SET enable_seqscan = off;
-- L2
CREATE TABLE t (val halfvec(3));
INSERT INTO t (val) VALUES ('[0,0,0]'), ('[1,2,3]'), ('[1,1,1]'), (NULL);
CREATE INDEX ON t USING ivfflat (val halfvec_l2_ops) WITH (lists = 1);
INSERT INTO t (val) VALUES ('[1,2,4]');
SELECT * FROM t ORDER BY val <-> '[3,3,3]';
   val   
---------
 [1,2,3]
 [1,2,4]
 [1,1,1]
 [0,0,0]
(4 rows)

SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <-> (SELECT NULL::halfvec)) t2;
 count 
-------
     4
(1 row)

SELECT COUNT(*) FROM t;
 count 
-------
     5
(1 row)

TRUNCATE t;
NOTICE:  ivfflat index created with little data
DETAIL:  This will cause low recall.
HINT:  Drop the index until the table has more data.
SELECT * FROM t ORDER BY val <-> '[3,3,3]';
 val 
-----
(0 rows)

DROP TABLE t;
-- inner product
CREATE TABLE t (val halfvec(3));
INSERT INTO t (val) VALUES ('[0,0,0]'), ('[1,2,3]'), ('[1,1,1]'), (NULL);
CREATE INDEX ON t USING ivfflat (val halfvec_ip_ops) WITH (lists = 1);
INSERT INTO t (val) VALUES ('[1,2,4]');
SELECT * FROM t ORDER BY val <#> '[3,3,3]';
   val   
---------
 [1,2,4]
 [1,2,3]
 [1,1,1]
 [0,0,0]
(4 rows)

SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <#> (SELECT NULL::halfvec)) t2;
 count 
-------
     4
(1 row)

DROP TABLE t;
-- cosine
CREATE TABLE t (val halfvec(3));
INSERT INTO t (val) VALUES ('[0,0,0]'), ('[1,2,3]'), ('[1,1,1]'), (NULL);
CREATE INDEX ON t USING ivfflat (val halfvec_cosine_ops) WITH (lists = 1);
INSERT INTO t (val) VALUES ('[1,2,4]');
SELECT * FROM t ORDER BY val <=> '[3,3,3]';
   val   
---------
 [1,1,1]
 [1,2,3]
 [1,2,4]
(3 rows)

SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <=> '[0,0,0]') t2;
 count 
-------
     3
(1 row)

SELECT COUNT(*) FROM (SELECT * FROM t ORDER BY val <=> (SELECT NULL::halfvec)) t2;
 count 
-------
     3
(1 row)

DROP TABLE t;