SET client_min_messages = warning;
CREATE EXTENSION IF NOT EXISTS vector;
SET enable_seqscan = off;
CREATE UNLOGGED TABLE t (val vector(3));
INSERT INTO t (val) VALUES ('[0,0,0]'), ('[1,2,3]'), ('[1,1,1]'), (NULL);
CREATE INDEX ON t USING ivfflat (val) WITH (lists = 1);
SELECT * FROM t ORDER BY val <-> '[3,3,3]';
   val   
---------
 [1,2,3]
 [1,1,1]
 [0,0,0]
(3 rows)

DROP TABLE t;