chore(postgres): dump acquired knowledge

2026-02-09 13:44:24 +00:00 · 2024-10-03 09:00:41 +02:00
parent ec54344455
commit 151ff0f0f8
5 changed files with 91 additions and 4 deletions
--- a/snippets/postgres/commands.sh
+++ b/snippets/postgres/commands.sh
@@ -0,0 +1,48 @@
+#!/usr/bin/env sh
+
+# Start DBs
+docker run --rm --name 'postgres' -d -p '5432:5432' -e POSTGRES_PASSWORD='password' 'postgres:14.12'
+
+# Connect to DBs
+psql 'postgres'
+psql 'postgres' 'admin'
+psql --host 'prod.db.lan' --port '5432' --username 'postgres' --database 'postgres' --password
+psql -h 'host.fqnd' -p '5432' -U 'admin' -d 'postgres' -W
+psql 'postgresql://localhost:5433/games?sslmode=require'
+psql 'host=host.fqdn port=5467 user=admin dbname=postgres'
+
+# List available databases
+psql … --list
+
+# Change passwords
+psql … -U 'jonathan' -c '\password'
+psql … -U 'admin' -c '\password jonathan'
+
+# Execute SQL commands
+psql … -c 'select * from tableName;' -o 'out.file'
+psql … -c 'select * from tableName;' -H
+psql … -f 'commands.sql'
+psql … -f 'dump.sql' -e
+
+# Dump DBs
+pg_dump --host 'host.fqnd' --port '5432' --username 'postgres' --dbname 'postgres' --password
+pg_dump -h 'host.fqnd' -p '5432' -U 'admin' -d 'postgres' -W
+pg_dump -U 'postgres' -d 'sales' -F 'custom' -f 'sales.bak' --schema-only
+pg_dump … -T 'customers,orders' -t 'salespeople,performances'
+pg_dump … -s --format 'custom'
+
+# Dump DBs' schema only
+pg_dump --host 'host.fqnd' --port '5432' --username 'postgres' --dbname 'postgres' --password --schema-only
+pg_dump -h 'host.fqnd' -p '5432' -U 'admin' -d 'postgres' -Ws
+
+# Dump users and groups to file
+pg_dumpall -h 'host.fqnd' -p '5432' -U 'postgres' -l 'postgres' -W --roles-only --file 'roles.sql'
+pg_dumpall -h 'host.fqnd' -p '5432' -U 'postgres' -l 'postgres' -Wrf 'roles.sql' --no-role-passwords
+
+# Restore backups
+pg_restore -U 'postgres' -d 'sales' 'sales.dump'
+pg_restore -h 'host.fqdn' -U 'master' -d 'sales' -Oxj 8 'sales.dump'
+
+# Initialize a test DB
+pgbench -i 'test-db'
+pgbench -i 'test-db' -h 'hostname' -p '5555' -U 'user'
--- a/snippets/postgres/functions.sql
+++ b/snippets/postgres/functions.sql
@@ -0,0 +1,54 @@
+/**
+ * Shuffle values in a column
+ * Returns the number of affected rows
+ *
+ * Only works on that column, with no regards for data connections.
+ * Requires a way to identify the row in the source table during the update.
+ * └── Using 'ctid' over a table's primary key to avoid the need of specifying another column.
+ * ctids shall stay the same, but values shall be numbered randomly (hence the shuffling part).
+ *
+ * Credits to <https://stackoverflow.com/questions/33555524/postgresql-shuffle-column-values#33555639>.
