PgVector index declarations don't match

That's what caused this problem for me: https://github.com/zilliztech/VectorDBBench/issues/512

index: IndexType = IndexType.ES_IVFFlat

# ...

_pgvector_case_config = {
    IndexType.HNSW: PgVectorHNSWConfig,
    IndexType.ES_HNSW: PgVectorHNSWConfig,
    IndexType.IVFFlat: PgVectorIVFFlatConfig,
}

This makes it so that ivfflat is stored in the results but the key here has the value IVF_FLAT => 💥

Theoretically, I would recommend not just fixing that but also generally reworking the index values because there's also e.g.:

    HNSW = "HNSW"
# ...
    ES_HNSW = "hnsw"

Unfortunately, making changes to that would obviously break processing past results.

Start by locating the IndexType declarations and _pgvector_case_config mapping shown in the issue, then trace where index values are stored in results and where past results are read. Confirm the mismatch with a current pgvector case and check that any correction preserves processing of existing results; the issue does not name a test or file path.