PostgreSQL command line cheatsheet

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## PSQL

Magic words:
```bash
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

## Configuration

- 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 ``` 2) 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 ``` 3) 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;` ## Create command There are many `CREATE` choices, like `CREATE DATABASE __database_name__`, `CREATE TABLE __table_name__` ... Parameters differ but can be checked [at the official documentation](https://www.postgresql.org/search/?u=%2Fdocs%2F9.1%2F&q=CREATE). ## Handy queries - `SELECT * FROM pg_proc WHERE proname='__procedurename__'`: List procedure/function - `SELECT * 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 use - `SELECT pg_size_pretty(pg_database_size('__database_name__'));`: Show DB space in use - `show statement_timeout;`: Show current user's statement timeout - `SELECT * FROM pg_indexes WHERE tablename='__table_name__' AND schemaname='__schema_name__';`: Show table indexes - Get all indexes from all tables of a schema: ```sql 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: ```sql 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): ```sql SELECT * FROM pg_stat_activity WHERE waiting='t' ``` - Currently running queries with process pid: ```sql 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)` or `column::type` - `'__table_name__'::regclass::oid`: Get oid having a table name Query analysis: - `EXPLAIN __query__`: see the query plan for the given query - `EXPLAIN ANALYZE __query__`: see and execute the query plan for the given query - `ANALYZE [__table__]`: collect statistics Generating random data ([source](https://www.citusdata.com/blog/2019/07/17/postgres-tips-for-average-and-power-user/)): - `INSERT INTO some_table (a_float_value) SELECT random() * 100000 FROM generate_series(1, 1000000) i;` Get sizes of tables, indexes and full DBs: ```sql 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](https://www.postgresql.org/docs/9.2/sql-copy.html): Import/export from CSV to tables: ```sql 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 ```sql 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 ```sql 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: ```sql SELECT grantee, privilege_type FROM information_schema.role_table_grants WHERE table_name='name-of-the-table'; ``` - Kill all Connections: ```sql SELECT pg_terminate_backend(pg_stat_activity.pid) FROM pg_stat_activity WHERE datname = current_database() AND pid <> pg_backend_pid(); ``` ## Keyboard shortcuts - `CTRL` + `R`: reverse-i-search ## Tools - `ptop` and `pg_top`: `top` for PG. Available on the APT repository from `apt.postgresql.org`. - [pg_activity](https://github.com/julmon/pg_activity): Command line tool for PostgreSQL server activity monitoring. - [Unix-like reverse search in psql](https://dba.stackexchange.com/questions/63453/is-there-a-psql-equivalent-of-bashs-reverse-search-history): ```bash $ 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;` ## Resources & Documentation - [Postgres Weekly](https://postgresweekly.com/) newsletter: The best way IMHO to keep up to date with PG news - [100 psql Tips](https://mydbanotebook.org/psql_tips_all.html): Name says all, lots of useful tips! - [PostgreSQL Exercises](https://pgexercises.com/): 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](https://severalnines.com/blog/performance-cheat-sheet-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](https://github.com/jberkus/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](https://twitter.com/westermanndanie/status/1242117182982586372))

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