Function l2_distance 

pub fn l2_distance<const N: usize, L, R>(
    left: impl IntoExpr<L>,
    right: impl IntoExpr<R>,
) -> Expr<f32>
where
    L: VectorExpr<N>,
    R: VectorExpr<N>,

Euclidean (L2) distance using pgvector’s <-> operator.

Lower is more similar.

ANN note:

• This form is operator-based and can use pgvector ivfflat/hnsw indexes for ORDER BY ... LIMIT nearest-neighbor queries.