Postgres 15

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create table demo(
    data jsonb not null
);

CREATE TABLE

CREATE INDEX ref_idx ON demo 
  USING gin (data) ;

CREATE INDEX

set enable_seqscan=false

SET

explain analyze select * from demo 
  where jsonb_contains(
   data
  ,
  '[{"answer":"42"}]'::jsonb
  );

QUERY PLAN

Seq Scan on demo  (cost=10000000000.00..10000000027.00 rows=453 width=32) (actual time=0.007..0.007 rows=0 loops=1)

  Filter: jsonb_contains(data, '[{"answer": "42"}]'::jsonb)

Planning Time: 0.146 ms

Execution Time: 0.318 ms

EXPLAIN

explain analyze select * from demo 
  where 
   data
  @>
  '[{"answer":"42"}]'::jsonb
;

QUERY PLAN

Bitmap Heap Scan on demo  (cost=12.11..22.67 rows=14 width=32) (actual time=0.715..0.715 rows=0 loops=1)

  Recheck Cond: (data @> '[{"answer": "42"}]'::jsonb)

  ->  Bitmap Index Scan on ref_idx  (cost=0.00..12.10 rows=14 width=0) (actual time=0.708..0.708 rows=0 loops=1)

        Index Cond: (data @> '[{"answer": "42"}]'::jsonb)

Planning Time: 0.836 ms

Execution Time: 0.766 ms

EXPLAIN