+ *
+ * SELECT user_id, name FROM band_members WHERE name IN ('mark', 'tom', 'travis') ORDER BY name;
+ * SELECT shuffle_column('band_members','name');
+ * SELECT user_id, name FROM band_members WHERE name IN ('mark', 'tom', 'travis') ORDER BY name;
+ **/
+
+CREATE OR REPLACE FUNCTION shuffle_column(
+  table_name TEXT,
+  column_name TEXT
+)
+RETURNS INTEGER
+LANGUAGE plpgsql
+AS $$
+  DECLARE affected_rows INTEGER;
+  BEGIN
+    EXECUTE format('
+      WITH
+        ctids AS (
+          SELECT
+            ROW_NUMBER() OVER (),
+            ctid
+          FROM %I
+        ),
+        shuffled_values AS (
+          SELECT
+            ROW_NUMBER() OVER (ORDER BY RANDOM()),
+            %I AS new_value
+          FROM %I
+        )
+      UPDATE %I
+        SET %I = shuffled_values.new_value
+        FROM shuffled_values JOIN ctids ON shuffled_values.row_number = ctids.row_number
+        WHERE %I.ctid = ctids.ctid
+    ', table_name, column_name, table_name, table_name, column_name, table_name);
+    GET DIAGNOSTICS affected_rows = ROW_COUNT;
+    RETURN affected_rows;
+  END;
+$$;
+
+
+/**
+ * Replace UUID in a column
+ * Returns the number of affected rows
+ **/
--- a/snippets/postgres/primer.sql
+++ b/snippets/postgres/primer.sql
@@ -0,0 +1,316 @@
+-- Single line comment
+/*
+ * multi-line comment
+ */
+
+-- Add '+' to psql commands to get more information
+
+
+-- Show help
+help
+
+-- Show available SQL commands
+\h
+
+-- Show available psql commands
+\?
+
+
+-- Show PostgreSQL version
+SELECT version();
+
+-- Show connection information
+\conninfo
+
+
+-- Load extensions globally in the instance
+-- If supported (no RDS)
+ALTER SYSTEM SET shared_preload_libraries = 'anon';
+ALTER DATABASE postgres SET session_preload_libraries = 'anon';
+
+
+-- List databases
+\l
+\list+
+SELECT datname FROM pg_database;
+
+-- Create databases
+CREATE DATABASE world;
+
+-- Show database settings
+SELECT * FROM pg_settings;
+SELECT "name", "setting" FROM pg_settings WHERE NAME LIKE '%log%';
+SHOW "wal_keep_size";
+SHOW "password_encryption";
+SHOW "pgaudit.log";
+
+-- Change database settings *for the current session* only
+SET pgaudit.log = none;
+SET password_encryption = scram-sha-256;
+
+-- Change database settings permanently
+-- Will *not* be active for the current session, logout and login again to see the change
+ALTER DATABASE reviser SET pgaudit.log TO none;
+
+-- Switch between databases
+\c sales
+\connect vendor
+
+
+-- List schemas
+\dn
+SELECT schema_name FROM information_schema.schemata;
+SELECT nspname FROM pg_catalog.pg_namespace;
+
+-- Create schemas
+CREATE SCHEMA mundane;
+CREATE SCHEMA IF NOT EXISTS mundane AUTHORIZATION joe;
+
+-- Remove schemas
+DROP SCHEMA mundane;
+DROP SCHEMA IF EXISTS mundane CASCADE;
+
+
+-- List tables
+\d
+\dt
+\dt+
+
+-- Create tables
+CREATE TABLE people (
+  id          char(2)      PRIMARY KEY,
+  first_name  varchar(40)  NOT NULL,
+  last_name   text(40)     NOT NULL,
+  phone       varchar(20)
+);
+
+-- Show table structure
+\d sales
+\d+ clients
+SELECT column_name, data_type, character_maximum_length FROM INFORMATION_SCHEMA.COLUMNS WHERE table_name = 'vendors';
+
+
+-- Insert data
+INSERT INTO people(id, first_name, last_name, phone)
+VALUES
