Search

Get the nearest 5 neighbors to a vector

SET vectors.hnsw_ef_search = 64;
SELECT * FROM items ORDER BY embedding <-> '[3,2,1]' LIMIT 5;

Operators

These operators are used for distance metrics:

Name	Description
<->	squared Euclidean distance
<#>	negative dot product
<=>	cosine distance

For their definitions, see overview.

Filter

For a given category, get the nearest 10 neighbors to a vector

SELECT 1 FROM items WHERE category_id = 1 ORDER BY embedding <#> '[0.5,0.5,0.5]' limit 10

Query options

Set ivf scan lists to 1 in session:

SET vectors.ivf_nprobe=1;

Set hnsw search scope to 40 in transaction:

SET LOCAL vectors.hnsw_ef_search=40;

For all options, refer to search options.

Search modes

There are two search modes: vbase and basic.

vbase

As the default search mode, vbase is suitable for most scenarios.

For how it works, refer to the thesis VBASE: Unifying Online Vector Similarity Search and Relational Queries via Relaxed Monotonicity.

basic

basic is behaviorally consistent with vector algorithm libraries such as faiss. It will be useful if you want to align them.

Enabling basic, you must respect these restrictions:

• Execute VACUUM after updates before searches.
• Search without filter