Postgres 16

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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?.

CREATE TABLE "test"(
	"arr" text[]
);

CREATE TABLE

insert into "test" (
  "arr"
)
values 
  ('{"10000", "10000", "10000", "10000"}')
  ,(array['100','200','300'])
  ,(array['400','500','600'])
  ,(array['100','200','600']);

INSERT 0 4

select "arr" from "test";

arr

{10000,10000,10000,10000}

{100,200,300}

{400,500,600}

{100,200,600}

SELECT 4

CREATE TABLE "testUnique"(
	"unique" text
);

CREATE TABLE

insert into "testUnique" (
  "unique"
)
values 
   ('10000')
  ,('100')
  ,('200')
  ,('300')
  ,('400')
  ,('500')
  ,('600');

INSERT 0 7

select "unique" from "testUnique";

unique

10000

100

200

300

400

500

600

SELECT 7