Rerank In Table since v0.2.1

Like most indexes, VectorChord stores vectors in both the index and the table. Although vectors can also be fetched from the table, doing so is much slower than the default behavior.

Some disk-saving solutions, such as pgvectorscale, don't store vectors in the index to reduce storage. This may negatively affect query performance.

However, if you are short on disk space and don't care much about performance, you can enable rerank_in_table option in CREATE INDEX to reduce disk usage.

sql

CREATE INDEX ON items USING vchordrq (embedding vector_l2_ops) WITH (options = $$
residual_quantization = true
rerank_in_table = true
[build.internal]
lists = []
$$);

Then, all queries of this index will retrieve the original vectors from the table, with a much smaller index size.

Performance Trade-offs

Query performance⛔️: With the rerank_in_table option, the vchordrq index will experience a significant (about 30%-50%) increase in query latency
Index size✅: With rerank_in_table option, the vchordrq index will save about 50% of disk usage

WARNING

Prefetch does not work when rerank_in_table is enabled.

Rerank In Table since v0.2.1 ​

Performance Trade-offs ​

Rerank In Table since v0.2.1

Performance Trade-offs