Single Operator

Lantern adds experimental support for a single operator <?>. The operator has the following benefits

• One operator for all index queries
• Automatically detect when the operator is being used without an index

Setup

To enable the extension, set the runtime parameter lantern.pgvector_compat to FALSE. See below for an example, and see notes on Postgres configuration for more details on how to set this parameter.

SET lantern.pgvector_compat = FALSE;

Usage

You can create an index using the steps documented here. Then, at query time, you can just use the operator <?> to perform nearest neighbor search queries. Lantern will automatically infer the distance metric to use.

For example, you can create the following index.

CREATE INDEX
    book_index
ON
    books
USING
    hnsw (book_embedding dist_l2sq_ops)
WITH (
    M = 2,
    ef_construction = 10,
    ef = 4,
    dim = 3
);

Then, you can query the index like so:

SELECT title FROM books ORDER BY ARRAY[0,0,1] <?> book_embedding;

Note that the operator can only be used in an ORDER BY. For example, the following queries will not work

SELECT book_embedding <?> ARRAY[0,0,1] FROM books;
SELECT book_embedding <?> ARRAY[0,0,1] FROM books <?> book_embedding;