Postgres 15

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select setseed(.42);--stabilise `random()` between re-runs
--generate samples
create table tbl as 
select (random()*1e3)::int as id
     , initcap((--https://www.randomlists.com/things?show_images=false&dup=false&qty=200
          array['USB drive','deodorant','sailboat','bowl','pencil','bottle cap','scotch tape','water bottle','bananas','cell phone','shampoo','lotion','shawl','teddies','sponge','floor','lamp shade','greeting card','cookie jar','flag','sun glasses','headphones','controller','buckle','flowers','clock','rubber duck','ring','mirror','fake flowers','bow','spring','magnet','knife','soda can','lip gloss','cup','white out','desk','food','chapter book','candy wrapper','nail file','screw','drill press','sketch pad','computer','bag','thermometer','clay pot','rubber band','chair','canvas','hair tie','pen','chalk','piano','ice cube tray','seat belt','blouse','zipper','cinder block','outlet','remote','plastic fork','stockings','shovel','puddle','key chain','sofa','monitor','tomato','helmet','beef','face wash','stop sign','clothes','video games','model car','bookmark','house','button','packing peanuts','thermostat','bed','fork','mouse pad','sticky note','pool stick','leg warmers','street lights','apple','charger','air freshener','keys','window','sharpie','photo album','slipper','clamp','thread','bracelet','newspaper','twezzers','needle','soap','wallet','box','pillow','rusty nail','door','spoon','glow stick','shirt','eye liner','book','sidewalk','toothbrush','phone','glasses','ipod','keyboard','nail clippers','checkbook','bread','cat','coasters','pants','speakers','carrots','twister','paper','credit card','towel','CD','money','socks','tv','tire swing','toilet','plate','bottle','playing card','picture frame','grid paper','camera','mp3 player','toe ring','car','candle','tooth picks','radio','hair brush','truck','sand paper','lace','conditioner','vase','purse','paint brush','tissue box','eraser','shoes','milk','toothpaste','cork','chocolate','fridge','lamp','doll','soy sauce packet','wagon','watch','mop','balloon','shoe lace','perfume','drawer','sandal','boom box','table','hanger','rug','blanket','couch','television','washing machine','brocolli','tree','glass'
               ])[(1+random()*189)::int]) as product
     , (random()*1e3)::numeric(6,1)::numeric as cost
from generate_series(1,3e5);
--inspect samples
select * from tbl tablesample bernoulli(.42)repeatable(.42)limit 6;

setseed

SELECT 1

SELECT 300000

id
product
cost

551
Bow
705.9

896
Sofa
31.9

635
Mouse Pad
213.6

543
Lamp Shade
623.0

954
Scotch Tape
603.9

797
Scotch Tape
336.7

SELECT 6

vacuum analyze tbl;

VACUUM

select attname as column_name
      ,(most_common_vals::text::text[])[:5] as sample
from pg_stats
where tablename='tbl';

column_name
sample

id
{866,77,760,812,419}

product
{"Rubber Band",Bread,Twister,"Model Car",Knife}

cost
{430.0,960.5,474.8,575.3,705.8}

SELECT 3

explain analyze 
select attname as column_name
      ,(most_common_vals::text::text[])[:5]
from pg_stats
where tablename='tbl';

QUERY PLAN

Subquery Scan on pg_stats  (cost=4.85..23.31 rows=1 width=96) (actual time=0.047..0.071 rows=3 loops=1)

  ->  Nested Loop  (cost=4.85..23.29 rows=1 width=401) (actual time=0.038..0.053 rows=3 loops=1)

        Join Filter: (has_column_privilege(c.oid, a.attnum, 'select'::text) AND (c.oid = a.attrelid))

        ->  Nested Loop  (cost=4.57..21.76 rows=2 width=180) (actual time=0.027..0.032 rows=3 loops=1)

              ->  Index Scan using pg_class_relname_nsp_index on pg_class c  (cost=0.27..8.29 rows=1 width=8) (actual time=0.010..0.011 rows=1 loops=1)

                    Index Cond: (relname = 'tbl'::name)

                    Filter: ((NOT relrowsecurity) OR (NOT row_security_active(oid)))

              ->  Bitmap Heap Scan on pg_statistic s  (cost=4.30..13.44 rows=3 width=176) (actual time=0.010..0.013 rows=3 loops=1)

                    Recheck Cond: (starelid = c.oid)

                    Heap Blocks: exact=2

                    ->  Bitmap Index Scan on pg_statistic_relid_att_inh_index  (cost=0.00..4.30 rows=3 width=0) (actual time=0.006..0.006 rows=3 loops=1)

                          Index Cond: (starelid = c.oid)

        ->  Index Scan using pg_attribute_relid_attnum_index on pg_attribute a  (cost=0.28..0.74 rows=1 width=70) (actual time=0.003..0.003 rows=1 loops=3)

              Index Cond: ((attrelid = s.starelid) AND (attnum = s.staattnum))

              Filter: (NOT attisdropped)

Planning Time: 0.773 ms

Execution Time: 0.127 ms

EXPLAIN
id	product	cost
551	Bow	705.9
896	Sofa	31.9
635	Mouse Pad	213.6
543	Lamp Shade	623.0
954	Scotch Tape	603.9
797	Scotch Tape	336.7
column_name	sample
id	{866,77,760,812,419}
product	{"Rubber Band",Bread,Twister,"Model Car",Knife}
cost	{430.0,960.5,474.8,575.3,705.8}