Magic words:
psql -U postgres
Some interesting flags (to see all, use -h
or --help
depending on your psql version):
-E
: will describe the underlaying queries of the\
commands (cool for learning!)-l
: psql will list all databases and then exit (useful if the user you connect with doesn't has a default database, like at AWS RDS)
Most \d
commands support additional param of __schema__.name__
and accept wildcards like *.*
\?
: Show help (list of available commands with an explanation)\q
: Quit/Exit\c __database__
: Connect to a database\d __table__
: Show table definition (columns, etc.) including triggers\d+ __table__
: More detailed table definition including description and physical disk size\l
: List databases\dy
: List events\df
: List functions\di
: List indexes\dn
: List schemas\dt *.*
: List tables from all schemas (if*.*
is omitted will only show SEARCH_PATH ones)\dT+
: List all data types\dv
: List views\dx
: List all extensions installed\df+ __function__
: Show function SQL code.\x
: Pretty-format query results instead of the not-so-useful ASCII tables\copy (SELECT * FROM __table_name__) TO 'file_path_and_name.csv' WITH CSV
: Export a table as CSV\des+
: List all foreign servers\dE[S+]
: List all foreign tables\! __bash_command__
: execute__bash_command__
(e.g.\! ls
)
User Related:
\du
: List users\du __username__
: List a username if present.create role __test1__
: Create a role with an existing username.create role __test2__ noinherit login password __passsword__;
: Create a role with username and password.set role __test__;
: Change role for current session to__test__
.grant __test2__ to __test1__;
: Allow__test1__
to set its role as__test2__
.\deu+
: List all user mapping on server
- Service management commands:
sudo service postgresql stop
sudo service postgresql start
sudo service postgresql restart
- Changing verbosity & querying Postgres log:
1) First edit the config file, set a decent verbosity, save and restart postgres:
sudo vim /etc/postgresql/9.3/main/postgresql.conf
# Uncomment/Change inside:
log_min_messages = debug5
log_min_error_statement = debug5
log_min_duration_statement = -1
sudo service postgresql restart
- Now you will get tons of details of every statement, error, and even background tasks like VACUUMs
tail -f /var/log/postgresql/postgresql-9.3-main.log
- How to add user who executed a PG statement to log (editing
postgresql.conf
):
log_line_prefix = '%t %u %d %a '
-
Check Extensions enabled in postgres:
SELECT * FROM pg_extension;
-
Show available extensions:
SELECT * FROM pg_available_extension_versions;
There are many CREATE
choices, like CREATE DATABASE __database_name__
, CREATE TABLE __table_name__
... Parameters differ but can be checked at the official documentation.
SELECT * FROM pg_proc WHERE proname='__procedurename__'
: List procedure/functionSELECT * FROM pg_views WHERE viewname='__viewname__';
: List view (including the definition)SELECT pg_size_pretty(pg_total_relation_size('__table_name__'));
: Show DB table space in useSELECT pg_size_pretty(pg_database_size('__database_name__'));
: Show DB space in useshow statement_timeout;
: Show current user's statement timeoutSELECT * FROM pg_indexes WHERE tablename='__table_name__' AND schemaname='__schema_name__';
: Show table indexes- Get all indexes from all tables of a schema:
SELECT
t.relname AS table_name,
i.relname AS index_name,
a.attname AS column_name
FROM
pg_class t,
pg_class i,
pg_index ix,
pg_attribute a,
pg_namespace n
WHERE
t.oid = ix.indrelid
AND i.oid = ix.indexrelid
AND a.attrelid = t.oid
AND a.attnum = ANY(ix.indkey)
AND t.relnamespace = n.oid
AND n.nspname = 'kartones'
ORDER BY
t.relname,
i.relname
- Execution data:
- Queries being executed at a certain DB:
SELECT datname, application_name, pid, backend_start, query_start, state_change, state, query
FROM pg_stat_activity
WHERE datname='__database_name__';
- Get all queries from all dbs waiting for data (might be hung):
SELECT * FROM pg_stat_activity WHERE waiting='t'
- Currently running queries with process pid:
SELECT
pg_stat_get_backend_pid(s.backendid) AS procpid,