+  ('T1', 'Sarah', 'Conor', '0609110911'),
+  ('wa', 'Wally', 'Polly', null);
+
+
+-- Revoke *default* privileges
+ALTER DEFAULT PRIVILEGES IN SCHEMA cache REVOKE select ON TABLES FROM sales;
+ALTER DEFAULT PRIVILEGES FOR ROLE juan IN SCHEMA cache REVOKE all ON TABLES FROM sales;
+
+
+-- List users with respective roles
+\du
+\du+
+-- List users only
+SELECT usename FROM pg_catalog.pg_user;
+-- List roles only
+SELECT rolname FROM pg_catalog.pg_roles;
+
+-- Check the current user has SuperUser privileges
+SHOW is_superuser;
+
+-- Create roles
+-- Roles *are* users *and* groups since PostgreSQL vFIXME
+-- Users are just roles that can LOGIN
+-- Does *not* support IF NOT EXISTS
+CREATE ROLE miriam;
+CREATE ROLE miriam WITH LOGIN PASSWORD 'jw8s0F4' VALID UNTIL '2005-01-01';
+CREATE USER mike IN ROLE engineers;
+
+-- Grant roles SuperUser privileges
+-- The role granting privileges must be already SuperUser
+ALTER USER joel WITH SUPERUSER;
+
+-- Revoke SuperUser privileges
+ALTER USER joel WITH NOSUPERUSER;
+
+-- Grant privileges to users
+ALTER USER mark CREATEDB REPLICATION;
+ALTER ROLE miriam CREATEROLE CREATEDB;
+
+-- Change passwords
+ALTER USER mike WITH PASSWORD NULL;
+ALTER USER jonathan WITH PASSWORD 'seagull5-pantomime-Resting';
+ALTER ROLE samantha WITH PASSWORD 'Wing5+Trunks3+Relic2' VALID UNTIL 'August 4 12:00:00 2024 +1';
+
+-- Change password's validity
+ALTER ROLE fred VALID UNTIL 'infinity';
+
+-- Rename roles
+ALTER ROLE manager RENAME TO boss;
+
+-- Assign roles to users
+GRANT rds_superuser TO mike;
+
+-- Remove role memberships from users
+REVOKE engineers FROM mike;
+
+-- List permissions
+-- on tables
+SELECT *
+FROM information_schema.role_table_grants
+WHERE grantee = 'darwin';
+-- about ownership
+SELECT *
+FROM pg_tables
+WHERE tableowner = 'darwin';
+-- on schemas
+SELECT
+  r.usename AS grantor,
+  e.usename AS grantee,
+  nspname,
+  privilege_type,
+  is_grantable
+FROM pg_namespace
+JOIN LATERAL (
+  SELECT *
+  FROM aclexplode(nspacl) AS x
+) a ON true
+JOIN pg_user e ON a.grantee = e.usesysid
+JOIN pg_user r ON a.grantor = r.usesysid
+WHERE e.usename = 'darwin';
+
+
+-- Close the connection to the current DB
+\q
+\quit
+
+
+-- Get passwords
+SELECT rolpassword from pg_authid where rolname = 'admin';
+
+
+-- Show available extensions
+SELECT name FROM pg_available_extensions ORDER BY name;
+
+-- Show installed extensions
+\dx
+SELECT * FROM pg_extension;
+SELECT extname FROM pg_extension ORDER BY extname;
+
+-- Show extensions versions
+SELECT postgis_version(), postgis_full_version(), postgis_lib_version();
+
+-- Add extensions
+CREATE EXTENSION pg_transport;
+CREATE EXTENSION IF NOT EXISTS pgaudit;
+
+-- Remove extensions
+DROP EXTENSION plpgsql;
+DROP EXTENSION IF EXISTS plpgsql, btree_gist, … CASCADE;
+
+
+-- Simulate DB transfers
+-- Requires 'pg_transport' to be installed on both the source and destination DBs
+-- Requires 'pg_transport' to be the *only* extension active on the source
+SELECT transport.import_from_server(
+  'up.to.63.chars.source.fqdn', 5432,
+  'source.username', 'source.password', 'source.db',
+  'destination.password',
+  true
+);
+
+-- Run DB transfers
+-- Requires 'pg_transport' to be installed on both the source and destination DBs
