PostgreSQL command line cheatsheet

postgres-cheatsheet.md

PSQL - 00000001

Magic words:

psql -U postgres

If run with -E flag, it will describe the underlaying queries of the \ commands (cool for learning!).

Most \d commands support additional param of __schema__.name__ and accept wildcards like *.*

• \q: Quit/Exit
• \c __database__: Connect to a database
• \d __table__: Show table definition including triggers
• \dt *.*: List tables from all schemas (if *.* is omitted will only show SEARCH_PATH ones)
• \l: List databases
• \dn: List schemas
• \df: List functions
• \dv: List views
• \df+ __function__ : Show function SQL code.
• \x: Pretty-format query results instead of the not-so-useful ASCII tables

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__.

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 '

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:

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;

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

Tools

• pg-top: top for PG. sudo apt-get install ptop + pg_top
• Unix-like reverse search in psql:

$ echo "bind "^R" em-inc-search-prev" > $HOME/.editrc
$ source $HOME/.editrc

Postgres Cheatsheet - 00000002

This is a collection of the most common commands I run while administering Postgres databases. The variables shown between the open and closed tags, "<" and ">", should be replaced with a name you choose. Postgres has multiple shortcut functions, starting with a forward slash, "". Any SQL command that is not a shortcut, must end with a semicolon, ";". You can use the keyboard UP and DOWN keys to scroll the history of previous commands you've run.

Setup

installation, Ubuntu

http://www.postgresql.org/download/linux/ubuntu/ https://help.ubuntu.com/community/PostgreSQL

sudo echo "deb http://apt.postgresql.org/pub/repos/apt/ wily-pgdg main" > \
  /etc/apt/sources.list.d/pgdg.list
wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
sudo apt-get update
sudo apt-get install -y postgresql-9.5 postgresql-client-9.5 postgresql-contrib-9.5

sudo su - postgres
psql

connect

http://www.postgresql.org/docs/current/static/app-psql.html

psql

psql -U <username> -d <database> -h <hostname>

psql --username=<username> --dbname=<database> --host=<hostname>

disconnect

\q
\!

clear the screen

(CTRL + L)

info

\conninfo

configure

http://www.postgresql.org/docs/current/static/runtime-config.html

sudo nano $(locate -l 1 main/postgresql.conf)
sudo service postgresql restart

debug logs

# print the last 24 lines of the debug log
sudo tail -24 $(find /var/log/postgresql -name 'postgresql-*-main.log')

Recon

show version

SHOW SERVER_VERSION;

show system status

\conninfo

show environmental variables

SHOW ALL;

list users

SELECT rolname FROM pg_roles;

show current user

SELECT current_user;

show current user's permissions

\du

list databases

\l

show current database

SELECT current_database();

show all tables in database

\dt

list functions

\df <schema>

Databases

list databasees

\l

connect to database

\c <database_name>

show current database

SELECT current_database();

create database

http://www.postgresql.org/docs/current/static/sql-createdatabase.html

CREATE DATABASE <database_name> WITH OWNER <username>;

delete database

http://www.postgresql.org/docs/current/static/sql-dropdatabase.html

DROP DATABASE IF EXISTS <database_name>;

rename database

http://www.postgresql.org/docs/current/static/sql-alterdatabase.html

ALTER DATABASE <old_name> RENAME TO <new_name>;

Users

list roles

SELECT rolname FROM pg_roles;

create user

http://www.postgresql.org/docs/current/static/sql-createuser.html

CREATE USER <user_name> WITH PASSWORD '<password>';

drop user

http://www.postgresql.org/docs/current/static/sql-dropuser.html

DROP USER IF EXISTS <user_name>;

alter user password

http://www.postgresql.org/docs/current/static/sql-alterrole.html

ALTER ROLE <user_name> WITH PASSWORD '<password>';

Permissions

become the postgres user, if you have permission errors

sudo su - postgres
psql

grant all permissions on database

http://www.postgresql.org/docs/current/static/sql-grant.html

GRANT ALL PRIVILEGES ON DATABASE <db_name> TO <user_name>;

grant connection permissions on database

GRANT CONNECT ON DATABASE <db_name> TO <user_name>;

grant permissions on schema

GRANT USAGE ON SCHEMA public TO <user_name>;

grant permissions to functions

GRANT EXECUTE ON ALL FUNCTIONS IN SCHEMA public TO <user_name>;

grant permissions to select, update, insert, delete, on a all tables

GRANT SELECT, UPDATE, INSERT ON ALL TABLES IN SCHEMA public TO <user_name>;

grant permissions, on a table

GRANT SELECT, UPDATE, INSERT ON <table_name> TO <user_name>;

grant permissions, to select, on a table

GRANT SELECT ON ALL TABLES IN SCHEMA public TO <user_name>;

Schema

list schemas

\dn

SELECT schema_name FROM information_schema.schemata;

SELECT nspname FROM pg_catalog.pg_namespace;

create schema

http://www.postgresql.org/docs/current/static/sql-createschema.html

CREATE SCHEMA IF NOT EXISTS <schema_name>;

drop schema

http://www.postgresql.org/docs/current/static/sql-dropschema.html

DROP SCHEMA IF EXISTS <schema_name> CASCADE;

Tables

list tables, in current db

\dt

SELECT table_schema,table_name FROM information_schema.tables ORDER BY table_schema,table_name;

list tables, globally

\dt *.*.

