pgvector compatibility

pgvecto.rs is natively compatible with pgvector at:

• CREATE TABLE commands, e.g. CREATE TABLE t (val vector(3))
• INSERT INTO commands, e.g. INSERT INTO t (val) VALUES ('[0.6,0.6,0.6]')

pgvecto.rs can be configured to be compatible with pgvector at:

• Index options, which allows you to create index by USING hnsw (val vector_ip_ops)
• Query options, which can be set by SET ivfflat.probes = 10

This feature is named pgvector compatibility. It can be enabled by SET vectors.pgvector_compatibility = on.

Index Options & Query Options

For index ivfflat and hnsw only the following options are available.

• Default value for index options is different from pgvecto.rs original, which keeps the same as in pgvector.
• Default value for query options is the same as in pgvecto.rs.

Index options for ivfflat:

Key	Type	Range	Default	Description
nlist	integer	[1, 1_000_000]	100	Number of cluster units.

Query options for ivfflat:

Option	Type	Range nn	Default	Description
ivfflat.probes	integer	[1, 1_000_000]	10	Number of lists to scan.

WARNING

Default value of ivfflat.probes is 10 instead of 1 from pgvector.

Index options for hnsw:

Key	Type	Range	Default	Description
m	integer	[4, 128]	16	Maximum degree of the node.
ef_construction	integer	[10, 2000]	64	Search scope in building.

Query options for hnsw:

Option	Type	Range	Default	Description
hnsw.ef_search	integer	[1, 65535]	100	Search scope of HNSW.

WARNING

Default value for hnsw.ef_search is 100 instead of 40 from pgvector.

Examples

It's easy to enable pgvector compatibility and start a vector query.

DROP TABLE IF EXISTS t;
SET vectors.pgvector_compatibility=on;
SET hnsw.ef_search=40;
CREATE TABLE t (val vector(3));
INSERT INTO t (val) SELECT ARRAY[random(), random(), random()]::real[] FROM generate_series(1, 1000);
CREATE INDEX hnsw_cos_index ON t USING hnsw (val vector_cosine_ops);
SELECT COUNT(1) FROM (SELECT 1 FROM t ORDER BY val <-> '[0.5,0.5,0.5]' limit 100) t2;
DROP INDEX hnsw_cos_index;

Multiply types of indexes are accepted:

SET vectors.pgvector_compatibility=on;
SET hnsw.ef_search=40;
-- [hnsw + vector_l2_ops] index with default options
CREATE INDEX hnsw_l2_index ON t USING hnsw (val vector_l2_ops);
-- [hnsw + vector_cosine_ops] index with single ef_construction option
CREATE INDEX hnsw_cosine_index ON t USING hnsw (val vector_cosine_ops) WITH (ef_construction = 80);
-- anonymous [hnsw + vector_ip_ops] with all options
CREATE INDEX ON t USING hnsw (val vector_ip_ops) WITH (ef_construction = 80, m = 12);
SET ivfflat.probes=1;
-- [ivfflat + vector_l2_ops] index with default options
CREATE INDEX ivfflat_l2_index ON t USING ivfflat (val vector_l2_ops);
-- [ivfflat + vector_ip_ops] index with all options
CREATE INDEX ivfflat_ip_index ON t USING ivfflat (val vector_cosine_ops) WITH (nlist = 80);
-- anonymous [ivf + vector_ip_ops] with all options
CREATE INDEX ON t USING ivfflat (val vector_ip_ops) WITH (lists = 80)