bug: Can not create `ivf` and `vamana` index about pgvecto.rs

[usamoi]

Algorithms do not work well on empty tables. A known problem.

[BeautyyuYanli]

postgres=# CREATE TABLE items (
  id bigserial PRIMARY KEY,
  embedding vector(3) NOT NULL
);
CREATE TABLE
postgres=# INSERT INTO items (embedding)
VALUES ('[1,2,3]'), ('[4,5,6]');
INSERT 0 2
postgres=# CREATE INDEX ON items USING vectors (embedding l2_ops)
WITH (options = $$
capacity = 2097152
[vectors]
memmap = "disk"
[algorithm.ivf]
quantization = { product = { ratio = "x16" } }
$$);
########## stuck here ##############

Stuck when building ivf index, after inserting items.

[VoVAllen]

Can you try larger vector dim? 3 might have problem with x16 quantization?

[BeautyyuYanli]

Can you try larger vector dim? 3 might have problem with x16 quantization?

Doesn't work (dim 300).

[usamoi]

Completed by #117.