pg_stat_get_backend_activity(s.backendid) AS current_query
FROM (SELECT pg_stat_get_backend_idset() AS backendid) AS s;
- Get Connections by Database:
SELECT datname, numbackends FROM pg_stat_database;
Casting:
CAST (column AS type)
orcolumn::type
'__table_name__'::regclass::oid
: Get oid having a table name
Query analysis:
EXPLAIN __query__
: see the query plan for the given queryEXPLAIN ANALYZE __query__
: see and execute the query plan for the given queryANALYZE [__table__]
: collect statistics
Generating random data (source):
INSERT INTO some_table (a_float_value) SELECT random() * 100000 FROM generate_series(1, 1000000) i;
Get sizes of tables, indexes and full DBs:
select current_database() as database,
pg_size_pretty(total_database_size) as total_database_size,
schema_name,
table_name,
pg_size_pretty(total_table_size) as total_table_size,
pg_size_pretty(table_size) as table_size,
pg_size_pretty(index_size) as index_size
from ( select table_name,
table_schema as schema_name,
pg_database_size(current_database()) as total_database_size,
pg_total_relation_size(table_name) as total_table_size,
pg_relation_size(table_name) as table_size,
pg_indexes_size(table_name) as index_size
from information_schema.tables
where table_schema=current_schema() and table_name like 'table_%'
order by total_table_size
) as sizes;
- COPY command: Import/export from CSV to tables:
COPY table_name [ ( column_name [, ...] ) ]
FROM { 'filename' | STDIN }
[ [ WITH ] ( option [, ...] ) ]
COPY { table_name [ ( column_name [, ...] ) ] | ( query ) }
TO { 'filename' | STDOUT }
[ [ WITH ] ( option [, ...] ) ]
- List all grants for a specific user
SELECT table_catalog, table_schema, table_name, privilege_type
FROM information_schema.table_privileges
WHERE grantee = 'user_to_check' ORDER BY table_name;
- List all assigned user roles
SELECT
r.rolname,
r.rolsuper,
r.rolinherit,
r.rolcreaterole,
r.rolcreatedb,
r.rolcanlogin,
r.rolconnlimit,
r.rolvaliduntil,
ARRAY(SELECT b.rolname
FROM pg_catalog.pg_auth_members m
JOIN pg_catalog.pg_roles b ON (m.roleid = b.oid)
WHERE m.member = r.oid) as memberof,
r.rolreplication
FROM pg_catalog.pg_roles r
ORDER BY 1;
- Check permissions in a table:
SELECT grantee, privilege_type
FROM information_schema.role_table_grants
WHERE table_name='name-of-the-table';
- Kill all Connections:
SELECT pg_terminate_backend(pg_stat_activity.pid)
FROM pg_stat_activity
WHERE datname = current_database() AND pid <> pg_backend_pid();
CTRL
+R
: reverse-i-search
ptop
andpg_top
:top
for PG. Available on the APT repository fromapt.postgresql.org
.- pg_activity: Command line tool for PostgreSQL server activity monitoring.
- Unix-like reverse search in psql:
$ echo "bind "^R" em-inc-search-prev" > $HOME/.editrc
$ source $HOME/.editrc
- Show IP of the DB Instance:
SELECT inet_server_addr();
- File to save PostgreSQL credentials and permissions (format:
hostname:port:database:username:password
):chmod 600 ~/.pgpass
- Collect statistics of a database (useful to improve speed after a Database Upgrade as previous query plans are deleted):
ANALYZE VERBOSE;
- To obtain the
CREATE TABLE
query of a table, any visual GUI like pgAdmin allows to easily, but else you can usepg_dump
, e.g.:pg_dump -t '<schema>.<table>' --schema-only <database>
(source)
- Operations Cheat Sheet: Official PG wiki cheat sheet with an amazing amount of explanations of many topics, features, and many many internal implementation details
- Postgres Weekly newsletter: The best way IMHO to keep up to date with PG news
- 100 psql Tips: Name says all, lots of useful tips!
- PostgreSQL Exercises: An awesome resource to learn to learn SQL, teaching you with simple examples in a great visual way. Highly recommended.
- A Performance Cheat Sheet for PostgreSQL: Great explanations of
EXPLAIN
,EXPLAIN ANALYZE
,VACUUM
, configuration parameters and more. Quite interesting if you need to tune-up a postgres setup. - annotated.conf: Annotations of all 269 postgresql.conf settings for PostgreSQL 10.
psql -c "\l+" -H -q postgres > out.html
: Generate a html report of your databases (source: Daniel Westermann)
Very nice tips! Thank you