Enable docvalue_fields parameter for dense_vector fields

[mayya-sharipova]

Description

Search request supports docvalue_fields parameter that is currently not supported for dense_vector fields.

The reason it is was disabled is disable aggregations on this field. Investigate if is possible to keep aggregations still disabled but enable docvalue_fields on dense_vector fields.

[elasticsearchmachine]

Pinging @elastic/es-search (Team:Search)

[Rassyan]

Hello @mayya-sharipova,

I hope this message finds you well. I've been exploring the enhancement of dense_vector field values retrieval from doc_values and have a preliminary implementation in place. My initial tests indicate promising functionality.

Here are the key aspects of the current implementation:

• Introduction of a custom BinaryDocValues tailored for dense_vector fields.
• On-demand vector data loading to optimize memory efficiency.

I'm eager to ensure that this work aligns with the project's goals and would greatly appreciate your guidance on a couple of points:

• Could you suggest any performance benchmarks or specific use cases that the community is aiming to address with this feature?
• Would there be a preferred data format for the vectors that would best serve the needs of downstream processing?

I'm very interested in contributing to this feature and would be honored to incorporate your expertise as we refine the approach.

Thank you for considering my input.

Warm regards, Rassyan

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)