How can I delay HNSW index construction until a segment reaches a target size?

Elastic Stack Elasticsearch
1

I’m trying to tune vector indexing behavior. Specifically, I want the first HNSW index for a segment to be built only after the segment reaches a certain size (e.g., X MB or Y vectors), instead of building small HNSW graphs early.

Is there any setting in Elasticsearch or Lucene that controls this threshold?
If not, is this behavior hardcoded, and would exposing such a knob be feasible?

2

This type of knob was added recently to Apache Lucene: https://github.com/apache/lucene/pull/14963

However, its currently not released. Once Apache Lucene does another release (10.4), we will update Elasticsearch, exposing this setting as a index mapping option for HNSW indices.