jsonb Indexing

[ramikvl@xxxxxxxxx]

Hello,

I'm new to jsonb feature of postgres. I have PostgreSQL 13.2 running 
locally in docker.

I've been playing a little bit with jsonb indexes described 
https://www.postgresql.org/docs/13/datatype-json.html#JSON-INDEXING and 
I'm not able make the GIN index work on 'tags'.

I was wondering what I'm doing wrong. There are steps what I've tried:

CREATE TABLE api (
    jdoc jsonb
);

INSERT INTO api (jdoc)
    VALUES ('{
    "guid": "9c36adc1-7fb5-4d5b-83b4-90356a46061a",
    "name": "Angela Barton",
    "is_active": true,
    "company": "Magnafone",
    "address": "178 Howard Place, Gulf, Washington, 702",
    "registered": "2009-11-07T08:53:22 +08:00",
    "latitude": 19.793713,
    "longitude": 86.513373,
    "tags": [
        "enim",
        "aliquip",
        "qui"
    ]
}');

CREATE INDEX idxgintags ON api USING GIN ((jdoc->'tags'));

EXPLAIN ANALYZE SELECT jdoc->'guid', jdoc->'name' FROM api WHERE jdoc -> 
'tags' ? 'qui';

And the result is

Seq Scan on api  (cost=0.00..1.02 rows=1 width=64) (actual 
time=0.019..0.021 rows=1 loops=1)
  Filter: ((jdoc -> 'tags'::text) ? 'qui'::text)

Planning Time: 0.115 ms

Execution Time: 0.047 ms

Do you know why Index Scan on idxgintag is not used?

Thank you,

Vlasta