Postgres 12

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Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.

select version();

version

PostgreSQL 12.2 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.3.1 20190507 (Red Hat 8.3.1-4), 64-bit

SELECT (20 * random())::INTEGER AS rand FROM generate_series(1, 10);

rand

1

11

20

15

6

3

18

16

9

16

SELECT MD5(random()::TEXT) FROM GENERATE_SERIES(1, 5);

md5

c7d5006b7f6a85fc01286d28de9ccfc0

0b9421ecc3649cd50ffc14e25a1ce112

d875bcc955eeb938f24270ec249c7cc2

4a877bc0cb574d5177f5b37d04932359

8c26474ddf84ce5b56f290bf11cec74b

  SELECT chr((65 + round(random() * 25)) :: integer) 
  FROM generate_series(1, 10)

chr

J

I

J

L

F

P

U

O

U

L

SELECT REGEXP_REPLACE('ABC12345xyz','[[:digit:]]','','g');

regexp_replace

ABCxyz

WITH cte AS
(
  SELECT MD5(random()::TEXT) AS rand FROM GENERATE_SERIES(1, 5)
)
SELECT REGEXP_REPLACE(rand,'[[:digit:]]','','g') AS letters FROM cte

letters

efcdeff

ebacffebfdecadaf

deccdfafbfed

cdecea

dbebcafba