+-- Requires 'pg_transport' to be the *only* extension active on the source
+SELECT transport.import_from_server(
+  'up.to.63.chars.source.fqdn', 5432,
+  'source.username', 'source.password', 'source.db',
+  'destination.password',
+  false
+);
+
+
+-- List replication slots
+SELECT * FROM pg_replication_slots;
+
+-- Create replication slots
+-- Requires the executor to be superuser or replication role
+SELECT pg_create_physical_replication_slot('peerflow_slot_prod');
+SELECT pg_create_logical_replication_slot('airbyte_slot', 'pgoutput');
+
+-- Drop replication slots
+SELECT pg_drop_replication_slot('airbyte_slot');
+
+
+-- List publications
+\dRp
+\dRp+
+
+-- Create publications
+CREATE PUBLICATION peerflow_prod FOR ALL TABLES;
+CREATE PUBLICATION airbyte FOR TABLE call_log, queue_log;
+
+
+-- Wildcards
+-- '%' = zero or more characters
+-- '_' = exactly 1 character
+SELECT * FROM users WHERE name LIKE '% Banda';  -- ends with ' Banda'
+SELECT name FROM customers WHERE name LIKE '%banda%';  -- contains 'banda'
+SELECT id FROM customers WHERE City LIKE 'L___on';  -- starts with 'L', followed by any 3 characters, followed by 'on'
+
+
+-- Comparison with lists
+SELECT * FROM users WHERE username IN ('matthew', 'lucas', 'todd', 'roxy', 'kyle', 'ken', 'gideon');
+SELECT * FROM users WHERE username NOT IN ('knives', 'wallace');
+
+
+-- Shuffle data
+-- source: https://stackoverflow.com/questions/33555524/postgresql-shuffle-column-values#33555639
+WITH
+  ids AS (
+    SELECT
+      row_number() OVER (ORDER BY random()) row_num,
+      vendor_id AS new_vendor_id
+    FROM vendors
+  ),
+  names AS (
+    SELECT
+      row_number() OVER (ORDER BY random()) row_num,
+      vendor_name AS new_vendor_name
+    FROM vendors
+  )
+UPDATE vendors
+  SET
+    vendor_id = new_vendor_id,
+    vendor_name = new_vendor_name
+  FROM ids JOIN names ON ids.row_num = names.row_num
+  WHERE vendor_id = new_vendor_id;
+
+
+-- Deterministic random values
+SELECT setseed(0.25), round(random()::DECIMAL, 15) AS random_number;  -- seed must be in [-1:1]
+
+
+-- Search values in all tables
+-- source: https://stackoverflow.com/questions/5350088/how-to-search-a-specific-value-in-all-tables-postgresql/23036421#23036421
+--         └── https://github.com/dverite/postgresql-functions/tree/master/global_search
+
+
+-- Functions
+-- Refer <https://www.postgresql.org/docs/current/sql-createfunction.html>
+\df
+\df+ to_char
+SELECT routine_name FROM information_schema.routines WHERE routine_type = 'FUNCTION';
+SELECT p.proname FROM pg_catalog.pg_namespace n JOIN pg_catalog.pg_proc p ON p.pronamespace = n.oid WHERE p.prokind = 'f';
+
+CREATE OR REPLACE FUNCTION return_1() RETURNS INTEGER LANGUAGE SQL RETURN 1;
+
+
+-- Type casting
+SELECT
+  CAST ('21' AS INTEGER), 420.69::INTEGER,
+  CAST('100' AS DOUBLE PRECISION), '100.93'::FLOAT,
+  CAST ('true' AS BOOLEAN),
+  CAST('2024-02-01 12:34:56' AS DATE), '01-OCT-2015' ::DATE,
+  CAST('2016-11-11' AS TIMESTAMP), '2016-11-11'::TIMESTAMP,
+  CAST ('15 minute' AS INTERVAL), '3 month' :: INTERVAL,
+  CAST ('20 days' AS TEXT), '24 hour':: TEXT,
+  CAST (ARRAY[1,3,5] AS TEXT),
+  '{1,2,3}'::INTEGER[] AS result_array;
+SELECT to_char(42, '0000');  -- '0042'
+SELECT to_number('12,454.9', '99G999D9S');