what is causing the ExclusiveLock in that result?
Im trying to create index on large table:
datid | datname | pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | xact_start | query_start | state_change | waiting | state | backend_xid | backend_xmin | query
-------+----------------------+-------+----------+-------------------------+--- --------------------------+--------------+-----------------+-------------+------ -------------------------+-------------------------------+---------------------- ---------+-------------------------------+---------+--------+-------------+----- ---------+---------------------------------------------------------------------- ---------------------
25439 | messengerdb | 30692 | 25438 | messengerdb_rw | pgAdmin III - Przegl??darka | 10.167.12.52 | | 50593 | 2016-08-11 05:27:12.101452+02 | 2016-08-11 05:28:01.535943+02 | 2016-08-11 05:28:01.535943+02 | 2016-08-11 05:28:01.535958+02 | t | active | | 1173740991 | CREATE INDEX CONCURRENTLY user_time_idx +
| | | | | | | | | | | | | | | | | ON core.conversations (user_id ASC NULLS LAST, last_message_timestamp ASC NULLS LAST);+
Is this query working? I'm worried about 'waiting' column === 't' does it mean that it is waiting for lock or sth?
Creating an index concurrently may take a long time since it does not lock the table from writes and it waits until other transactions are finished. However, it may wait forever if you have connections that stay idle in transactions (for example when a client or application keeps an open connection without rollback/commit).
Check if there are some idle connections in transactions (you should be able to see them in the processes list). You can also check PostgreSQL logs.
Section about creating index concurrently in PostgreSQL documentation can be helpful. There is also a nice article about concurrent indexes under this link.
I am trying to run a CREATE INDEX CONCURRENTLY command against a Postgres 9.2 database. I implemented a MigrationResolver as shown in issue 655. When this migration step is run via mvn flyway:migrate or similar, the command starts but hangs in waiting mode.
I verified that the command is executing via the pg_stat_activity table:
test_2015_04_13_110536=# select * from pg_stat_activity;
datid | datname | pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | xact_start | query_start | state_change | waiting | state | query
-------+------------------------+-------+----------+----------+------------------+-------------+-----------------+-------------+-------------------------------+-------------------------------+-------------------------------+-------------------------------+---------+---------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
21095 | test_2015_04_13_110536 | 56695 | 16385 | postgres | psql | | | -1 | 2015-04-13 11:10:01.127768-06 | 2015-04-13 11:13:08.936651-06 | 2015-04-13 11:13:08.936651-06 | 2015-04-13 11:13:08.936655-06 | f | active | select * from pg_stat_activity;
21095 | test_2015_04_13_110536 | 56824 | 16385 | postgres | | 127.0.0.1 | | 52437 | 2015-04-13 11:12:55.438927-06 | 2015-04-13 11:12:55.476442-06 | 2015-04-13 11:12:55.487139-06 | 2015-04-13 11:12:55.487175-06 | f | idle in transaction | SELECT "version_rank","installed_rank","version","description","type","script","checksum","installed_on","installed_by","execution_time","success" FROM "public"."schema_version" ORDER BY "version_rank"
21095 | test_2015_04_13_110536 | 56825 | 16385 | postgres | | 127.0.0.1 | | 52438 | 2015-04-13 11:12:55.443687-06 | 2015-04-13 11:12:55.49024-06 | 2015-04-13 11:12:55.49024-06 | 2015-04-13 11:12:55.490241-06 | t | active | CREATE UNIQUE INDEX CONCURRENTLY person_restrict_duplicates_2_idx ON person(name, person_month, person_year)
(3 rows)
An example project that replicates this problem can be found in my github: chrisphelps/flyway-experiment
My suspicion is that the flyway query against schema version which is idle in transaction is preventing postgres from proceeding with the index creation.
How can I resolve the conflict so that postgres will proceed with the migration? Has anyone been able to apply this sort of migration to postgres via flyway?
In the meantime, there is a Resolver included in flyway which looks for some magic in the filename.
Just add the prefix 'NT' (for No-Transaction) to your migration file, i. e.
V01__usual_migration_1.sql
V02__another_migration.sql
NTV03__migration_that_does_not_run_in_transaction.sql
V04__classical_migration_4.sql
etc.