Hello Julien, On 9/17/21 4:00 PM, Julien Rouhaud wrote:
Hi, On Fri, Sep 17, 2021 at 9:55 PM <ramikvl@xxxxxxxxx> wrote: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?Yes, because doing an index scan on a table containing a single row is an order or magnitude less efficient than simply doing a sequential scan. You should try to simulate something close to your production data to see something interesting.
Thank you for the tip. I've tried to generate more data. I have 2000 rows in the table but the query still uses sequential scan.
Seq Scan on api (cost=0.00..131.00 rows=2000 width=64) (actual time=0.005..0.959 rows=2000 loops=1)
Filter: ((jdoc -> 'tags'::text) ? 'qui'::text) Planning Time: 0.064 ms Execution Time: 1.027 ms Any thoughts?
