PostgreSQL – informacje o bazie

1. list of table indexes:
SELECT
tablename,
indexname,
indexdef
FROM
pg_indexes
WHERE
schemaname = ‚public’

\d table_name

2. DB & tables related

  • \q: Quit/Exit
  • \c __database__: Connect to a database
  • \d __table__: Show table definition 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
  • \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

3. 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__.

4. Service management commands:

sudo service postgresql stop
sudo service postgresql start
sudo service postgresql restart

5. 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
  1. 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
  1. How to add user who executed a PG statement to log (editing postgresql.conf):
log_line_prefix = '%t %u %d %a '

6. SQL 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
  • 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;

7. Casting:

  • CAST (column AS type) or column::type
  • '__table_name__'::regclass::oid: Get oid having a table name

8. 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

9. Generating random data (source):

  • INSERT INTO some_table (a_float_value) SELECT random() * 100000 FROM generate_series(1, 1000000) i;

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