SELECT * FROM pg_catalog.pg_tables

list table schema

\d <table_name>
\d+ <table_name>

SELECT column_name, data_type, character_maximum_length
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = '<table_name>';

create table

http://www.postgresql.org/docs/current/static/sql-createtable.html

CREATE TABLE <table_name>(
  <column_name> <column_type>,
  <column_name> <column_type>
);

create table, with an auto-incrementing primary key

CREATE TABLE <table_name> (
  <column_name> SERIAL PRIMARY KEY
);

delete table

http://www.postgresql.org/docs/current/static/sql-droptable.html

DROP TABLE IF EXISTS <table_name> CASCADE;

Columns

add column

http://www.postgresql.org/docs/current/static/sql-altertable.html

ALTER TABLE <table_name> IF EXISTS
ADD <column_name> <data_type> [<constraints>];

update column

ALTER TABLE <table_name> IF EXISTS
ALTER <column_name> TYPE <data_type> [<constraints>];

delete column

ALTER TABLE <table_name> IF EXISTS
DROP <column_name>;

update column to be an auto-incrementing primary key

ALTER TABLE <table_name>
ADD COLUMN <column_name> SERIAL PRIMARY KEY;

insert into a table, with an auto-incrementing primary key

INSERT INTO <table_name>
VALUES (DEFAULT, <value1>);


INSERT INTO <table_name> (<column1_name>,<column2_name>)
VALUES ( <value1>,<value2> );

Data

read all data

http://www.postgresql.org/docs/current/static/sql-select.html

SELECT * FROM <table_name>;

read one row of data

SELECT * FROM <table_name> LIMIT 1;

search for data

SELECT * FROM <table_name> WHERE <column_name> = <value>;

insert data

http://www.postgresql.org/docs/current/static/sql-insert.html

INSERT INTO <table_name> VALUES( <value_1>, <value_2> );

edit data

http://www.postgresql.org/docs/current/static/sql-update.html

UPDATE <table_name>
SET <column_1> = <value_1>, <column_2> = <value_2>
WHERE <column_1> = <value>;

delete all data

http://www.postgresql.org/docs/current/static/sql-delete.html

DELETE FROM <table_name>;

delete specific data

DELETE FROM <table_name>
WHERE <column_name> = <value>;

Scripting

run local script, on remote host

http://www.postgresql.org/docs/current/static/app-psql.html

psql -U <username> -d <database> -h <host> -f <local_file>

psql --username=<username> --dbname=<database> --host=<host> --file=<local_file>

backup database data, everything

http://www.postgresql.org/docs/current/static/app-pgdump.html

pg_dump <database_name>

pg_dump <database_name>

backup database, only data

pg_dump -a <database_name>

pg_dump --data-only <database_name>

backup database, only schema

pg_dump -s <database_name>

pg_dump --schema-only <database_name>

restore database data

http://www.postgresql.org/docs/current/static/app-pgrestore.html

pg_restore -d <database_name> -a <file_pathway>

pg_restore --dbname=<database_name> --data-only <file_pathway>

restore database schema

pg_restore -d <database_name> -s <file_pathway>

pg_restore --dbname=<database_name> --schema-only <file_pathway>

export table into CSV file

http://www.postgresql.org/docs/current/static/sql-copy.html

\copy <table_name> TO '<file_path>' CSV

export table, only specific columns, to CSV file

\copy <table_name>(<column_1>,<column_1>,<column_1>) TO '<file_path>' CSV

import CSV file into table

http://www.postgresql.org/docs/current/static/sql-copy.html

\copy <table_name> FROM '<file_path>' CSV

import CSV file into table, only specific columns

\copy <table_name>(<column_1>,<column_1>,<column_1>) FROM '<file_path>' CSV

Debugging

http://www.postgresql.org/docs/current/static/using-explain.html

http://www.postgresql.org/docs/current/static/runtime-config-logging.html

Advanced Features

http://www.tutorialspoint.com/postgresql/postgresql_constraints.htm

Ruby on Rails

ActiveRecord::Base.connection.execute(<<-SQL
  UPDATE coaches
  SET
    preferences->>'current_sport' = preferences->>'initcap(current_sport)'
  SQL
)