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chore(postgres): dump acquired knowledge

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This commit is contained in:
Michele Cereda
2024-10-03 09:00:41 +02:00
parent ec54344455
commit 151ff0f0f8
5 changed files with 91 additions and 4 deletions
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5
knowledge base/acronyms and abbreviations.md
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@@ -38,7 +38,8 @@
| CSS | Cascading Style Sheets | |
| CVE | Common Vulnerabilities and Exposures | |
| CVS | Concurrent Versioning System | |
| DBMS | Data Base Management System | |
| DB | Data Base | |
| DBMS | DB Management System | |
| DDL | Data Definition Language | |
| DKIM | DomainKeys Identified Mail | |
| DML | Data Manipulation Language | |
@@ -79,6 +80,7 @@
| LED | Light Emitting Diode | |
| LIFO | Last In First Out | |
| M2COTS | Mass Market COTS | Widely available COTS products |
| MR | Merge Request | Prevalently used in GitLab |
| NACL | Network ACL | |
| OAM | [Open Application Model] | |
| OAM | Operations, Administration and Management | |
@@ -89,6 +91,7 @@
| PEBCAK | Problem Exists Between Chair And Keyboard | |
| PGP | Pretty Good Privacy | |
| PII | Personally Identifiable Information | |
| PR | Pull Request | Prevalently used in GitHub |
| RBAC | Role-Based Access Control | |
| ROM | Read-Only Memory | |
| RPM | Revolutions Per Minute | |

0
snippets/postgresql.sh → snippets/postgres/commands.sh
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54
snippets/postgres/functions.sql Normal file
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@@ -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
**/

34
snippets/postgresql.sql → snippets/postgres/primer.sql
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@@ -1,3 +1,8 @@
-- Single line comment
/*
* multi-line comment
*/
-- Add '+' to psql commands to get more information
@@ -249,6 +254,11 @@ 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
@@ -283,6 +293,24 @@ SELECT setseed(0.25), round(random()::DECIMAL, 15) AS random_number; -- seed mu
-- Functions
-- Refer <https://www.postgresql.org/docs/current/sql-createfunction.html>
CREATE OR REPLACE FUNCTION return_1() RETURNS integer
LANGUAGE SQL
RETURN 1;
\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');

2
snippets/systemd.sh
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@@ -7,3 +7,5 @@ sudo hostnamectl
sudo hostnamectl status --static
sudo hostnamectl set-hostname --pretty 'prometheus'
sudo systemctl list-units --state='failed'