SET enable_seqscan = off;
CREATE TABLE t (val sparsevec);
INSERT INTO t (val) VALUES ('{}'), ('{0:1,1:2,2:3}'), ('{0:1,1:1,2:1}'), (NULL);
CREATE INDEX ON t USING hnsw (val sparsevec_l2_ops);
INSERT INTO t (val) VALUES ('{0:1,1:2,2:4}');
SELECT * FROM t ORDER BY val <-> '{0:3,1:3,2:3}';
      val      
---------------
 {0:1,1:2,2:3}
 {0:1,1:2,2:4}
 {0:1,1:1,2:1}
 {}
(4 rows)

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

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

TRUNCATE t;
SELECT * FROM t ORDER BY val <-> '{0:3,1:3,2:3}';
 val 
-----
(0 rows)

DROP TABLE t;
-- TODO move
CREATE TABLE t (val sparsevec);
INSERT INTO t (val) VALUES (array_fill(1, ARRAY[1001])::vector::sparsevec);
CREATE INDEX ON t USING hnsw (val sparsevec_l2_ops);
ERROR:  sparsevec cannot have more than 1000 non-zero elements for hnsw index
TRUNCATE t;
CREATE INDEX ON t USING hnsw (val sparsevec_l2_ops);
INSERT INTO t (val) VALUES (array_fill(1, ARRAY[1001])::vector::sparsevec);
ERROR:  sparsevec cannot have more than 1000 non-zero elements for hnsw index
DROP TABLE t;